METHOD 557: DETERMINATION OF HALOACETIC ACIDS,

BROMATE, AND DALAPON IN DRINKING WATER BY ION

CHROMATOGRAPHY ELECTROSPRAY IONIZATION
TANDEM MASS SPECTROMETRY (IC-ESI-MS/MS)

Andrew W. Breidenbach Environmental Research Center

Cincinnati, Ohio

Office of Water (MLK 140) EPA Document No. 815-B-09-012 September 2009 www.epa.gov/safewater
METHOD 557 DETERMINATION OF HALOACETIC ACIDS, BROMATE, AND
DALAPON IN DRINKING WATER BY ION CHROMATOGRAPHY
ELECTROSPRAY IONIZATION TANDEM MASS SPECTROMETRY
(IC-ESI-MS/MS)

Version 1.0
September 2009

A. D. Zaffiro and M. Zimmerman (Shaw Environmental, Inc.)

B. V. Pepich (U.S. EPA, Region 10 Laboratory)
Rosanne W. Slingsby, R. F. Jack and Christopher A. Pohl (Dionex Corporation)
D. J. Munch (U.S. EPA, Office of Ground Water and Drinking Water)

TECHNICAL SUPPORT CENTER

OFFICE OF GROUND WATER AND DRINKING WATER
U. S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268

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 METHOD 557

DETERMINATION OF HALOACETIC ACIDS, BROMATE, AND DALAPON IN DRINKING

WATER BY ION CHROMATOGRAPHY ELECTROSPRAY IONIZATION TANDEM MASS
SPECTROMETRY (IC-ESI-MS/MS)

1. SCOPE AND APPLICATION

1.1 Method 557 is a direct-inject, ion chromatography, negative-ion electrospray ionization,

tandem mass spectrometry (IC-ESI-MS/MS) method for the determination of haloacetic acids
in finished drinking water. Bromate and dalapon (2,2-dichloropropionic acid) may be
measured concurrently with the haloacetic acids. Real time, chromatographic separation of
common anions in drinking water (matrix elimination) is a key feature of this method.
Acceptable method performance has been demonstrated for matrix ion concentrations of 320
mg/L chloride, 250 mg/L sulfate, 150 mg/L bicarbonate and 20 mg/L nitrate. Method 557
requires the use of MS/MS in Multiple Reaction Monitoring (MRM) mode to enhance
selectivity. Precision and accuracy data have been generated for the detection of nine
haloacetic acids, bromate, and dalapon in reagent water, synthetic sample matrix, and finished
drinking water from both ground water and surface water sources. The single laboratory
Lowest Concentration Minimum Reporting Level (LCMRL) has also been determined in
reagent water. Method 557 is applicable for the measurement of the following analytes:

Chemical Abstracts Services

Analyte Registry Number (CASRN)
Bromate (BrO3-) 15541-45-4 (BrO3- anion)
Bromochloroacetic acid (BCAA) 5589-96-8
Bromodichloroacetic acid (BDCAA) 71133-14-7
Chlorodibromoacetic acid (CDBAA) 5278-95-5
Dalapon 75-99-0
Dibromoacetic acid (DBAA) 631-64-1
Dichloroacetic acid (DCAA) 79-43-6
Monobromoacetic acid (MBAA) 79-08-3
Monochloroacetic acid (MCAA) 79-11-8
Tribromoacetic acid (TBAA) 75-96-7
Trichloroacetic acid (TCAA) 76-03-9

1.2 The chromatographic and MRM mass spectrometry conditions described in this method were
developed using commercially available IC-ESI-MS/MS systems.

1.3 The single laboratory LCMRL is the lowest spiking concentration such that the probability of
spike recovery in the 50% to 150% range is at least 99%. Single laboratory LCMRLs for the
analytes in this method ranged from 0.042 to 0.58 microgram per liter (μg/L), and are listed in
Table 5. The procedure used to determine the LCMRL is described elsewhere.1

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 1.4 Laboratories using this method are not required to determine LCMRLs, but they must
demonstrate that the Minimum Reporting Level (MRL) for each analyte meets the
requirements described in Section 9.2.4.

1.5 Detection Limit (DL) is defined as the statistically calculated minimum concentration that can
be measured with 99% confidence that the reported value is greater than zero.2 The DL is
dependent on sample matrix, fortification concentration, and instrument performance.
Determining the DL for analytes in this method is optional (Sect. 9.2.6). DLs for method
analytes fortified into reagent water ranged from 0.015 to 0.20 µg/L (Table 6).

1.6 This method is intended for use by analysts skilled in the operation of IC-ESI-MS/MS instru­
mentation and the interpretation of the associated data.

1.7 METHOD FLEXIBILITY – The laboratory is permitted to select IC columns, eluent

compositions, eluent suppression techniques, and ESI-MS/MS conditions different from those
utilized to develop the method. However, the basic chromatographic elements of the method
must be retained. In order to avoid the effects of matrix suppression, the method analytes
must be substantially resolved chromatographically from common anions in drinking water.
Samples must be analyzed by direct injection. Filtering and pretreatment by use of solid
phase extraction are not permitted. At a minimum, the four internal standards prescribed in
this method must be used. Changes may not be made to sample collection and
preservation (Sect. 8) or to the quality control (QC) requirements (Sect. 9). Method
modifications should be considered only to improve method performance. Modifications that
are introduced in the interest of reducing cost or sample processing time, but result in poorer
method performance, may not be used. In all cases where method modifications are proposed,
the analyst must perform the procedures outlined in the Initial Demonstration of Capability
(IDC, Sect. 9.2), verify that all QC acceptance criteria in this method (Tables 11 and 12) are
met, and verify method performance in a real sample matrix (Sect. 9.4).

NOTE: Single quadrupole instruments are not permitted.

2. SUMMARY OF METHOD

Residual chlorine present in drinking water samples is reacted with ammonium chloride to form
chloramines, effectively preventing chlorine-mediated formation of method analytes during
storage. In addition, the combined chlorine residual prevents microbial degradation in the sample.
Prior to analysis, isotopically enriched analytes (monochloroacetic acid-2-13C, monobromoacetic
acid-1-13C, dichloroacetic acid-2-13C, and trichloroacetic acid-2-13C) are added to the samples as
internal standards. An aliquot of the sample is injected without cleanup or concentration onto an
ion exchange column specifically designed to separate method analytes from the following
common anions (matrix components) in drinking water: chloride, carbonate, sulfate, and nitrate.
The matrix components in the column eluate are monitored via conductivity detection and then
diverted to waste; the analytes of interest are directed into the ESI-MS/MS system. Acetonitrile is
added post-column to enhance desolvation of the method analytes in the ESI interface. Each

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 method analyte is qualitatively identified via a unique mass transition, and the concentration is
calculated using the integrated peak area and the internal standard technique.

3. DEFINITIONS

3.1 ANALYSIS BATCH – A sequence of samples, analyzed within a 30-hour period, including
no more than 20 field samples. Each Analysis Batch must also include all required QC
samples, which do not contribute to the maximum field sample total of 20. The required QC
samples include:

Laboratory Reagent Blank (LRB),

Continuing Calibration Check (CCC) Standards,
Laboratory Fortified Sample Matrix (LFSM), and
Laboratory Fortified Sample Matrix Duplicate or Laboratory Duplicate (LFSMD or LD).

3.2 CALIBRATION STANDARD – An aqueous solution of the method analytes prepared from
the Primary Dilution Standard (Sect. 3.21) solution. The calibration standards are used to
calibrate the instrument response with respect to analyte concentration.

3.3 CONTINUING CALIBRATION CHECK – A calibration standard containing the method

analytes and internal standards, which is analyzed periodically to verify the accuracy of the
existing calibration.

3.4 DETECTION LIMIT (DL) – The minimum concentration of an analyte that can be
identified, measured, and reported with 99% confidence that the analyte concentration is
greater than zero. This is a statistical determination (Sect. 9.2.6), and accurate quantitation is
not expected at this level.

3.5 DIVERT WINDOW – The period of time during which the column eluate is directed to
waste for the purpose of diverting matrix components away from the ESI-MS/MS system.

3.6 ELUTION WINDOW – The period of time during which the column eluate is directed to the
ESI-MS/MS system for the purpose of measuring the method analytes.

3.7 INTERNAL STANDARD – A pure compound added to all standard solutions and samples
in a known amount. Each internal standard is assigned to a specific analyte or multiple
analytes, and is used to measure relative response.

3.8 ION SUPPRESSION/ENHANCEMENT – An observable loss or increase in analyte

response in complex (field) samples as compared to the response obtained in standard
solutions.

3.9 LABORATORY DUPLICATES (LDs) – Two sample aliquots (LD1 and LD2) taken in the
laboratory from a single sample bottle, and analyzed separately with identical procedures.
By cancelling variation contributed from sample collection, preservation, and storage

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 procedures, Laboratory Duplicates provide an estimate of precision associated specifically
with the analytical determination.

3.10 LABORATORY FORTIFIED BLANK (LFB) – An aliquot of reagent water, containing the
method preservative, to which known quantities of the method analytes are added. The LFB
is used during the IDC to verify method performance for precision and accuracy.

3.11 LABORATORY FORTIFIED SAMPLE MATRIX (LFSM) – An aliquot of a field sample to

which known quantities of the method analytes are added. The LFSM is processed and
analyzed as a sample, and its purpose is to determine whether the sample matrix contributes
bias to the analytical results.

3.12 LABORATORY FORTIFIED SAMPLE MATRIX DUPLICATE (LFSMD) – A second

aliquot of the field sample used to prepare the LFSM which is fortified and analyzed
identically to the LFSM. The LFSMD is used instead of the Laboratory Duplicate to assess
method precision when the method analytes are rarely found at concentrations greater than
the MRL.

3.13 LABORATORY FORTIFIED SYNTHETIC SAMPLE MATRIX (LFSSM) – Aliquots of the

Laboratory Synthetic Sample Matrix (Sect. 3.15) fortified with known quantities of the
method analytes. The LFSSM is analyzed at the beginning of each Analysis Batch to verify
that the matrix components elute within the divert windows, and to ensure that no portion of
an analyte peak is inadvertently diverted to waste. The LFSSM also serves as a QC sample
for the purpose of estimating precision and accuracy during the IDC.

3.14 LABORATORY REAGENT BLANK (LRB) – An aliquot of reagent water that contains the
preservative and internal standards. The LRB is used to determine if the method analytes or
other interferences are introduced from the laboratory environment, the reagents or
glassware, and to test for cross contamination.

3.15 LABORATORY SYNTHETIC SAMPLE MATRIX (LSSM) – For this method, the LSSM is
a solution of common anions prepared at high concentrations relative to their typical
occurrence in drinking water. Guidance for preparation of the LSSM is provided in Section
7.2.

3.16 LOWEST CONCENTRATION MINIMUM REPORTING LEVEL (LCMRL) – The single

laboratory LCMRL is the lowest spiking concentration such that the probability of spike
recovery in the 50% to 150% range is at least 99%.1

3.17 MATERIAL SAFETY DATA SHEETS (MSDS) – Written information provided by vendors
concerning a chemical’s toxicity, health hazards, physical properties, fire and reactivity data,
storage instructions, spill response procedures, and handling precautions.

3.18 MINIMUM REPORTING LEVEL (MRL) – The minimum concentration that can be
reported by a laboratory as a quantified value for the method analyte in a sample following
analysis. This concentration must meet the criteria defined in Section 9.2.4 and must be no

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 lower than the concentration of the lowest calibration standard for each method analyte. A
laboratory may be required to demonstrate a specific MRL by a regulatory body if this
method is being performed for compliance purposes.

3.19 MULTIPLE REACTION MONITORING (MRM) – A mass spectrometric technique in

which a precursor ion (Sect. 3.20) is first isolated, then subsequently fragmented into a
product ion(s) (Sect. 3.23). Quantitation is accomplished by monitoring a specific product
ion. As described in Section 10.2.2, MS parameters must be optimized for each precursor
ion and product ion.

3.20 PRECURSOR ION – The precursor ion is the gas-phase species corresponding to the method
analyte produced in the ESI interface. In MS/MS, the precursor ion is mass selected and
fragmented by collision-activated dissociation to produce distinctive product ions of smaller
mass/charge (m/z) ratio.

3.21 PRIMARY DILUTION STANDARD (PDS) – An aqueous solution containing the method
analytes (or internal standards) prepared from Stock Standard Solutions and diluted as
needed to prepare calibration standards and sample fortification solutions.

3.22 PROCEDURAL CALIBRATION – A calibration technique in which calibration standards

are processed through the entire method, including sample preparation and addition of
preservatives.

3.23 PRODUCT-ION – For the purpose of this method, a product ion is one of the fragment ions
produced in MS/MS by collision-activated dissociation of the precursor ion.

3.24 QUALITY CONTROL SAMPLE (QCS) – A solution containing the method analytes at a
known concentration, which is obtained from a source external to the laboratory and different
from the source of calibration standards. The purpose of the QCS is to verify the accuracy of
the primary calibration standards.

3.25 REAGENT WATER – Purified water that does not contain any measurable quantity of the
method analytes or interfering compounds at or above 1/3 the MRL.

3.26 STOCK STANDARD SOLUTION (SSS) – A concentrated solution containing one or more
of the method analytes that is prepared in the laboratory using assayed reference materials or
purchased from a reputable commercial source, so that the concentration and purity of
analytes are traceable to certificates of analysis.

4. INTERFERENCES

4.1 GLASSWARE – During method development, no problems with stability of the method
analytes, interferences, or cross contamination related to glass containers were observed.
Sample collection bottles and vials containing samples and standards may be reused after
thorough rinsing with reagent water. Dry glassware in an oven or air dry. Teflon-faced
septa, if not punctured, may be cleaned and reused. Vials containing PDS solutions must be

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 rinsed with methanol before reuse and the septa discarded. It is recommended that
autosampler vials and septa be discarded after a single use.

4.2 REAGENTS AND EQUIPMENT – Method interferences may be caused by contaminants in

solvents and reagents (including reagent water). All laboratory reagents must be routinely
demonstrated to be free from interferences (less than 1/3 the MRL for the method analytes)
under the conditions of the analysis. This may be accomplished by analyzing LRBs as
described in Section 9.3.1.

4.3 MATRIX INTERFERENCES – Matrix interferences are caused by contaminants that are
present in the sample. The extent of matrix interferences will vary considerably from source
to source depending upon the nature of the water. Matrix components may directly interfere
by producing a signal at or near the retention time of an analyte peak. Matrix components
may also suppress or enhance the signal of the method analytes. (Suppression and
enhancement effects occur during the ionization process in the electrospray source when a
co-eluting contaminant influences the ionization of the analyte of interest.) Common anions
present in drinking water matrices, which would cause matrix suppression, are diverted from
the MS. In addition, the internal standards recommended in this method performed well in a
variety of matrices. However, these measures may not compensate for all potential matrix
effects. The analysis of Laboratory Fortified Sample Matrix (Sect. 9.3.5) provides evidence
for the presence (or absence) of matrix effects.

4.4 INTERFERENCE FROM SYSTEM CONTAMINANTS – Contaminants in the mobile

phase, autosampler, column, or other system components may produce a signal at or near the
retention time of a method analyte. Such an interfering signal may be observed as a shoulder
on an analyte peak or detected as an analyte peak in the Laboratory Reagent Blank. If this
occurs, attempt to eliminate the interference. If unsuccessful, investigate alternate MRM
transitions.

4.5 INTERFERENCE FROM INTERNAL STANDARDS – Depending on the source and

purity, labeled haloacetic acid internal standards may contain a small percentage of the
corresponding native analyte. Usually, such contributions are insignificant when performing
the method within the normal calibration range of 0.25 to 20 μg/L. However, the
contribution may be significant when attempting to determine LCMRLs and DLs. The
labeled internal standards must meet the purity requirements stated in the IDC (Section
9.2.1).

4.6 BREAKDOWN OF DALAPON, CDBAA, AND TBAA IN AQUEOUS MEDIA – Under

the conditions described in Section 8, the method analytes are stable in aqueous media within
the stated holding time. However, during method development, dalapon, CDBAA, and
TBAA—in both standards and drinking water samples—degraded while awaiting analysis in
conventional autosamplers that may reach temperatures between 25° and 30 °C during
operation. For this reason, refrigerated autosamplers, capable of maintaining samples at a
temperature of less than or equal to 10 °C, are required for use with Method 557.

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4.7 ION SUPPRESSION IN THE PRESENCE OF CHLORITE – The chlorite anion (ClO2-) may
be present in drinking water distribution systems employing chlorine dioxide (ClO2) as a
disinfectant. During method development studies, severe signal suppression of MCAA and
excessive band broadening of the MCAA chromatographic peak profile were observed in the
presence of 1 mg/L ClO2-, the maximum contaminant level (MCL). As depicted in Figure 4,
the ClO2- anion co-eluted with MCAA. Method 557 is not applicable to drinking water
treated with ClO2 unless the laboratory demonstrates alternate chromatographic conditions
(other than those used to develop the method, Section 17, Table 1) that eliminate the
suppression. That is, chlorite must be resolved chromatographically from MCAA and the
other method analytes. Alternately, the laboratory must demonstrate that the chlorite anion is
not present in the sample matrix.

4.8 SIGNAL SUPPRESSION DUE TO EXCESSIVE BACKGROUND CONDUCTIVITY –

The ESI interface is sensitive to the background conductivity of column eluate. The analyst
should observe the background conductivity prior to starting an analysis sequence each day.
If using a concentration gradient, make this observation at the initial eluent concentration. At
the maximum concentration in the gradient, the background conductivity will increase
compared to the conductivity at the initial concentration. In this region of the chromatogram,
the potential for suppression from the background conductivity is greatest. Such suppression
may be evidenced by difficulty detecting TBAA, or by peak areas that are low compared to
historical values when the background conductivity was lower. Section 11.3.2 provides
guidance on corrective action if background conductivity is problematic.

4.9 PEAK TAILING – Peak tailing may be observed as the column ages. Peak tailing will limit
the analyst’s ability to separate matrix components from the method analytes. Peak tailing
should be minimal with a properly configured ion chromatography system when using a new
column. (See Figure 2.) If tailing is observed with continued column use, original
performance can usually be restored by replacing the guard column.

4.10 EFFECT OF TEMPERATURE ON ANALYTE STABILITY – MBAA CDBAA, and TBAA

degrade readily in aqueous eluent at high pH. Such conditions may exist in the mobile phase
of ion exchange columns. The reaction is temperature dependent. For this reason, the
separation is performed at subambient temperature, specifically 15 °C. At 15 °C,
degradation in the column eluent is minimized.

4.11 MANAGING DIVERT WINDOWS – Analyte retention times may slowly shift toward
lower values as the column ages or becomes fouled. Because this method employs multiple
divert windows, the analyst must monitor peak locations on a daily basis to ensure that each
analyte peak elutes entirely within the MS/MS elution windows. Guidance for verifying
elution/divert windows is provided in Section 10.2.5. To avoid loss of column capacity,
follow the manufacturer’s instructions for proper operating temperature and for storage
conditions when the column is not in use.

4.12 BAND BROADENING AND RETENTION TIME (RT) SHIFTS IN HIGH IONIC
STRENGTH MATRICES – Method performance has not been evaluated for matrix ion
concentrations exceeding 320 mg/L chloride, 250 mg/L sulfate, 150 mg/L bicarbonate and 20

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 mg/L nitrate. Near these limits, the analyte peaks will widen, peak height will decrease, and
retention times will decrease slightly. These effects are compound dependent, but affect all
analytes to some degree. Such effects were minimal in the drinking water matrices
evaluated, but were more pronounced in Laboratory Synthetic Sample Matrix. [Compare
Figure 3 (fortified tap water) and Figure 4 (fortified synthetic matrix).] Note that the
concentrations of common anions in the LSSM are at the limits listed above. This method
requires the analyst to verify method performance in LSSM during the IDC, and to verify
elution/divert windows on a daily basis in LFSSM to ensure that these windows are properly
set to compensate for the potential effects of high ionic strength matrices.

5. SAFETY

5.1 The toxicity and carcinogenicity of each reagent used in this method has not been precisely
defined. Each chemical should be treated as a potential health hazard and exposure to these
chemicals should be minimized. Each laboratory is responsible for maintaining an awareness
of OSHA regulations regarding safe handling of chemicals used in this method.3 The OSHA
laboratory standards can be found online at
http://www.osha.gov/SLTC/laboratories/standards.html. A reference file of MSDSs should be
made available to all personnel involved in the chemical analysis.

5.2 Pure standard materials and stock standard solutions of the method compounds should be
handled with suitable protection for skin, eyes, etc.4

6. EQUIPMENT AND SUPPLIES

References to specific brands or catalog numbers are included as examples only and do not imply
endorsement of the product. Such reference does not preclude the use of other vendors or
suppliers.

6.1 SAMPLE CONTAINERS – Amber glass bottles fitted with polytetrafluoroethylene (PTFE)
-lined screw caps with sufficient volume to allow preparation of all required sample and QC
aliquots.

6.2 VIALS FOR SAMPLE PREPARATION – Amber glass vials with PTFE/silicone septa for
use preparing field samples and QC samples. Forty-milliliter (mL) volatile organic analysis
(VOA) vials (I-Chem Cat. No. S146–0040 or equivalent) were used during method
development.
6.3 AUTOSAMPLER VIALS – Glass vials with PTFE/silicone septa.

6.4 MICRO SYRINGES – Suggested sizes include 50, 100, and 1000 microliters (µL).

6.5 VOLUMETRIC PIPETTES – Class A, for preparing calibration standards, and for measuring
aliquots of field samples and QC samples.
6.6 AUTOMATIC PIPETTE – Electronic, with polypropylene tips (Eppendorf Research Pro or
equivalent). An automatic pipette is recommended for fortifying samples with internal
standards.

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6.7 ANALYTICAL BALANCE – Capable of weighing to the nearest 0.0001 gram (g).

6.8 TOP-LOADING BALANCE – Capable of weighing to the nearest 0.01 g. A top-loading

balance and disposable pipettes may be used to measure aqueous sample volumes and to
prepare aqueous calibration standards.

6.9 DESOLVATION GAS – High-purity gas (nitrogen or zero-air) for use in the ESI interface.
The specific type of gas, purity and pressure requirements will depend on the instrument
manufacturer’s specifications.

6.10 COLLISION GAS – High-purity gas (nitrogen or argon) for use in the collision cell of the
mass spectrometer. The specific type of gas, purity, and pressure requirements will depend
on the instrument manufacturer’s specifications.

6.11 DISPOSABLE PASTEUR PIPETTES – Borosilicate glass, used to transfer samples to

autosampler vials and for sample preparation.

6.12 ION CHROMATOGRAPHY ELECTROSPRAY IONIZATION TANDEM MASS

SPECTROMETRY SYSTEM (IC-ESI-MS/MS) – The following specifications are based on
use of a Dionex Corporation AS24 ion exchange column and a hydroxide-based eluent
system. Other columns and eluent systems are permitted providing that the basic
chromatographic elements of the method are retained (Sect. 1.7).

6.12.1 IC SYSTEM WITH SUPPRESSED CONDUCTIVITY DETECTION – An analytical

system (Dionex ICS-3000 or equivalent) consisting of a refrigerated autosampler, pump
module, anion trap, guard column, anion separator column, a six-port injection valve,
sample loop, conductivity suppressor, conductivity detector, post-column divert valve,
and a data acquisition and management system. The laboratory must be able to acquire
and store conductivity data for the purpose of monitoring matrix components and
establishing elution/divert windows.

6.12.1.1 ELUENT GENERATION – Reagent-free electrolytic eluent generation (Dionex ICS­

3000 EG or equivalent) or manually prepared reagents may be used. Care must be
exercised with manually prepared hydroxide eluent to prevent formation of carbonate
in the eluent from exposure to the atmosphere, which could cause analyte retention
times to drift.

6.12.1.2 ANION TRAP – A continuously regenerated anion trap column (Dionex CR-ATC or
equivalent).

6.12.1.3 SAMPLE LOOP – 100-µL size. A 100-µL sample loop was used to generate the data
presented in this method. Smaller injection volumes may be used as long as the
Initial Demonstration of Capability (Sect. 9.2), calibration, and sample analyses are
performed using the same injection volume. The laboratory must be able to meet the
MRL verification criteria (Section 9.2.4) using the selected injection volume.

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 6.12.1.4 GUARD COLUMN – IonPac® AG24, 2 x 50 millimeters (mm) (Dionex Part
No. 064151 or equivalent). The guard column is generally packed with the same
resin as the analytical column.

6.12.1.5 ANALYTICAL COLUMN – IonPac® AS24, 2 x 250 mm (Dionex Part No. 064153
or equivalent). Any column that provides on-line separation of common anions
(chloride, carbonate, sulfate, and nitrate) from the method analytes and symmetrical
peak shapes may be used. The column must have sufficient capacity to minimize
retention time shifts in high ionic strength matrices.

6.12.1.6 COLUMN COMPARTMENT – Temperature controlled and capable of subambient

operation.

6.12.1.7 CONDUCTIVITY SUPPRESSOR – An electrolytic suppressor operated with an

external source of regeneration water (Dionex Anion Self Regenerating Suppressor
Model No. ASRS®-300, 2-mm, Part No. 064555 or equivalent). Chemical
conductivity suppressors, although not prohibited, have not been evaluated for use
with Method 557.

6.12.1.8 CONDUCTIVITY DETECTOR – A flow-through detector with an internal volume

that does not introduce analyte band broadening.

6.12.1.9 POST-COLUMN DIVERT VALVE – A two-position, six-port valve may be used.

All wetted parts must be of polyetheretherketone (PEEK) construction. The proper
placement of the divert valve in the sample path is illustrated in Figure 1.

6.12.2 AUXILIARY PUMP – Pump capable of precisely delivering flow rates between 0.2 and
0.3 mL/minute. This pump is used to mix acetonitrile into the suppressed eluent post-
column. (Dionex high performance metering pump, Model No. AXP-MS or equivalent).
See Figure 1 for placement of the pump in the sample path.

6.12.3 STATIC MIXING TEE – High pressure, microbore mixing tee. (Upchurch Scientific,
Oak Harbor, WA, Part No. U-466 or equivalent). The proper placement of the mixing tee
in the sample path is illustrated in Figure 1.

6.12.4 ELECTROSPRAY IONIZATION – TANDEM MASS SPECTROMETER (ESI –

MS/MS) – The mass spectrometer interface must be able to operate in the negative-ion
electrospray ionization mode. The system must be capable of performing MS/MS to
produce unique product ions for the method analytes within specified retention time
windows. Method performance data presented in Section 17 were collected using a
Waters Quattro Premier XE ESI-MS/MS system.

6.12.5 MS/MS DATA SYSTEM – An interfaced data system is required to acquire, store, and
output MS data. The computer software must have the capability of processing stored
data by recognizing a chromatographic peak within a given retention time window. The
software must allow integration of the ion abundance of any specific ion between

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 specified time or scan number limits. The software must be able to construct a linear
regression or quadratic calibration curve and calculate analyte concentrations using the
internal standard technique.

7. REAGENTS AND STANDARDS

7.1 REAGENTS AND SOLVENTS – Reagent grade or better chemicals must be used. Unless
otherwise indicated, it is intended that all reagents will conform to the specifications of the
Committee on Analytical Reagents of the American Chemical Society (ACS), where such
specifications are available. Other grades may be used if all the requirements of the IDC are
met when using these reagents.

7.1.1 ACETONITRILE (CAS No. 75-05-8) – Post-column organic modifier. High purity,
demonstrated to be free of analytes and interferences (Honeywell Burdick & Jackson
Brand®, Catalog No. 015 or equivalent).

7.1.2 METHYL-TERTIARY-BUTYL ETHER (MtBE, CAS No. 1634-04-4) – High-

performance liquid chromatography-grade (Sigma-Aldrich Catalog No. 34875 or
equivalent). MtBE is used to prepare dilutions of neat standard materials.

7.1.3 AMMONIUM CHLORIDE (NH4Cl, CAS No. 12125-02-9) – Method preservative.

7.1.4 SODIUM BICARBONATE (CAS No. 144-55-8) – Laboratory Synthetic Sample Matrix
component.

7.1.5 SODIUM CHLORIDE (CAS No. 7647-14-5) – Laboratory Synthetic Sample Matrix
component.

7.1.6 SODIUM NITRATE (CAS No. 7631-99-4) – Laboratory Synthetic Sample Matrix
component.

7.1.7 SODIUM SULFATE (CAS No. 7757-82-6) – Laboratory Synthetic Sample Matrix
component.

7.2 LABORATORY SYNTHETIC SAMPLE MATRIX (LSSM) – Prepare the LSSM at the
concentrations listed in the table below. The required concentrations of nitrate (20 mg/L),
bicarbonate (150 mg/L), chloride (250 mg/L), and sulfate (250 mg/L) are based on the mass
of the anion, not the sodium salt. The NH4Cl preservative is included in the matrix. LFSSM
QC samples (Sect. 3.13) can be prepared by diluting the Analyte PDS (Sect. 7.3.2.2) with the
synthetic matrix solution.

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 Empirical Salt Anion Salt Mass Conc. Stock Conc. LSSM
Compound Formula (gfw)a (gfw) (mg) H2O, L (mg/L)b (mg/L)c
Ammonium chloride
NH4Cl 53.49 500 1000 100
(preservative)
-
Nitrate anion NO3 84.99 62.00 137 200 20
0.5
Bicarbonate anion HCO3- 84.01 61.02 1030 1500 150
Chloride anion Cl­ 58.44 35.45 2060 2500 250
Sulfate anion SO4-­ 142.04 96.06 1850 2500 250
a
gfw = gram formula weight of the sodium salt.
b
Stock concentration = (salt mass)(gfw anion)/(gfw salt)(0.5 L).
c
1:10 dilution of stock (e.g., 50 mL to 500 mL), LSSM = Laboratory Synthetic Sample Matrix.

7.3 STANDARD SOLUTIONS – Solution concentrations listed in this section were used to
develop this method and are included only as examples. Guidance on the storage stability of
Primary Dilution Standards and calibration standards is provided in the applicable sections
below.
NOTE: When preparing aqueous solutions from MtBE stock solutions, do not add more
than 0.5% of MtBE relative to the total water volume. MtBE has limited water solubility
(~5%).

7.3.1 INTERNAL STANDARDS – This method requires four isotopically enriched internal
standards. The following table lists the required internal standards and current sources.

Neat Materials Solution Standards

a
Internal Standard CASRN Catalog No. (1000 µg/mL in MtBE), Cat. No.
Monochloroacetic acid-2­ 13C 1633-47-2 Sigma-Aldrich 488526 Dionex Corp. 069406
13
Monobromoacetic acid-1­ C 57858-24-9 Sigma-Aldrich 279331 Dionex Corp. 069407
Dichloroacetic acid-2­ 13C 286367-78-0 Sigma-Aldrich 485489 Dionex Corp. 069408
Trichloroacetic acid-2­ 13C Not available Custom synthesisb Dionex Corp. 069409
a
CASRN = Chemical Abstract Registry Number.
b
Isotec, a member of the Sigma-Aldrich Group (www.sigma-aldrich.com/isotec).

NOTE: TCAA[1-13C] may NOT be substituted for TCAA[2-13C]. TCAA[1-13C] has been
demonstrated to convert to the native TCAA analyte in the ESI interface, theoretically via gas-
phase exchange with carbon dioxide-12C in the ionization region of the source. The process is
temperature dependent (desolvation gas temperature) and was observed on all MS/MS
platforms evaluated during method development.

7.3.1.1 INTERNAL STANDARD STOCK STANDARDS (ISSS) (1000 µg/mL) – Prepare

individual solutions of MCAA[2-13C], MBAA[1-13C], DCAA[2-13C], and TCAA[2­
13
C] by weighing 15 mg of the solid material into a 15-mL vial and adding 15 mL of
MtBE. Alternately, obtain the internal standards from outside suppliers as solutions
in MtBE at 1000 µg/mL.

7.3.1.2 INTERNAL STANDARD PRIMARY DILUTION STANDARD (Internal Standard

PDS) (1.0 µg/mL) – Prepare the Internal Standard PDS by adding enough of each
ISSS to a known volume of reagent water to make the final concentration 1.0 µg/mL
(e.g., combine 100 µL of each ISSS into 100 mL reagent water). Store the PDS in a

557-13
 glass vial with a PTFE/silicone septum. During method development, addition of 160
µL of the Internal Standard PDS to each 40-mL field sample, QC sample, or
calibration standard produced a final concentration of 4.0 µg/L. Analysts are
permitted to use other PDS concentrations and volumes provided all field samples,
QC samples, and calibration standards contain the same amount of internal standard,
the concentration of the internal standard added provides adequate signal to maintain
precision (as defined in the IDC), and the volume added has a negligible effect on the
final concentration. The aqueous Internal Standard PDS is stable for 60 days when
stored at 4 °C.

7.3.2 ANALYTE STANDARD SOLUTIONS

7.3.2.1 ANALYTE STOCK STANDARD SOLUTION (1000 µg/mL) – Obtain the

haloacetic acid analytes listed in the table in Section 1.1 as certified solutions in
MtBE. Obtain bromate as a certified aqueous standard. Obtain dalapon as a certified
standard in MtBE or in methanol. Representative sources are listed in the table in
Section 7.3.2.2.

7.3.2.2 ANALYTE PRIMARY DILUTION SOLUTION (Analyte PDS) (1.0 µg/mL) –

Prepare the Analyte PDS by diluting of the Analyte Stock Standard solutions into
reagent water. Store the PDS in a glass vial with a PTFE/silicone septum. The
Analyte PDS is used to prepare calibration standards, and to fortify QC samples with
the method analytes. An example preparation of the Analyte PDS that was used to
collect data presented in Section 17 is provided in the table below.

Stock Stock Final Volume Analyte PDS

Analyte Catalogue Concentration Volume (mL reagent Concentration
Stock Number (μg/mL) (mL) water) (μg/mL)
Bromate, Ultra Scientific 1000 as bromate
0.05
aqueous Cat. No. ICC-010 anion
Dalapon in Ultra Scientific
100 0.50
methanol Cat. No. HB-140
50 1.0
Haloacetic
acids in Restek Cat.
1000 0.05
methyl-tert­ No. 31896
butyl ether

NOTE: Storage stability of the Analyte PDS was evaluated during method
development at a single concentration of 1.0 µg/mL. The aqueous Analyte PDS is
stable for 60 days when stored at 4 °C. Other PDS concentrations may be selected.
However, it is recommended that the laboratory independently assess the stability of
the aqueous PDS to determine safe storage time.

7.3.2.3 CALIBRATION STANDARDS – This method uses a procedural calibration

technique. Prepare procedural calibration standards by diluting the Analyte PDS into
reagent water containing 100 mg/L NH4Cl (preservative). A calibration range of 0.25
to 20 μg/L is recommended as a starting point and is adequate for most drinking
water sources. The lowest concentration calibration standard must be at or below the

557-14
 MRL. A constant amount of each internal standard is added to each calibration
standard. The calibration standards may also be used as CCCs. An example of the
dilutions (starting with the Analyte PDS) necessary to prepare the calibration
standards is provided in the table below.

Starting Final Volume (mL, Final Internal Standard

Concentration 100 mg/L ammonium Concentration Concentrationa
Dilution Aliquot (μg/L) chloride, aqueous) (μg/L) (μg/L)
2 mL Analyte PDS 1000 50 40 (WS)a 4.0
20 mL of WS 40 40 20 4.0
10 mL of WS 40 40 10 4.0
5 mL of WS 40 40 5.0 4.0
2 mL of WS 40 40 2.0 4.0
1 mL of WS 40 40 1.0 4.0
4 mL of 5 μg/L std. 5.0 40 0.50 4.0
2 mL of 5 μg/L std. 5.0 40 0.25 4.0
a
Internal standards added at the rate of 160 μL to 40 mL by use of an Eppendorf Research Pro pipette:
(0.16 mL)(1.0 μg/mL)/(0.040 liter) = 4.0 μg/L internal standard concentration
b
WS = working standard; not analyzed.

NOTE: The stability of calibration standards was evaluated during method

development at concentrations of 2.0 and 5.0 μg/L. The aqueous calibration
standards are stable for 14 days when stored at 4 °C in glass vials with PTFE/silicone
septa. It is recommended that the laboratory independently assess the stability of the
aqueous calibration standards to determine safe storage time.

8. SAMPLE COLLECTION, PRESERVATION, AND STORAGE

The preservation requirements for Method 557 are identical to those stipulated in EPA Method
552.3, Determination of Haloacetic Acids and Dalapon in Drinking Water by Liquid-Liquid
Microextraction, Derivatization, and Gas Chromatography with Electron Capture Detection.5

8.1 SAMPLE BOTTLE PREPARATION

8.1.1 SAMPLE CONTAINERS – Amber glass bottles with PTFE-lined screw caps and
sufficient capacity to allow subsequent preparation of all required sample and QC
aliquots.

8.1.2 ADDITION OF PRESERVATIVE – Prior to shipment to the field, add crystalline or

granular NH4Cl to the sample containers to produce a concentration of 100 mg/L in the
field sample. For example, a 250-mL sample requires 25 mg of NH4Cl.

8.2 SAMPLE COLLECTION – Grab samples must be collected in accordance with conventional
sampling practices.6 Fill sample bottles taking care not to flush out the ammonium chloride.
Because the method analytes are not volatile, it is not necessary to ensure that the sample
bottles are completely headspace-free.

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 8.2.1 SAMPLING FROM A TAP – When sampling from a cold water tap, remove the aerator,
open the tap, and allow the system to flush until the water temperature has stabilized
(approximately three to five minutes). Collect a representative sample from the flowing
system using a beaker of appropriate size. Use this bulk sample to generate individual
samples as needed. Invert the vials several times to mix the sample with the preservation
reagent.

8.3 SAMPLE SHIPMENT AND STORAGE – Samples must be chilled during shipment and
must not exceed 10 °C during the first 48 hours after collection. Samples must be confirmed
to be at or below 10 °C when they are received at the laboratory. In the laboratory, samples
must be stored at or below 6 °C and protected from light until analysis. Samples must not be
frozen.

8.4 SAMPLE HOLDING TIMES – Samples must be analyzed within 14 days of collection.
Chlorinated field samples that are preserved in accordance with the method guidance should
not exhibit biological degradation of analytes during the allotted 14-day storage time. The
residency time in the autosampler must be included when calculating the holding time
from collection until analysis.

9. QUALITY CONTROL

9.1 QC requirements include the IDC and ongoing QC requirements. This section describes each
QC parameter, its required frequency, and the performance criteria that must be met in order
to satisfy EPA quality objectives. The QC criteria discussed in the following sections are
summarized in Section 17, Tables 11 and 12. These QC requirements are considered the
minimum acceptable QC program. Laboratories are encouraged to institute additional QC
practices to meet their specific needs.

9.2 INITIAL DEMONSTRATION OF CAPABILITY (IDC) – The IDC must be successfully

performed prior to analyzing any field samples. The IDC must be repeated if changes are
made to analytical parameters not previously validated during the IDC, for example, selection
of an alternate MRM transition or changing the internal standard assignment of an analyte.
Prior to conducting the IDC, the analyst must verify proper timing of elution windows and
divert windows (Section 10.2.5), and meet the calibration requirements outlined in Sections
10.2 and 10.3.

9.2.1 DEMONSTRATION OF LOW SYSTEM BACKGROUND – Analyze an LRB.

Confirm that the blank is free of contamination as defined in Section 9.3.1.

NOTE: Depending on the source and purity, labeled haloacetic acid internal standards
may contain a small percentage of the corresponding native analyte. Therefore, the
analyst must demonstrate that the internal standards do not contain the unlabeled analytes
at a concentration >1/3 of the MRL when added at the appropriate concentration to
samples. An internal standard concentration of 4.0 µg/L was used during method
development. Lower concentrations may be used providing the internal standard QC
criteria (Sect. 9.3.4) are met.

557-16
 NOTE: The method must be checked for cross contamination (commonly referred to in
the environmental laboratory community as “carryover”) by analyzing an LRB
immediately following the highest calibration standard. If this LRB does not meet the
criteria outlined in Section 9.3.1, then carryover is present and the cause must be
identified and eliminated.

9.2.2 DEMONSTRATION OF PRECISION – Prepare and analyze seven replicate LFBs and
seven replicate LFSSMs. Fortify these samples near the midrange of the initial
calibration curve. The NH4Cl preservative must be added to the LFBs as described in
Section 8.1.2. The percent relative standard deviation (RSD) of the concentrations of the
replicate analyses must be ≤20% for all method analytes.

Standard Deviation of Measured Concentrations

% RSD = ×100
Average Concentration

9.2.3 DEMONSTRATION OF ACCURACY – Using the same sets of replicate data generated
for Section 9.2.2, calculate the average percent recovery. The average percent recovery
of the replicate analyses must be within +30% of the true value.

Average Measured Concentration

% Recovery = ×100
Fortified Concentration

9.2.4 MINIMUM REPORTING LEVEL (MRL) CONFIRMATION – Establish a target

concentration for the MRL based on the intended use of the method. Analyze an initial
calibration following the procedures in Section 10.3. The lowest calibration standard
used to establish the initial calibration (as well as the low-level CCC) must be at or below
the concentration of the MRL. Establishing the MRL concentration too low may cause
repeated failure of ongoing QC requirements. Confirm the MRL following the procedure
outlined below.

9.2.4.1 Fortify and analyze seven replicate LFBs at or below the proposed MRL
concentration. The LFBs must contain the method preservative as specified in
Section 8.1.2. Calculate the mean (Mean) and standard deviation for these replicates.
Determine the Half Range for the Prediction Interval of Results (HRPIR) using the
equation

HRPIR = 3.963S

where S is the standard deviation and 3.963 is a constant value for seven replicates.1

9.2.4.2 Confirm that the Upper and Lower limits for the Prediction Interval of Results (PIR =
Mean + HRPIR) meet the upper and lower recovery limits as shown below.

The Upper PIR Limit must be ≤150 percent recovery.

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 Mean + HR PIR
× 100 ≤ 150%
Fortified Concentration

The Lower PIR Limit must be ≥50 percent recovery.

Mean − HR PIR
× 100 ≥ 50%
Fortified Concentration

9.2.4.3 The MRL is validated if both the Upper and Lower PIR Limits meet the criteria
described above. If these criteria are not met, the MRL has been set too low and must
be confirmed again at a higher concentration.

NOTE: These equations are only valid for seven replicate samples.

9.2.5 QUALITY CONTROL SAMPLE (QCS) – Analyze a mid-level Quality Control Sample
(Sect. 9.3.7) to confirm the accuracy of the primary calibration standards.

9.2.6 DETECTION LIMIT DETERMINATION (optional) – While DL determination is not a

specific requirement of this method, it may be required by various regulatory bodies
associated with compliance monitoring. It is the responsibility of the laboratory to
ascertain whether DL determination is required based upon the intended use of the data.

Analyses for this procedure must be done over at least three days. Prepare at least seven
replicate LFBs at a concentration estimated to be near the DL. This concentration may be
estimated by selecting a concentration at two to five times the noise level. The NH4Cl
preservative must be added to the samples as described in Section 8.1.2. Process the
seven replicates through all steps of Section 11.

NOTE: If an MRL confirmation data set meets these requirements, a DL may be

calculated from the MRL confirmation data, and no additional analyses are necessary.

Calculate the DL using the following equation:

DL = S x t(n-1,1-α = 0.99)

where
t(n-1,1-α = 0.99) = Student's t value for the 99% confidence level with n-1 degrees of
freedom (for seven replicate determinations, the Student’s t value
is 3.143 at a 99% confidence level),
n = number of replicates, and
S = standard deviation of replicate analyses.

NOTE: Do not subtract blank values when performing DL calculations.

557-18
9.3 ONGOING QC REQUIREMENTS – This section describes the ongoing QC elements that
must be included when processing and analyzing field samples. Table 12 summarizes these
requirements.

9.3.1 LABORATORY REAGENT BLANK (LRB) – Analyze an LRB during the IDC and
with each Analysis Batch. The LRB must contain the NH4Cl preservative and the
internal standards at the same concentration used to fortify all field samples and
calibration standards. Background from method analytes or contaminants that interfere
with the measurement of method analytes must be <1/3 the MRL. If method analytes are
detected in the LRB at concentrations equal to or greater than this level, then all data for
the problem analyte(s) must be considered invalid for all samples that yielded a positive
result. Subtracting blank values from sample results is not permitted.

NOTE: Although quantitative data below the MRL may not be accurate enough for data
reporting, such data are useful in determining the magnitude of background interference.
Therefore, blank contamination levels may be estimated by extrapolation when the
concentration is below the MRL.

9.3.2 CONTINUING CALIBRATION CHECK (CCC) – Analyze CCC standards at the

beginning of each Analysis Batch, after every ten field samples, and at the end of the
Analysis Batch. See Section 10.4 for concentration requirements and acceptance criteria
for CCCs.

9.3.3 LABORATORY FORTIFIED BLANK (LFB) – Because this method utilizes procedural
calibration standards, which are fortified reagent waters, there is no difference between
the LFB and the Continuing Calibration Check standard. Consequently, the analysis of a
separate LFB is not required as part of the ongoing QC; however, the term “LFB” is used
for clarity in the IDC.

9.3.4 INTERNAL STANDARDS (IS) – The analyst must monitor the peak areas of the
internal standards in all injections of the Analysis Batch. The internal standard responses
(as indicated by peak areas) for any chromatographic run must not deviate by more than
±50% from the average areas measured during the initial calibration for the internal
standards. If an IS area for a sample does not meet this criterion, check the
corresponding IS area of the most recent CCC and proceed as follows.

9.3.4.1 If the IS criterion is met in the CCC but not the sample, reanalyze the sample in a
subsequent Analysis Batch. If the IS area fails to meet the acceptance criterion in the
repeat analysis, but passes in the most recent CCC, report the sample results as
“suspect/matrix.”

9.3.4.2 If both the original field sample and the CCC fail the IS area criterion, take corrective
action (e.g., Sect. 10.4.3). After servicing the instrument, re-inject the sample in a
subsequent Analysis Batch. If the IS area fails to meet the acceptance criterion in the

557-19
 repeat analysis, but passes in the most recent CCC, report the sample results as
“suspect/matrix.”

9.3.5 LABORATORY FORTIFIED SAMPLE MATRIX (LFSM) – Within each Analysis

Batch, analyze a minimum of one LFSM. The background concentrations of the analytes
in the sample matrix must be determined in a separate aliquot and subtracted from the
measured values in the LFSM. If various sample matrices are analyzed regularly, for
example, drinking water processed from ground water and surface water sources,
performance data must be collected for each source.

9.3.5.1 Prepare the LFSM by fortifying a sample with an appropriate amount of the Analyte
PDS (Sect. 7.3.2.2). Generally, select a spiking concentration that is greater than or
equal to the native concentration for most analytes. If the native concentrations of
method analytes do not allow this criterion to be met without exceeding the
calibration range, dilution with reagent water containing NH4Cl (100 mg/L) is
permitted. Selecting a duplicate aliquot of a sample that has already been analyzed
aids in the selection of an appropriate spiking level. If this is not possible, use
historical data when selecting a fortifying concentration.

9.3.5.2 Calculate the percent recovery (%R) using the equation:

%R =
(A - B) ×100
C
where
A = measured concentration in the fortified sample,
B = measured concentration in the unfortified sample, and
C = fortification concentration.

9.3.5.3 Recoveries for samples fortified at concentrations near or at the MRL (within a factor
of two times the MRL concentration) must be within +50% of the true value.
Recoveries for samples fortified at all other concentrations must be within +30% of
the true value. If the accuracy for any analyte falls outside the designated range, and
the laboratory performance for that analyte is shown to be in control in the CCCs, the
recovery is judged matrix biased. Report the result for the corresponding analyte in
the unfortified sample as “suspect/matrix.”

NOTE: In order to obtain meaningful percent recovery results, correct the measured
values in the LFSM and LFSMD for the native levels in the unfortified samples, even
if the native values are less than the MRL. This situation and the LRB are the only
permitted uses of analyte results below the MRL.

9.3.6 LABORATORY DUPLICATE OR LABORATORY FORTIFIED SAMPLE MATRIX

DUPLICATE (LD or LFSMD) – Within each Analysis Batch, analyze a minimum of one
Laboratory Duplicate or one Laboratory Fortified Sample Matrix Duplicate. If the
method analytes are not routinely observed in field samples, analyze an LFSMD rather
than an LD.

557-20
 NOTE: The variation due to the addition of internal standards must be included in the
precision estimate. Therefore, first split the original sample and then fortify each aliquot
with internal standards.

9.3.6.1 Calculate the relative percent difference (RPD) for duplicate measurements (LD1 and
LD2) using the equation:

LD1 − LD 2
RPD = ×100
(LD1 + LD2 ) / 2
9.3.6.2 RPDs for Laboratory Duplicates must be ≤30%. Greater variability may be observed
when Laboratory Duplicates have analyte concentrations that are near or at the MRL
(within a factor of two times the MRL concentration). At these concentrations,
Laboratory Duplicates must have RPDs that are ≤50%. If the RPD of an analyte falls
outside the designated range, and the laboratory performance for the analyte is shown
to be in control in the CCC, the precision is judged matrix influenced. Report the
result for the corresponding analyte in the unfortified sample as “suspect/matrix.”

9.3.6.3 If an LFSMD is analyzed instead of a Laboratory Duplicate, calculate the RPD for the
LFSM and LFSMD using the equation:

LFSM − LFSMD
RPD = ×100
(LFSM + LFSMD)/2

9.3.6.4 RPDs for duplicate LFSMs must be ≤30%. Greater variability may be observed when
the matrix is fortified at analyte concentrations near or at the MRL (within a factor of
two times the MRL concentration). LFSMs at these concentrations must have RPDs
that are ≤50%. If the RPD of an analyte falls outside the designated range, and the
laboratory performance for the analyte is shown to be in control in the CCC, the
precision is judged matrix influenced. Report the result for the corresponding analyte
in the unfortified sample as “suspect/matrix.”

9.3.7 QUALITY CONTROL SAMPLE (QCS) – A QCS must be analyzed during the IDC, and
then at least quarterly thereafter. Fortify the QCS near the midpoint of the calibration
range. The acceptance criteria for the QCS are the same as the mid- and high-level CCCs
(Sect. 10.4). If the accuracy for any analyte fails the recovery criterion, prepare fresh
standard dilutions and repeat the QCS evaluation.

9.4 METHOD MODIFICATION QC REQUIREMENTS – The laboratory is required to perform

the procedures in this section if chromatographic conditions and a suppression technique are
selected which are different from those utilized to develop the method. Any proposed
method modifications must retain the basic chromatographic elements of this new technique
(Sect. 1.7). Examples of method modifications include alternate IC columns, an injection
volume less than 100 uL, and additional internal standards proposed for use with the method.

557-21
 9.4.1 Each time method modifications are made, optimize the elution gradient to accomplish
separation of the method analytes from matrix components, and then verify elution and
divert windows following the guidance in Section 10.2.5. Establish an acceptable initial
calibration (Sect. 10.3). Finally, repeat the procedures of the IDC (Sect. 9.2).

9.4.2 The analyst is also required to evaluate and document method performance for the
proposed modifications in real matrices that span the range of waters that the laboratory
analyzes. This additional step is required because modifications that perform acceptably
in the IDC, which is conducted in reagent water and synthetic matrix, could fail ongoing
method QC requirements in real matrices. This is particularly important for methods
subject to matrix effects, such as IC/MS-based methods. For example, a laboratory may
routinely analyze drinking water from municipal treatment plants that process ground
water, surface water, or a blend of surface and ground water. In this case, the method
modification requirement could be accomplished by assessing precision and accuracy
(Sects. 9.2.2 and 9.2.3) in a surface water with moderate to high total organic carbon
(e.g., 2 mg/L or greater) and a hard ground water (e.g., 250 mg/L as calcium carbonate
(CaCO3) equivalent, or greater).

9.4.3 The results of Sections 9.4.1 and 9.4.2 must be appropriately documented by the analyst
and independently assessed by the laboratory’s QA officer prior to analyzing field
samples. When implementing method modifications, it is the responsibility of the
laboratory to closely review the results of ongoing QC, and in particular, the results
associated with the LFSM (Sect. 9.3.5), LFSMD (Sect. 9.3.6), CCCs (Sect. 9.3.2), and
the internal standard area counts (Sect. 9.3.4). If repeated failures are noted, the
modification must be abandoned.

10 CALIBRATION AND STANDARDIZATION

10.1 Demonstration and documentation of acceptable MS calibration and initial analyte

calibration are required before performing the IDC and prior to analyzing field samples.
Prior to calibration, the analyst must verify the proper timing of divert windows as described
in Section 10.2.5. The initial calibration must be repeated each time a major instrument
modification or maintenance is performed.

10.2 IC-ESI-MS/MS CALIBRATION AND OPTIMIZATION

10.2.1 MASS CALIBRATION – Method 557 requires the monitoring of low-mass, negatively
charged ions within nominal m/z range of 35 to 251. Calibrate the mass spectrometer
with the calibration compounds and procedures specified by the manufacturer. Verify the
mass assignment accuracy for each precursor ion and each product ion by comparing the
reported centroid mass to the theoretical mass. (Pay particular attention to the chlorine
product ion at nominal m/z 35, actual m/z 34.97.) Low signal response could result if
mass assignments are not centered on the detected mass peaks. If the reported masses
differ from the calculated masses and low response is observed, the standard calibration
procedure may be inadequate for this method. Consult the MS/MS manufacturer for an

557-22
 appropriate low-mass calibration procedure. During method development, accurate mass
assignments were achieved after calibration via direct infusion of sodium formate
(10 nanograms per microliter) in 90:10 2-propanol:water, rather than the sodium iodide
and cesium iodide mixture typically employed for Waters MS/MS systems.

10.2.2 OPTIMIZING MS PARAMETERS – Each IC-ESI-MS/MS system will have different

optimal conditions, which are influenced by the source geometry and system design. Due
to the differences in design, follow the recommendations of the instrument manufacturer
when tuning the instrument. During the development of this method, instrumental
parameters were optimized for the precursor and product ions listed in Section 17, Table
3. Because the method analytes are relatively small molecules, the selection of precursor
and product ions is limited. However, transitions other than those listed exist, and the
optimum choice depends on the instrument platform as noted below.

NOTE: Several instrument platforms were investigated during method development.

The most abundant precursor ions differed depending on the design of the ESI interface.
In particular, the trihaloacetic acids containing bromine tend to undergo neutral loss in
the ESI interface. For example, the precursor ions for BDCAA, CDBAA, and TBAA
used during method development (Table 3) are 44 mass units less than the molecular ion,
corresponding to loss of a carboxyl group (COO-). However, using other ESI designs,
the m/z 207 precursor ion for BDCAA was observed, which corresponds to the mass of
the molecular ion. BDCAA and TBAA exhibited neutral loss on all ESI-MS/MS systems
evaluated. The most abundant product ions also differed between instruments. Although
the mass transitions in Table 3 are provided as a guide, the analyst must empirically
determine the most abundant precursor and product ions.

10.2.2.1 Optimize the ESI-MS/MS at the analytical flow rate (column eluent plus post-column
acetonitrile addition) via split infusion or flow injection analysis (FIA). Use solutions
having concentrations between 1 and 5 µg/mL of the method analytes in reagent
water for split infusion, and solutions having concentrations between 10 and 100 µg/L
(0.01 and 0.1 μg/mL) in reagent water for FIA. Five- or 10-μL sampling loops are
recommended for optimizing via FIA. Because the precursor and product ions may
be identical for some of the haloacetic acids, individual solutions of the method
analytes are recommended for this step.

10.2.2.2 Using Table 3 as a guide, select the most abundant precursor ion. Optimize the
response of the precursor ion for each analyte by infusing the prepared solutions
(Sect. 10.2.2.1) directly into mobile phase (or via FIA). Vary the ESI parameters
(probe orientation, capillary extension, source voltages, source and desolvation
temperatures, gas flows, etc.) and the MS parameters until optimal analyte responses
are determined. The method analytes may have different optima, thus requiring some
compromise. ESI-MS/MS systems are subject to drift, which can affect run-to-run
precision. Accordingly, the optimal conditions may be those that yield adequate
response while minimizing the potential for drift.

557-23
 10.2.2.3 Using Table 3 as a guide, select the most abundant product ion. Optimize the
response of the product ion for each analyte by infusing the prepared solutions (Sect.
10.2.2.1) directly into the mass spectrometer (or via FIA). Vary the MS/MS
parameters (collision gas pressure, collision energy, etc.) until optimal analyte
responses are determined.

10.2.3 ION CHROMATOGRAPHY INSTRUMENT CONDITIONS – Follow the column

manufacturer’s guidelines for calculating the elution gradient to accomplish separation of
the method analytes from matrix components. IC operating conditions for the Dionex
AS24 column7 used during method development are summarized in Section 17, Table 1.
Establish divert windows for the matrix components and elution windows for the method
analytes per the column manufacturer’s instructions. Figure 2 presents an example of
these windows optimized for the Dionex AS24 column. Conditions different from those
described in this method (e.g., IC columns and mobile phases) may be used if the QC
criteria in Sections 9.2, 9.3 and 9.4 are met, the column provides reasonable resolution of
the method analytes, and chromatographic separation of the method analytes from matrix
anions (chloride, carbonate, sulfate, nitrate) is achieved.

10.2.4 ESTABLISH IC-ESI-MS/MS RETENTION TIMES AND MRM SEGMENTS – Inject a

mid- to high-level calibration standard under optimized IC-ESI-MS/MS conditions to
obtain the retention times of each method analyte. Divide the chromatogram into
segments that contain one or more chromatographic peaks. For maximum sensitivity in
subsequent MS/MS analyses, minimize the number of MRM (Sect. 3.19) transitions that
are simultaneously monitored within each segment. Table 2 presents the assignment of
the method analytes and internal standards into each of the three MRM windows used
during method development.

10.2.5 VERIFY ELUTION AND DIVERT WINDOWS FOR MATRIX ELIMINATION –

Conduct the following tests and verify that the timing of the elution and divert windows
meet the stated criteria.

10.2.5.1 Stabilize the chromatographic system and analyze an LFSSM at 10 µg/L. Locate
the first and last analyte peak in each elution window. Display the corresponding
conductivity trace and note the peak start and peak end times for the chloride,
carbonate, sulfate, and nitrate matrix anions. Consider a conductivity signal of
~5 µS as the peak end (return to baseline) after elution of a matrix anion. [Refer to
figures 4 and 5 for an example based on use of the Dionex AS24 column. For this
column, the chloride anion elutes between elution window 1 and elution window 2.
Carbonate, sulfate and nitrate anions elute between elution windows 2 and 3.]

10.2.5.2 For the first analyte in each elution window, calculate a maximum time for the
preceding valve switch: RT – (1.5)(peak width at base of the first analyte in the
window). For the last analyte in each elution window, calculate a minimum time for
the following valve switch: RT + (1.5)(peak width at base of the last analyte in the
window). Verify that the valve switch times set in step 10.2.3 do not overlap the
calculated times.

557-24
 NOTE: The actual valve switch times are set in accordance with the column
manufacturer’s guidelines (Section 10.2.3). These could be wider than the start and
end times for the elution windows calculated using the equations in this section.

10.2.5.3 By inspection, verify that matrix peaks have returned to baseline before the
calculated valve switch at the beginning of each elution window. By inspection,
verify that the valve switch at the beginning of each divert window occurs before a
matrix component begins to elute. Finally, verify that each analyte elutes entirely
within the established elution windows. If these conditions are not met, consult the
column manufacturer’s guidelines for adjusting the elution gradient and reset the
timing of the divert valve accordingly.

NOTE: Enough time should be allowed for the baseline to stabilize between the
valve switch that begins each elution window and the appearance of the subsequent
analyte signal. If the valve switch is too close to the analyte, the starting point of
the analyte peak may be difficult to distinguish from the baseline disruption,
especially for low analyte concentrations.

10.3 INITIAL CALIBRATION

10.3.1 CALIBRATION STANDARDS – Prepare a set of at least five calibration standards as

described in Section 7.3.2.3. The analyte concentrations in the lowest calibration
standard must be at or below the MRL. Field samples must be quantified using a
calibration curve that spans the same concentration range used to collect the IDC data
(Sect. 9.2), i.e., analysts are not permitted to use a restricted calibration range to meet the
IDC criteria and then use a larger dynamic range during analysis of field samples.

10.3.2 CALIBRATION – Calibrate the IC-ESI-MS/MS system using peak areas and the internal
standard technique. Fit the calibration points with either a linear regression or quadratic
regression (response vs. concentration). Weighting may be used. Forcing the calibration
curve through the origin is not recommended. The MS/MS instrument used during
method development was calibrated using inverse concentration-weighted quadratic
curves.

NOTE: Internal standard assignments appropriate for the Dionex AS24 column for each
method analyte are presented in Table 3, and the mass transitions for the internal
standards are provided in Table 4. MCAA must always be referenced to MCAA[2-13C].
MBAA must always be referenced to MBAA[1-13C]. Method 557 was validated with
bromate referenced to MBAA[1-13C]; however, MCAA[2-13C] could be used if all
requirements in the IDC are met, as well as all ongoing QC requirements.

10.3.3 CALIBRATION ACCEPTANCE CRITERIA – Validate the initial calibration by

calculating the concentration of the analytes for each of the analyses used to generate the
calibration curve by use of the regression equations. Calibration points that are ≤MRL
must calculate to be within +50% of their true value. All other calibration points must

557-25
 calculate to be within +30% of their true value. If these criteria cannot be met, the
analyst will have difficulty meeting ongoing QC criteria. In this case, corrective action is
recommended such as reanalyzing the calibration standards, restricting the range of
calibration, or performing instrument maintenance.

10.4 CONTINUING CALIBRATION CHECKS (CCCs) – Analyze a CCC to verify the initial
calibration at the beginning of each Analysis Batch, after every tenth field sample, and at the
end of each Analysis Batch. The beginning CCC for each Analysis Batch must be at or
below the MRL. This CCC verifies instrument sensitivity prior to the analysis of samples.
Alternate subsequent CCCs between the remaining calibration levels.

10.4.1 Verify that the absolute areas of the quantitation ions of each of the internal standards
have not changed by more than ±50% from the average areas measured during the initial
calibration. If this limit is exceeded, verify that the background conductivity is in control
following the guidance in Section 11.3.2. If the background conductivity is normal,
remedial action may necessary (Sect. 10.4.3).

10.4.2 Calculate the concentration of each analyte in the CCC. The CCC fortified at ≤MRL
must calculate to be within +50% of its true value. CCCs fortified at all other levels must
calculate to be within +30%. If these limits are exceeded, then all data for the failed
analytes must be considered invalid. Any field samples analyzed since the last acceptable
CCC that are still within holding time must be reanalyzed after an acceptable calibration
has been restored.

10.4.3 REMEDIAL ACTION – Failure to meet CCC QC performance criteria requires remedial
action. Acceptable method performance may be restored simply by flushing the column
at the highest eluent concentration in the gradient. Following this and other minor
remedial action, check the calibration with a mid-level CCC and a CCC at the MRL, or
alternatively recalibrate according to Section 10.3. If internal standard and calibration
failures persist, maintenance may be required, such as servicing the ESI-MS/MS system
and replacing IC columns. These later measures constitute major maintenance, and the
analyst must return to the initial calibration step (Sect. 10.3) and verify sensitivity by
analyzing a CCC at or below the MRL.

11. PROCEDURE

11.1 This section describes the procedures for sample preparation and analysis. Important aspects
of this analytical procedure include proper sample collection and storage (Sect. 8), ensuring
that the instrument is properly calibrated (Sect. 10), and that all required QC elements are
included (Sect. 9).

11.2 SAMPLE PREPARATION

11.2.1 All field and QC samples must contain the preservative listed in Section 8.1.2, including
the LRB. In the laboratory, maintain field samples, QC samples, and calibration

557-26
 standards at or below 6 °C at all times, including the time these are resident in the
autosampler awaiting injection.

11.2.2 Do not filter the samples. Add an appropriate volume of the Internal Standard PDS (Sect.
7.3.1.2) to a known volume of sample, cap, and mix well. The concentration of the
internal standards must be the same in the samples as in the calibration standards.
Transfer an aliquot of each field or QC sample to an autosampler vial. For example,
weigh 40 mL of sample into a 40-mL VOA vial using a top loading balance and a
disposable, glass pipette. Add 160 uL of the internal standard PDS (1.0 µg/mL) to
achieve a concentration of 4.0 µg/L in the sample. Mix well and transfer 1.5 mL to an
autosampler vial by use a disposable pipette.

11.3 SAMPLE ANALYSIS

11.3.1 Establish IC-ESI-MS/MS operating conditions per the guidance in Section 10.2.

11.3.2 Flush the column at the highest eluent concentration in the gradient for at least 15
minutes prior to beginning each analysis sequence. This step is especially important for
minimizing background conductivity if the column has been installed in the system and
held at the starting eluent concentration for extended periods.

NOTE: During method development, the background conductivity ranged from 0.3 to
2.2 microsiemens (µS). If an internal standard or analyte area response is low due to high
background conductivity, flush the column at the maximum eluent concentration in the
gradient and observe the conductivity signal until the background stabilizes at less than
2.5 µS. Also, ensure that the suppressor is functioning properly or replace the suppressor
to troubleshoot the problem. Occasional overnight flushing of the column will minimize
the occurrence of high background conductivity.

11.3.3 VERIFY ELUTION AND DIVERT WINDOWS - Analyze Laboratory Synthetic Sample
Matrix fortified at 10 µg/L. Verify the elution and divert windows as specified in Section
10.2.5. This verification must be done prior to beginning each Analysis Batch.

11.3.4 THE ANALYSIS BATCH – Establish a valid initial calibration following the procedures
outlined in Section 10.3 and confirm that the calibration is valid by analyzing a CCC at or
below the MRL as described in Section 10.4. Alternately, verify that an existing
calibration, established for a previous Analysis Batch, is still valid by analyzing a CCC at
or below the MRL. Next, analyze an LRB. Continue the Analysis Batch by analyzing
aliquots of field and QC samples at appropriate frequencies (Section 9.3), employing the
optimized conditions used to acquire the initial calibration. Analyze a mid- or high-level
CCC after every ten field samples and at the end each Analysis Batch.

NOTE: Each Analysis Batch must begin with the analysis of a CCC at or below the
MRL for each analyte that the laboratory intends to report, followed by the analysis of an
LRB. This is true whether or not an initial calibration is analyzed. After 20 field samples
the low-level CCC and the LRB must be repeated to begin a new Analysis Batch. The

557-27
 acquisition start time of the mid-level CCC at the end of the Analysis Batch must be
within 30 hours of the acquisition start time of the low-level CCC at the beginning of the
Analysis Batch. Do not count QC samples (LRBs, LDs, LFSMs, LFSMDs) when
calculating the frequency of CCCs that are required during an Analysis Batch.

12. DATA ANALYSIS AND CALCULATIONS

12.1 Establish an appropriate retention time window for each analyte to identify them in QC and
field sample chromatograms. Base this assignment on measurements of actual retention time
variation for each compound in standard solutions over the course of time. The suggested
variation is plus or minus three times the standard deviation of the retention time for each
compound for a series of injections. The injections from the initial calibration and from the
IDC (Sect. 9.2) may be used to calculate the retention time window. However, the
experience of the analyst should weigh heavily on the determination of an appropriate range.

12.2 At the conclusion of data acquisition, use the same software settings established during the
calibration procedure to identify peaks of interest in the predetermined retention time
windows. Confirm the identify of each analyte by comparison of its retention time with that
of the corresponding analyte peak in an initial calibration standard or CCC.

12.3 Calculate analyte concentrations using the multipoint calibration established in Section 10.3.
Report only those values that fall between the MRL and the highest calibration standard.
Samples with analyte responses that exceed the highest calibration standard require dilution
and reanalysis (Sect. 12.7).

NOTE: In validating this method, concentrations were calculated using the product ions
listed in Table 3 of Section 17. Other ions may be selected at the discretion of the analyst as
discussed in Section 10.2.2.

12.4 Calculations must use all available digits of precision, but final reported concentrations
should be rounded to an appropriate number of significant figures (one digit of uncertainty),
typically two, and not more than three significant figures.

12.5 Prior to reporting the data, the chromatograms must be reviewed for any incorrect peak
identifications or improper integration.

12.6 Prior to reporting data, the laboratory is responsible for ensuring that QC requirements have
been met and that any appropriate qualifier is assigned.

12.7 EXCEEDING THE CALIBRATION RANGE – The analyst must not extrapolate beyond the
established calibration range. If an analyte result exceeds the range of the initial calibration
curve, the sample may be diluted using reagent water containing 100 mg/L NH4Cl with the
appropriate amount of internal standard added to match the original level. Re-inject the
diluted sample. Incorporate the dilution factor into final concentration calculations. The
resulting data must be annotated as a dilution, and the reported MRLs must reflect the
dilution factor.

557-28
13. METHOD PERFORMANCE

13.1 PRECISION, ACCURACY, AND DETECTION LIMITS – The method performance data
presented in Section 17 were collected using the IC conditions listed in Table 1 and the
Waters Quattro Premier XE ESI-MS/MS system. ESI-MS/MS conditions for the Waters
system are presented in Table 2. Tables 3 and 4 list the mass transitions for each analyte and
internal standard, internal standard assignments, and observed retention times associated with
the method performance results. LCMRLs and DLs are presented in Tables 5 and 6. Single
laboratory precision and accuracy data are presented for four water matrices: reagent water
(Table 7), LSSM (Table 8), chlorinated (finished) ground water (Table 9), and chlorinated
(finished) surface water (Table 10). Figure 1 depicts the post-column sample path as
previously cited in this document (Sect. 6.12). Figures 2 through 4 are chromatograms of the
method analytes in reagent water, drinking water, and LSSM obtained under the conditions
employed during method development. Figure 4 was acquired with the inclusion of mass
transitions for the chlorite and chlorate anions to mark their position in the chromatogram
relative to the method analytes. Figure 5 is a corresponding conductivity trace for the analyte
chromatogram presented in Figure 4 showing the location of matrix anions, chlorite anion,
and chlorate anion.

13.2 SECOND LABORATORY EVALUATION – The performance of this method was

demonstrated by a second laboratory using an API 4000 triple quadrupole mass spectrometer
(Applied Biosystems, Foster City, CA) with results similar to those reported in Section 17.
The authors wish to acknowledge the Southern Nevada Water Authority (Las Vegas, NV) for
their contribution to the method development effort.

14. POLLUTION PREVENTION

14.1 For information about pollution prevention that may be applicable to laboratory operations,
consult “Less is Better: Laboratory Chemical Management for Waste Reduction” available
from the American Chemical Society’s Department of Government Relations and Science
Policy, 1155 16th Street N.W., Washington, D.C., 20036, or online at
http://www.ups.edu/x7432.xml.

15. WASTE MANAGEMENT

15.1 The analytical procedures described in this method generate relatively small amounts of
waste since only small amounts of reagents and solvents are used. The matrix of concern is
finished drinking water. However, the Agency requires that laboratory waste management
practices be conducted consistent with all applicable rules and regulations, and that
laboratories protect the air, water, and land by minimizing and controlling all releases from
fume hoods and bench operations. In addition, compliance is required with any sewage
discharge permits and regulations, particularly the hazardous waste identification rules and
land disposal restrictions. For further information on waste management, see the
publications of the American Chemical Society’s Laboratory Environment, Health & Safety
Task Force on the Internet at http://membership.acs.org/c/ccs/publications.htm. Additional

557-29
 waste management information can be found in “Laboratory Waste Minimization and
Pollution Prevention,” Copyright © 1996 Battelle Seattle Research Center, which can be
located at http://www.p2pays.org/ref/01/text/00779/ch05.htm.

16. REFERENCES

1. Winslow, S. D.; Pepich, B. V.; Martin, J. J.; Hallberg, G. R.; Munch D. J.; Frebis, C. P.; Hedrick, E.
J.; Krop, R. A. Statistical Procedures for Determination and Verification of Minimum Reporting
Levels for Drinking Water Methods. Environ. Sci. Technol. 2006; 40, 281-288.

2. Glaser, J.A.; Foerst, D.L.; McKee, G.D.; Quave, S.A.; Budde, W.L. Trace Analyses for
Wastewaters. Environ. Sci. Technol. 1981; 15, 1426-1435.

3. Occupational Exposures to Hazardous Chemicals in Laboratories; 29 CFR 1910.1450, Occupational

Safety and Health Administration, 1990.

4. Safety in Academic Chemistry Laboratories; American Chemical Society Publication, Committee on

Chemical Safety, 7th Edition: Washington, D.C., 2003.

5. Determination of Haloacetic Acids and Dalapon in Drinking Water by Liquid-Liquid

Microextraction, Derivatization, and Gas Chromatography with Electron Capture Detection; U.S.
EPA Method 552.3, EPA 815-B-03-002.

6. Standard Practice for Sampling Water from Closed Conduits; ASTM Annual Book of Standards,
Section 11, Volume 11.01, D3370-08; American Society for Testing and Materials: Philadelphia,
PA, 2008.

7. Application Note 217, Dionex Corp., Sunnyvale, CA.

557-30
17. TABLES, DIAGRAMS, FLOWCHARTS, AND VALIDATION DATA

TABLE 1. ION CHROMATOGRAPHIC CONDITIONS USED TO COLLECT METHOD

PERFORMANCE DATA
Parameter Conditionsa
Column Dionex IonPac® AS24 250 mm x 2 mm i.d.
Precolumn Dionex IonPac® AG24 50 mm x 2 mm i.d.
Column compartment Autosampler tray
15 ºC 4 ºC
temperature temperature
7 mM for -1 to16.8 min, then 18 mM for 16.8 to 34.2 min, then 60 mM
Hydroxide gradient
for 34.4 to 51.2 min, then 7 mM for 51.4 to 56 min
Eluent flow rate 0.30 mL/min
Post-column solvent 100% acetonitrile at 0.2 mL/min
Suppressor Dionex ASRS®300 2 mm, external water mode
Matrix diversion divert
0 to 8 min, 16.5 to 21.2 min, and 33 to 39.2 min
windows
Sample volume 100-µL loop
a
The chromatograms presented in Figures 2, 3, 4, and 5 were obtained under these conditions.

TABLE 2. WATERS QUATTRO PREMIER XE ACQUISITION CONDITIONS USED

TO COLLECT METHOD PERFORMANCE DATAa
Transition Dwell Cone Collision
Analyte (m/z) (seconds) Periods (V) Energy (V)
ISb: Monochloroacetic acid-2-13C 94/35 0.4 -15 -8
Monochloroacetic acid 93/35 1.2 -15 -8
MRM
IS: Monobromoacetic acid-1-13C 138/79 0.4 -15 -10
Window 1
Monobromoacetic acid 137/79 0.4 -15 -10
Bromate 127/111 0.4 -25 -18
Dalapon 141/97 0.5 -18 -8
IS: Dichloroacetic acid-2-13C 128/84 0.5 -17 -10
MRM
Dichloroacetic acid 127/83 0.5 -17 -10
Window 2
Bromochloroacetic acid 173/129 0.5 -17 -10
Dibromoacetic acid 217/173 0.5 -18 -12
IS: Trichloroacetic acid-2-13C 162/118 0.5 -16 -8
161/117
Trichloroacetic acid 0.5 -16 -8
163/119 MRM
Bromodichloroacetic acid 163/81 1.0 Window 3 -25 -10
Chlorodibromoacetic acid 207/79 1.0 -28 -10
Tribromoacetic acid 251/79 1.0 -28 -12
a
Source block: 120 °C, desolvation gas: 350 °C @ 940 liters/hour, capillary: -2.8 V, collision pressure: 5.5x10-3
torr (0.15 flow @ 7 psig), cone flow: 100 liters/hour, extractor: -3 V, RF lens: -0.5 V, acetonitrile flow rate: 0.2
mL/min.
b
IS = internal standard.

557-31
TABLE 3. IC-ESI-MS/MS ANALYTE RETENTION TIMES, PRECURSOR AND PRODUCT
IONS
Retention Timea Internal Standard
Analyte (min) Assignment Precursor Product
Monochloroacetic acid 12.62 MCAA[2-13C] 93 35
Monobromoacetic acid 14.05 MBAA[1-13C] 137 79
Bromate 14.93 MBAA[1-13C] 127 111
Dalapon 23.33 DCAA[2-13C] 141 97
Dichloroacetic acid 24.26 DCAA[2-13C] 127 83
Bromochloroacetic acid 26.16 DCAA[2-13C] 173 129
Dibromoacetic acid 28.89 DCAA[2-13C] 217 173
Trichloroacetic acid TCAA[2-13C] 161 117
41.08
Trichloroacetic acid (alternate) TCAA[2-13C] 163 119
Bromodichloroacetic acid 42.89 TCAA[2-13C] 163 81
Chlorodibromoacetic acid 45.50 TCAA[2-13C] 207 79
Tribromoacetic acid 49.22 TCAA[2-13C] 251 79
a
Dionex AS24 column (used to collect method performance data).

TABLE 4. IC-ESI-MS/MS INTERNAL STANDARD RETENTION TIMES,

PRECURSOR AND PRODUCT IONS
a
Retention Time
,nternal 6tandard (minutes) Precursor Product
Monochloroacetic acid-2-13C 12.56 94 35
Monobromoacetic acid-1-13C 14.05 138 79
Dichloroacetic acid-2-13C 24.21 128 84
Trichloroacetic acid-2-13C 41.08 162 118
a
Dionex AS24 column (used to collect method performance data).

557-32
TABLE 5. IC-ESI-MS/MS LOWEST CONCENTRATION MINIMUM REPORTING LEVEL
(LCMRL)
Calculated LCMRL
Analyte LCMRL Fortification Levels (µg/L) (µg/L)
Monochloroacetic acid 0.10, 0.25, 0.375, 0.50, 0.75, 1.0, 1.25, 1.5, 1.75, 2.0 0.58
0.050, 0.10, 0.25, 0.375, 0.50, 0.75, 1.0, 1.25, 1.5, 1.75,
Monobromoacetic acid 0.19
2.0
0.025, 0.050, 0.10, 0.25, 0.375, 0.50, 0.75, 1.0, 1.25, 1.5,
Bromate 0.042
1.75, 2.0
Dalapon 0.25, 0.375, 0.50, 0.75, 1.0, 1.25, 1.5, 1.75, 2.0 0.41
0.025, 0.050, 0.10, 0.25, 0.375, 0.50, 0.75, 1.0, 1.25, 1.5,
Dichloroacetic acid 0.13
1.75, 2.0
Bromochloroacetic acid 0.10, 0.25, 0.375, 0.50, 0.75, 1.0, 1.25, 1.5, 1.75, 2.0 0.16
0.025, 0.050, 0.10, 0.25, 0.375, 0.50, 0.75, 1.0, 1.25, 1.5,
Dibromoacetic acid 0.062
1.75, 2.0
Trichloroacetic acid – m/z 163/119 0.10, 0.25, 0.375, 0.50, 0.75, 1.0, 1.25, 1.5, 1.75, 2.0 0.25
0.050, 0.10, 0.25, 0.375, 0.50, 0.75, 1.0, 1.25, 1.5, 1.75,
Bromodichloroacetic acid 0.19
2.0
0.050, 0.10, 0.25, 0.375, 0.50, 0.75, 1.0, 1.25, 1.5, 1.75,
Chlorodibromoacetic acid 0.080
2.0
Tribromoacetic acid 0.10, 0.25, 0.375, 0.50, 0.75, 1.0, 1.25, 1.5, 1.75, 2.0 0.27

TABLE 6. IC-ESI-MS/MS DETECTION LIMITS (DL)a

Analyte Fortification Level (µg/L) Calculated DL (µg/L)
Monochloroacetic acid 0.25 0.20
Monobromoacetic acid 0.10 0.064
Bromate 0.025 0.020
Dalapon 0.25 0.038
Dichloroacetic acid 0.10 0.055
Bromochloroacetic acid 0.25 0.11
Dibromoacetic acid 0.025 0.015
Trichloroacetic acid – m/z 163/119 0.10 0.090
Bromodichloroacetic acid 0.050 0.050
Chlorodibromoacetic acid 0.10 0.041
Tribromoacetic acid 0.25 0.067
a
DLs calculated using data acquired over the course of three days (n=7 sample replicates).

557-33
TABLE 7. IC-ESI-MS/MS PRECISION AND ACCURACY OF METHOD ANALYTES
FORTIFIED AT 1.0 AND 15 µg/L IN REAGENT WATER
Fortified Conc. = 1.0 µg/L Fortified Conc. = 15 µg/L
(n=7) (n=8)
Mean % Relative Standard Mean % Relative Standard
Analyte Recovery Deviation Recovery Deviation
Monochloroacetic acid 101 3.5 101 1.7
Monobromoacetic acid 97.5 3.7 99.8 1.8
Bromate 93.3 2.4 104 7.8
Dalapon 97.4 4.7 100 3.3
Dichloroacetic acid 109 2.6 97.0 6.5
Bromochloroacetic acid 103 2.9 107 4.4
Dibromoacetic acid 104 9.0 111 6.7
Trichloroacetic acid – m/z 163/119 99.1 2.3 99.8 3.2
Bromodichloroacetic acid 105 3.7 97.7 2.2
Chlorodibromoacetic acid 90.4 5.9 103 5.4
Tribromoacetic acid 101 5.3 98.9 3.0

TABLE 8. IC-ESI-MS/MS PRECISION AND ACCURACY OF METHOD ANALYTES

FORTIFIED AT 1.0 AND 15 µg/L IN SYNTHETIC SAMPLE MATRIX
Fortified Conc. = 1.0 µg/L Fortified Conc. = 15 µg/L
(n=8) (n=8)
Mean % Relative Standard Mean % Relative Standard
Analyte Recovery Deviation Recovery Deviation
Monochloroacetic acid 109 4.8 101 4.1
Monobromoacetic acid 97.2 5.3 99.7 4.6
Bromate 117 11 109 11
Dalapon 113 4.5 93.2 6.6
Dichloroacetic acid 89.9 9.3 90.9 8.7
Bromochloroacetic acid 84.9 9.3 82.8 10
Dibromoacetic acid 91.0 14 84.5 10
Trichloroacetic acid – m/z 163/119 107 5.4 101 1.1
Bromodichloroacetic acid 91.6 4.7 91.0 4.1
Chlorodibromoacetic acid 98.8 7.2 97.6 6.2
Tribromoacetic acid 94.0 5.4 97.6 2.5

557-34
TABLE 9. IC-ESI-MS/MS PRECISION AND ACCURACY OF METHOD ANALYTES
FORTIFIED AT 2.5 AND 10 µg/L IN CHLORINATED GROUND WATERa
Native Fortified Conc. = 2.5 µg/L Fortified Conc. = 10 µg/L
Conc., (n=8) (n=8)
μg/L Mean % Relative Standard Mean % Relative Standard
Analyte (n=6) Recoveryb Deviation Recoveryb Deviation
Monochloroacetic acid 0.57 95.9 4.7 99.6 5.2
Monobromoacetic acid 0.41 101 2.1 101 1.8
Bromate 0.56 107 7.3 102 4.8
Dalapon 0.37 95.5 3.1 98.5 3.0
Dichloroacetic acid 4.3 99.7 6.2 106 1.7
Bromochloroacetic acid 3.4 95.2 5.6 93.5 3.1
Dibromoacetic acid 2.0 95.2 8.1 99.3 6.2
Trichloroacetic acid – m/z 163/119 2.6 101 1.8 102 2.8

Bromodichloroacetic acid 2.6 91.2 2.0 99.0 3.6

Chlorodibromoacetic acid 1.7 103 3.6 102 7.2

Tribromoacetic acid 0.24 97.6 1.9 95.8 1.9
a
Ground water physical parameters: pH = 7.45; total hardness = 308 milligrams/liter (mg/L) (as CaCO3); free chlorine =
0.94 mg/L.
b
Recoveries corrected for native levels in the unfortified matrix.

TABLE 10. IC-ESI-MS/MS PRECISION AND ACCURACY OF METHOD ANALYTES

FORTIFIED AT 2.5 AND 8.0 µg/L IN CHLORINATED SURFACE WATERa
Native Fortified Conc. = 2.5 µg/L Fortified Conc. = 8.0 µg/L
Conc., (n=8) (n=7)
μg/L Mean % Relative Standard Mean % Relative Standard
Analyte (n=6) Recoveryb Deviation Recoveryb Deviation
Monochloroacetic acid 2.6 97.9 3.5 98.8 3.0
Monobromoacetic acid 0.66 99.3 1.4 101 1.6
Bromate 0.85 99.0 8.8 103 10
Dalapon 0.72 97.8 3.8 96.3 4.8
Dichloroacetic acid 15 79.6 6.3 80.0 6.0
Bromochloroacetic acid 6.4 87.2 9.0 90.2 9.2
Dibromoacetic acid 1.6 106 10 95.8 6.0
Trichloroacetic acid – m/z 163/119 11 95.6 2.5 97.1 1.4
Bromodichloroacetic acid 4.7 99.9 4.6 97.9 4.9
Chlorodibromoacetic acid 1.2 102 5.9 102 11
Tribromoacetic acid 0.081 99.5 3.9 103 4.7
a
Surface water physical parameters: pH = 7.43; total hardness = 154 milligrams/liter (mg/L) (as CaCO3); free chlorine =
2.7 mg/L; total chlorine = 3.7 mg/L.
b
Recoveries corrected for native levels in the unfortified matrix.

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TABLE 11. INITIAL DEMONSTRATION OF CAPABILITY (IDC) QUALITY CONTROL
REQUIREMENTS
Method
Requirement Specification and Frequency Acceptance Criteria
Reference
Demonstrate that all method analytes
are <1/3 of the Minimum Reporting
Demonstration of Analyze a Laboratory Reagent Level (MRL) and that possible
Section
low system Blank (LRB) prior to any other interferences from reagents and
9.2.1
background Initial IDC steps. glassware do not prevent the
identification and quantitation of
method analytes.
Analyze an LRB after the high
Section Test for system Demonstrate that the method analytes
calibration standard during the IDC
9.2.1 carryover are <1/3 of the MRL.
calibration.
Analyze 7 replicate Laboratory
Fortified Blanks (LFBs) and 7
Section Demonstration of Laboratory Fortified Synthetic Percent relative standard deviation
9.2.2 precision Sample Matrix samples (LFSSMs) must be ≤20%.
fortified near the midrange
concentration.
Section Demonstration of Calculate average recovery for Mean recovery within +30% of the true
9.2.3 accuracy replicates used in Section 9.2.2. value.
Fortify and analyze 7 replicate LFBs
Upper PIR ≤ 150%
at the proposed MRL concentration.
Section MRL Confirm that the Upper Prediction
9.2.4 confirmation Interval of Results (PIR) and Lower Lower PIR ≥ 50%
PIR (Sect. 9.2.4.2) meet the
recovery criteria.
Section Quality Control Results must be within +30% of the
Analyze mid-level QCS.
9.2.5 Sample (QCS) true value.

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TABLE 12. ONGOING QUALITY CONTROL REQUIREMENTS
Method
Requirement Specification and Frequency Acceptance Criteria
Reference
Analyze a Laboratory Fortified
Section Verify divert See Section 10.2.5 for acceptance
Synthetic Sample Matrix (LFSSM)
11.3.3 windows criteria.
prior to each Analysis Batch.
Use the internal standard cali­ When each calibration standard is
bration technique to generate a calculated as an unknown using the
linear or quadratic calibration regression equations, the lowest
Section
Initial calibration curve. Use at least five standard level standard must be within +50%
10.3
concentrations. Validate the cali­ of the true value. All other points
bration curve as described in must be within +30% of the true
Section 10.3.3. value.
Demonstrate that all method ana­
lytes are below 1/3 the Minimum
Reporting Level (MRL), and that
Section Laboratory Reagent Analyze one LRB with each
Analysis Batch.
possible interference from reagents
9.3.1 Blank (LRB)
and glassware do not prevent identi­
fication and quantitation of method
analytes.
The lowest level CCC must be
Verify initial calibration by ana­ within +50% of the true value. All
lyzing a low-level CCC at the other points must be within +30% of
beginning of each Analysis Batch. the true value.
Section Continuing Calibra­
Subsequent CCCs are required
10.4 tion Check (CCC)
after every 10 field samples, and
after the last field sample in a Results for field samples that are not
batch. bracketed by acceptable CCCs are
invalid.
Isotopically labeled internal Peak area counts for each IS must be
Section
Internal standard (IS) standards are added to all standards within ±50% of the average peak
9.3.4
and samples. areas in the initial calibration.
Analyze one LFSM per Analysis For LFSMs fortified at concen­
Batch. Fortify the LFSM with trations <2 x MRL, the result must
Laboratory Fortified
Section method analytes at a concentration be within +50% of the true value.
Sample Matrix
9.3.5 greater than the native At concentrations greater than the 2
(LFSM)
concentrations of most analytes. x MRL, the result must be within
Calculate LFSM recoveries. +30% of the true value.
Laboratory Fortified
Sample Matrix Dup­ For LFSMDs or LDs, relative
Section Analyze at least one LFSMD or
licate (LFSMD) or percent differences must be ≤30%.
9.3.6 LD with each Analysis Batch.
Laboratory Duplicate (≤50% if concentration <2 x MRL.)
(LD)
Section Quality Control Analyze mid-level QCS at least Results must be +30% of the true
9.3.7 Sample (QCS) quarterly. value.

557-37
Figure 1. Divert valve placement in sample path.

557-38
Figure 2. Dionex AS24 column: procedural calibration standard (5 µg/L).

557-39
Figure 3. Dionex AS24 column: tap water fortified at 8 µg/L.

557-40
Figure 4. Dionex AS24 column: synthetic sample matrix fortified at 5 µg/L plus chlorite (1 mg/L) and chlorate (0.5 mg/L).

557-41
Figure 5. Dionex AS24 column: conductivity trace, synthetic sample matrix plus chlorite (1 mg/L) and chlorate (0.5 mg/L).

557-42