METHOD 502.

VOLATILE ORGANIC COMPOUNDS IN WATER BY PURGE AND TRAP

CAPILLARY COLUMN GAS CHROMATOGRAPHY WITH
PHOTOIONIZATION AND ELECTROLYTIC CONDUCTIVITY
DETECTORS IN SERIES

Revision 2.0

R.W. Slater, Jr. and J.S. Ho -- Method 502.2, Revision 1.0 (1986)

J.S. Ho -- Method 502.2, Revision 2.0 (1989)

ENVIRONMENTAL MONITORING SYSTEMS LABORATORY

OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268

502.2-1
 METHOD 502.2

VOLATILE ORGANIC COMPOUNDS IN WATER BY PURGE AND TRAP

CAPILLARY COLUMN GAS CHROMATOGRAPHY WITH
PHOTOIONIZATION AND ELECTROLYTIC CONDUCTIVITY
DETECTORS IN SERIES

1.0 SCOPE AND APPLICATION

1.1 This is a general purpose method for the identification and simultaneous
measurement of purgeable volatile organic compounds in finished drinking water,
raw source water, or drinking water in any treatment stage 1-3. The method is
applicable to a wide range of organic compounds, including the four
trihalomethane disinfection by-products, that have sufficiently high volatility and
low water solubility to be efficiently removed from water samples with purge and
trap procedures. The following compounds can be determined by this method.

Chemical Abstract Services

Analyte Registry Number
Benzene 71-43-2
Bromobenzene 108-86-1
Bromochloromethane 74-97-5
Bromodichloromethane 75-27-4
Bromoform 75-25-2
Bromomethane 74-83-9
n-Butylbenzene 104-51-8
sec-Butylbenzene 135-98-8
tert-Butylbenzene 98-06-6
Carbon tetrachloride 56-23-5
Chlorobenzene 108-90-7
Chloroethane 75-00-3
Chloroform 67-66-3
Chloromethane 74-87-3
2-Chlorotoluene 95-49-8
4-Chlorotoluene 106-43-4
Dibromochloromethane 124-48-1
1,2-Dibromo-3-chloropropane 96-12-8
1,2-Dibromoethane 106-93-4
Dibromomethane 74-95-3
1,2-Dichlorobenzene 95-50-1
1,3-Dichlorobenzene 541-73-1
1,4-Dichlorobenzene 106-46-7
Dichlorodifluoromethane 75-71-8
1,1-Dichloroethane 75-34-3
1,2-Dichloroethane 107-06-2

502.2-2
 Chemical Abstract Services
Analyte Registry Number
1,1-Dichloroethene 75-35-4
cis-1,2-Dichloroethene 156-59-4
trans-1,2-Dichloroethene 156-60-5
1,2-Dichloropropane 78-87-5
1,3-Dichloropropane 142-28-9
2,2-Dichloropropane 590-20-7
1,1-Dichloropropene 563-58-6
cis-1,3-Dichloropropene 10061-01-5
trans-1,3-Dichloropropene 10061-02-6
Ethylbenzene 100-41-4
Hexachlorobutadiene 87-68-3
Isopropylbenzene 98-82-8
4-Isopropyltoluene 99-87-6
Methylene chloride 75-09-2
Naphthalene 91-20-3
Propylbenzene 103-65-1
Styrene 100-42-5
1,1,1,2-Tetrachloroethane 630-20-6
1,1,2,2-Tetrachloroethane 79-34-5
Tetrachloroethene 127-18-4
Toluene 108-88-3
1,2,3-Trichlorobenzene 87-61-6
1,2,4-Trichlorobenzene 120-82-1
1,1,1-Trichloroethane 71-55-6
1,1,2-Trichloroethane 79-00-5
Trichloroethene 79-01-6
Trichlorofluoromethane 75-69-4
1,2,3-Trichloropropane 96-18-4
1,2,4-Trimethylbenzene 95-63-6
1,3,5-Trimethylbenzene 108-67-8
Vinyl chloride 75-01-4
o-Xylene 95-47-6
m-Xylene 108-38-3
p-Xylene 106-42-3

1.2 This method is applicable to the determination of total trihalomethanes and other
volatile synthetic compounds as required by drinking water regulations of 40
Code of Federal Regulations Part 141. Method detection limits (MDLs)4 are
compound and instrument dependent and vary from approximately 0.01-3.0
µg/L. The applicable concentration range of this method is also compound and
instrument dependent and is approximately 0.02-200 µg/L. Analytes that are
inefficiently purged from water will not be detected when present at low
concentrations, but they can be measured with acceptable accuracy and precision
when present in sufficient amounts.

502.2-3
 1.3 Two of the three isomeric xylenes may not be resolved on the capillary column,
and if not, must be reported as isomeric pairs.

2.0 SUMMARY OF METHOD

2.1 Highly volatile organic compounds with low water solubility are extracted
(purged) from the sample matrix by bubbling an inert gas through a 5 mL
aqueous sample. Purged sample components are trapped in a tube containing
suitable sorbent materials. When purging is complete, the sorbent tube is heated
and backflushed with helium to desorb trapped sample components onto a
capillary gas chromatography (GC) column. The column is temperature
programmed to separate the method analytes which are then detected with a
photoionization detector (PID) and a halogen specific detector placed in series.

2.2 Tentative identifications are confirmed by analyzing standards under the same
conditions used for samples and comparing resultant GC retention times.
Additional confirmatory information can be gained by comparing the relative
response from the two detectors. Each identified component is measured by
relating the response produced for that compound to the response produced by
a compound that is used as an internal standard. For absolute confirmation, a gas
chromatography/mass spectrometry(GC/MS) determination according to Method
524.1 or Method 524.2 is recommended.

3.0 DEFINITIONS

3.1 Internal Standard -- A pure analyte(s) added to a solution in known amount(s)

and used to measure the relative responses of other method analytes and
surrogates that are components of the same solution. The internal standard must
be an analyte that is not a sample component.

3.2 Surrogate Analyte -- A pure analyte(s), which is extremely unlikely to be found

in any sample, and which is added to a sample aliquot in known amount(s)
before extraction and is measured with the same procedures used to measure
other sample components. The purpose of a surrogate analyte is to monitor
method performance with each sample.

3.3 Laboratory Duplicates (LD1 and LD2) -- Two sample aliquots taken in the
analytical laboratory and analyzed separately with identical procedures. Analyses
of LD1 and LD2 give a measure of the precision associated with laboratory
procedures, but not with sample collection, preservation, or storage procedures.

3.4 Field Duplicates (FD1 and FD2) -- Two separate samples collected at the same
time and place under identical circumstances and treated exactly the same
throughout field and laboratory procedures. Analyses of FD1 and FD2 give a
measure of the precision associated with sample collection, preservation and
storage, as well as with laboratory procedures.

502.2-4
3.5 Laboratory Reagent Blank (LRB) -- An aliquot of reagent water that is treated
exactly as a sample including exposure to all glassware, equipment, solvents,
reagents, internal standards, and surrogates that are used with other samples.
The LRB is used to determine if method analytes or other interferences are
present in the laboratory environment, the reagents, or the apparatus.

3.6 Field Reagent Blank (FRB) -- Reagent water placed in a sample container in the
laboratory and treated as a sample in all respects, including exposure to sampling
site conditions, storage, preservation and all analytical procedures. The purpose
of the FRB is to determine if method analytes or other interferences are present
in the field environment.

3.7 Laboratory Performance Check Solution (LPC) -- A solution of method analytes,

surrogate compounds, and internal standards used to evaluate the performance
of the instrument system with respect to a defined set of method criteria.

3.8 Laboratory Fortified Blank (LFB) -- An aliquot of reagent water to which known
quantities of the method analytes are added in the laboratory. The LFB is
analyzed exactly like a sample, and its purpose is to determine whether the
methodology is in control, and whether the laboratory is capable of making
accurate and precise measurements at the required method detection limit.

3.9 Laboratory Fortified Sample Matrix (LFM) -- An aliquot of an environmental

sample to which known quantities of the method analytes are added in the
laboratory. The LFM is analyzed exactly like a sample, and its purpose is to
determine whether the sample matrix contributes bias to the analytical results.
The background concentrations of the analytes in the sample matrix must be
determined in a separate aliquot and the measured values in the LFM corrected
for background concentrations.

3.10 Stock Standard Solution -- A concentrated solution containing a single certified

standard that is a method analyte, or a concentrated solution of a single analyte
prepared in the laboratory with an assayed reference compound. Stock standard
solutions are used to prepare primary dilution standards.

3.11 Primary Dilution Standard Solution -- A solution of several analytes prepared in

the laboratory from stock standard solutions and diluted as needed to prepare
calibration solutions and other needed analyte solutions.

3.12 Calibration Standard (CAL) -- A solution prepared from the primary dilution
standard solution and stock standard solutions of the internal standards and
surrogate analytes. The CAL solutions are used to calibrate the instrument
response with respect to analyte concentration.

3.13 Quality Control Sample (QCS) -- A sample matrix containing method analytes or
a solution of method analytes in a water miscible solvent which is used to fortify
reagent water or environmental samples. The QCS is obtained from a source

502.2-5
 external to the laboratory, and is used to check laboratory performance with
externally prepared test materials.

4.0 INTERFERENCES

4.1 During analysis, major contaminant sources are volatile materials in the
laboratory and impurities in the inert purging gas and in the sorbent trap. The
use of non-polytetrafluoroethylene (PTFE) plastic tubing, non-PTFE thread
sealants, or flow controllers with rubber components in the purging device should
be avoided since such materials out-gas organic compounds which will be
concentrated in the trap during the purge operation. Analyses of laboratory
reagent blanks (Section 10.3) provide information about the presence of
contaminants. When potential interfering peaks are noted in laboratory reagent
blanks, the analyst should change the purge gas source and regenerate the
molecular sieve purge gas filter. Subtracting blank values from sample results is
not permitted.

4.2 Interfering contamination may occur when a sample containing low

concentrations of volatile organic compounds is analyzed immediately after a
sample containing relatively high concentrations of volatile organic compounds.
A preventive technique is between-sample rinsing of the purging apparatus and
sample syringes with two portions of reagent water. After analysis of a sample
containing high concentrations of volatile organic compounds, one or more
laboratory reagent blanks should be analyzed to check for cross contamination.

4.3 Special precautions must be taken to analyze for methylene chloride. The
analytical and sample storage area should be isolated from all atmospheric
sources of methylene chloride, otherwise random background levels will result.
Since methylene chloride will permeate through PTFE tubing, all gas
chromatography carrier gas lines and purge gas plumbing should be constructed
from stainless steel or copper tubing. Laboratory clothing worn by the analyst
should be clean since clothing previously exposed to methylene chloride fumes
during common liquid/liquid extraction procedures can contribute to sample
contamination.

4.4 When traps containing combinations of silica gel and coconut charcoal are used,
residual water from previous analyses collects in the trap and can be randomly
released into the analytical column. To minimize the possibility of this occurring,
the trap is reconditioned after each use as described in Section 11.4.

502.2-6
5.0 SAFETY

5.1 The toxicity or carcinogenicity of chemicals 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 awareness of OSHA regulations regarding safe
handling of chemicals used in this method. Additional references to laboratory
safety are available5-7 for the information of the analyst.

5.2 The following method analytes have been tentatively classified as known or
suspected human or mammalian carcinogens: benzene, carbon tetrachloride,
1,4-dichlorobenzene, 1,2-dichlorethane, hexachlorobutadiene,
1,1,2,2-tetrachloroethane, 1,1,2-trichloroethane, chloroform, 1,2-dibromoethane,
tetrachloroethene, trichloroethene, and vinyl chloride. Pure standard materials
and stock standard solutions of these compounds should be handled in a hood.
A NIOSH/MESA approved toxic gas respirator should be worn when the analyst
handles high concentrations of these toxic compounds.

6.0 APPARATUS AND EQUIPMENT

6.1 Sample Containers -- 40-120 mL screw cap vials each equipped with a PTFE-faced
silicone septum. Prior to use, wash vials and septa with detergent and rinse with
tap and distilled water. Allow the vials and septa to air dry at room temperature,
place in a 105°C oven for one hour, then remove and allow to cool in an area
known to be free of organics.

6.2 Purge and Trap System -- The purge and trap system consists of three separate
pieces of equipment: purging device, trap, and desorber. Systems are
commercially available from several sources that meet all of the following
specifications.

6.2.1 The all glass purging device (Figure 1) must be designed to accept 5 mL
samples with a water column at least 5 cm deep. Gaseous volumes above
the sample must be kept to a minimum (<15 mL) to eliminate dead
volume effects. A glass frit should be installed at the base of the sample
chamber so that the purge gas passes through the water column as finely
divided bubbles with a diameter of <3 mm at the origin. Needle spargers
may be used, however, the purge gas must be introduced at a point <5
mm from the base of the water column.

6.2.2 The trap (Figure 2) must be at least 25 cm long and have an inside
diameter of at least 0.105 in. Starting from the inlet, the trap must contain
the following amounts of adsorbents: a of 2,6-diphenylene oxide
polymer, a of silica gel, and a of coconut charcoal. It is recommended
that 1.0 cm of methyl silicone coated packing be inserted at the inlet to
extend the life of the trap. If it is not necessary to analyze for
dichlorodifluoromethane, the charcoal can be eliminated and the polymer
b
increased to fill of the trap. If only compounds boiling above 35°C are

502.2-7
 to be analyzed, both the silica gel and charcoal can be eliminated and the
polymer increased to fill the entire trap. Before initial use, the trap should
be conditioned overnight at 180°C by backflushing with an inert gas flow
of at least 20 mL/min. Vent the trap effluent to the room, not to the
analytical column. Prior to daily use, the trap should be conditioned for
10 minutes at 180°C with backflushing. The trap may be vented to the
analytical column during daily conditioning; however, the column must
be run through the temperature program prior to analysis of samples.

6.2.3 The use of the methyl silicone coated packing is recommended, but not
mandatory. The packing serves a dual purpose of protecting the
adsorbent from aerosols, and also of insuring that the adsorbent is fully
enclosed within the heated zone of the trap thus eliminating potential cold
spots. Alternatively, silanized glass wool may be used as a spacer at the
trap inlet.

6.2.4 The desorber (Figure 2) must be capable of rapidly heating the trap to
180°C. The polymer section of the trap should not be heated higher than
200°C or the life expectancy of the trap will decrease. Trap failure is
characterized by a pressure drop in excess of 3 pounds per square inch
across the trap during purging or by poor bromoform sensitivities.

6.3 Gas Chromatography System

6.3.1 The GC must be capable of temperature programming and should be

equipped with variable-constant differential flow controllers so that the
column flow rate will remain constant throughout desorption and
temperature program operation. The column oven may need to be cooled
to <10°C (Section 6.3.3), therefore, a subambient oven controller may be
required.

6.3.2 Capillary gas chromatography columns -- Any gas chromatography

column that meets the performance specifications of this method may be
used. Separations of the calibration mixture must be equivalent or better
than those described in this method. Three useful columns have been
identified: Column 1 (Section 6.3.3) and Column 2 (Section 6.3.4) both
provide satisfied separations for sixty organic compounds. Column 3
(Section 6.3.5), which has been demonstrated satisfactory for GC/MS
Method 524.2, may also be used.

6.3.3 Column 1 -- 60 m long x 0.75 mm ID VOCOL (Supelco, Inc.) wide-bore

capillary column with 1.5 µm film thickness, or equivalent. The flow rate
of helium carrier gas is adjusted to about 6 mL/min. The column
temperature is held for eight minutes at 10°C, then programmed to 180°C
at 4°C/min, and held until all expected compounds have eluted. A
sample chromatogram obtained with this column is presented in Figure
3. Retention times that may be anticipated with this column are listed in

502.2-8
 Table 1. It was used to develop the method performance statements in
Section 13.0.

6.3.4 Column 2 -- 105 m long x 0.53 mm ID, RTX-502.2 (O.I

Corporation/RESTEK Corporation) mega-bore capillary column, with 3.0
µm film thickness, or equivalent. The flow rate of helium carrier gas is
adjusted to about 8 mL/min. The column temperature is held for 10
minutes at 35°C, then programmed to 200°C at 4°C/min, and held until
all expected compounds have eluted. A sample chromatogram obtained
with this column is presented in Figure 4. Retention times that may be
anticipated with this column are listed in Table 3. It was used to develop
the method performance statements in Section 13.0.

6.3.5 Column 3 -- 30 m long x 0.53 mm ID DB-62 mega-bore (J&W Scientific,

Inc.) column with 3 µm film thickness.

6.3.6 A series configuration of a high temperature photoionization detector

(PID) equipped with 10.0 eV (nominal) lamp and electroconductivity
detector (ELCD) is required. This allows to simultaneously analyze
volatile organic compounds (VOC) that are aromatic or unsaturated by
photoionization detector and organohalide by an electrolytic conductivity
detector.

6.3.7 A Tracor 703 photoionization detector and a Tracor Hall Model 700-A
detector connected in series with a short piece of uncoated capillary tube,
0.32 mm ID was used to develop the single laboratory method
performance data described in Section 13.0. The system and operating
conditions used to collect these data are as follows:

Column: Column 1 (Section 6.3.3)

The purge-and-trap Unit: Tekmar LSC-2
PID detector base temperature: 250°C
Reactor tube: Nickel 1/16 in. OD
Reactor temperature: 810°C
Reactor base temperature: 250°C
Electrolyte: 100% n-propyl alcohol
Electrolyte flow rate: 0.8 mL/min.
Reaction gas: Hydrogen at 40 mL/min.
Carrier gas plus make-up gas: Helium at 30 mL/min.

6.3.8 An O.I. Model 4430 photoionization detector mounting together with the
model 4420 electrolytic conductivity detector (ELCD) as a dual detector set
was used to develop the single laboratory method performance data for
Column 2 described in Section 13.0. The system and the operating
conditions used to collect these data are as follows:

502.2-9
 Column: Column 2 (Section 6.3.4)
The purge-and-trap unit: O.I. 4460A
Reactor tube: Nickel 1/16 in. OD & .02in.ID
Reactor temperature: 950°C
Reactor base temperature: 250°C
Electrolyte: 100 % n-propyl alcohol
Electrolyte flow rate: 0.050 mL/min.
Reaction gas: Hydrogen at 100 mL/min.
Carrier gas plus make-up gas: Helium at 30 mL/min.

6.4 Syringe and Syringe Valves

6.4.1 Two 5 mL glass hypodermic syringes with Luer-Lok tip.

6.4.2 Three two-way syringe valves with Luer ends.

6.4.3 One 25 µL micro syringe with a 2 in x 0.006 in ID, 22° bevel needle
(Hamilton #702N or equivalent).

6.4.4 Micro syringes -- 10, 100 µL.

6.4.5 Syringes -- 0.5, 1.0, and 5 mL, gas tight with shut-off valve.

6.5 Miscellaneous

6.5.1 Standard solution storage containers -- 15 mL bottles with PTFE-lined

screw caps.

7.0 REAGENT AND CONSUMABLE MATERIALS

7.1 Trap Packing Materials

7.1.1 2,6-Diphenylene oxide polymer -- 60/80 mesh, chromatographic grade

(Tenax GC or equivalent).

7.1.2 Methyl silicone packing (optional) -- OV-1 (3%) on Chromosorb-W, 60/80

mesh or equivalent.

7.1.3 Silica gel -- 35/60 mesh, Davison, grade 15 or equivalent.

7.1.4 Coconut charcoal -- Prepare from Barnebey Cheney, CA-580-26

lot #M-2649 by crushing through 26-mesh screen.

7.2 Reagents

7.2.1 Ascorbic acid -- ACS reagent grade, granular.

7.2.2 Sodium thiosulfate -- ACS reagent grade, granular.

502.2-10
 7.2.3 Hydrochloric acid (1+1) -- Carefully add a measured volume of conc. HCl
to equal volume of reagent water.

7.2.4 Reagent water -- It should be demonstrated to be free of analytes. Prepare

reagent water by passing tap water through a filter bed containing about
0.5 kg of activated carbon, by using a water purification system, or by
boiling distilled water for 15 minutes followed by a one-hour purge with
inert gas while the water temperature is held at 90°C. Store in clean,
narrow-mouth bottles with PTFE-lined septa and screw caps.

7.2.5 Methanol -- demonstrated to be free of analytes.

7.2.6 Vinyl chloride -- 99.9% pure vinyl chloride is available from Ideal Gas
Products, Inc., Edison, New Jersey and from Matheson, East Rutherford,
New Jersey. Certified mixtures of vinyl chloride in nitrogen at 1.0 and
10.0 ppm (v/v) are available from several sources.

7.3 Stock Standard Solutions -- These solutions may be purchased as certified

solutions or prepared from pure standard materials using the following
procedures:

7.3.1 Place about 9.8 mL of methanol into a 10 mL ground-glass stoppered

volumetric flask. Allow the flask to stand, unstoppered, for about
10 minutes or until all alcohol-wetted surfaces have dried. Weigh to the
nearest 0.1 mg.

7.3.2 If the analyte is a liquid at room temperature, use a 100 µL syringe and
immediately add two or more drops of reference standard to the flask. Be
sure that the reference standard falls directly into the alcohol without
contacting the neck of the flask. If the analyte is a gas at room
temperature, fill a 5 mL valved gas-tight syringe with the standard to the
5.0 mL mark, lower the needle to 5 mm above the methanol meniscus, and
slowly inject the standard into the neck area of the flask. The gas will
rapidly dissolve in the methanol.

7.3.3 Reweigh, dilute to volume, stopper, then mix by inverting the flask several
times. Calculate the concentration in micrograms per microliter from the
net gain in weight. When compound purity is certified at 96% or greater,
the weight can be used without correction to calculate the concentration
of the stock standard.

7.3.4 Store stock standard solutions in 15 mL bottles equipped with PTFE-lined

screw caps. Methanol solutions prepared from liquid analytes are stable
for at least four weeks when stored at 4°C. Methanol solutions prepared
from gaseous analytes are not stable for more than one week when stored
at <0°C; at room temperature, they must be discarded after one day.
Storage time may be extended only if the analyte proves their validity by
analyzing quality control samples.

502.2-11
 7.4 Primary Dilution Standard Solution -- Use stock standard solutions to prepare
primary dilution standard solutions that contain the analytes in methanol. The
primary dilution standards should be prepared at concentrations that can be
easily diluted to prepare aqueous calibration standard solutions (Section 9.1) that
will bracket the working concentration range. Store the primary dilution standard
solutions with minimal headspace and check frequently for signs of deterioration
or evaporation, especially just before preparing calibration standard solutions
from them. Storage times described for stock standard solutions in Section 7.3.4
also apply to primary dilution standard solutions.

7.5 Internal Standard Solution -- Prepare a fortified solution containing 1-chloro-

2-fluorobenze or fluorobenzene and 2-bromo-1-chloropropane in methanol using
the procedures described in Sections 7.3 and 7.4. It is recommended that the
primary dilution standard be prepared at a concentration of 5 µg/mL of each
internal standard compound. The addition of 10 µL of such a standard to 5.0 mL
of sample or calibration standard would be equivalent to 10 µg/L.

8.0 SAMPLE COLLECTION, PRESERVATION, AND STORAGE

8.1 Sample Collection, Dechlorination, and Preservation

8.1.1 Collect all samples in duplicate. If samples contain residual chlorine, and
measurements of the concentrations of disinfection by-products
(trihalomethanes, etc.) at the time of sample collection are desired, add
about 25 mg of ascorbic acid (or 3 mg of sodium thiosulfate) to the sample
bottle before filling. Fill sample bottles to overflowing, but take care not
to flush out the rapidly dissolving ascorbic acid (or sodium thiosulfate).
No air bubbles should pass through the sample as the bottle is filled, or
be trapped in the sample when the bottle is sealed. Adjust the pH of the
duplicate samples to <2 by carefully adding one drop of 1:1 HCl for each
20 mL of sample volume. Seal the sample bottles, PFTE-face down, and
shake vigorously for one minute.

8.1.2 When sampling from a water tap, open the tap and allow the system to
flush until the water temperature has stabilized (usually about
10 minutes). Adjust the flow to about 500 mL/min and collect duplicate
samples from the flowing stream.

8.1.3 When sampling from an open body of water, fill a 1 qt wide-mouth bottle
or 1 L beaker with sample from a representative area, and carefully fill
duplicate sample bottles from the 1 qt container.

8.1.4 The samples must be chilled to 4°C on the day of collection and
maintained at that temperature until analysis. Field samples that will not
be received at the laboratory on the day of collection must be packaged
for shipment with sufficient ice to ensure that they will be at 4°C on
arrival at the laboratory.

502.2-12
 8.2 Sample Storage

8.2.1 Store samples at 4°C until analysis. The sample storage area must be free
of organic solvent vapors.

8.2.2 Analyze all samples within 14 days of collection. Samples not analyzed
within this period must be discarded and replaced.

8.3 Field Reagent Blanks

8.3.1 Duplicate field reagent blanks must be handled along with each sample
set, which is composed of the samples collected from the same general
sample site at approximately the same time. At the laboratory, fill field
blank sample bottles with reagent water, seal, and ship to the sampling
site along with empty sample bottles and back to the laboratory with filled
sample bottles. Wherever a set of samples is shipped and stored, it is
accompanied by appropriate blanks.

8.3.2 Use the same procedures used for samples to add ascorbic acid (or sodium
thiosulfate) and HCl to blanks (Section 8.1.1).

9.0 CALIBRATION AND STANDARDIZATION

9.1 Preparation of Calibration Standards

9.1.1 The number of calibration solutions (CALs) needed depends on the

calibration range desired. A minimum of three CAL solutions is required
to calibrate a range of a factor of 20 in concentration. For a factor of 50
use at least four standards, and for a factor of 100 at least five standards.
One calibration standard should contain each analyte of concern at a
concentration 2-10 times greater than the method detection limit (Tables
2 and 4) for that compound. The other CAL standards should contain
each analyte of concern at concentrations that define the range of the
sample analyte concentrations. Every CAL solution contains the internal
standard at same concentration (10 µg/L).

9.1.2 To prepare a calibration standard, add an appropriate volume of a

primary dilution standard solution to an aliquot of reagent water in a
volumetric container or sample syringe. Use a microsyringe and rapidly
inject the alcoholic standard into the water. Remove the needle as quickly
as possible after injection. Accurate calibration standards can be prepared
by injecting 20 µL of the primary dilution standards to 25 mL or more of
reagent water using the syringe described in Section 6.4.3. Aqueous
standards are not stable in volumetric container and should be discarded
after one hour unless transferred to sample bottle and sealed immediately
as described in Section 8.1.2.

9.2 Calibration

502.2-13
 9.2.1 Starting with the standard of lowest concentration, analyze each
calibration standard according to Section 11.0 and tabulate peak height or
area response versus the concentration in the standard. The results can
be used to prepare a calibration curve for each compound. Alternatively,
if the ratio of response to concentration (calibration factor) is a constant
over the working range (<10% relative standard deviation), linearity
through the origin can be assumed and the average ratio or calibration
factor can be used in place of a calibration curve.

9.2.2 The working calibration curve or calibration factor must be verified on

each working day by the measurement of one or more calibration
standards. If the response for any analyte varies from the predicted
response by more than ±20%, the test must be repeated using a fresh
calibration standard. If the results still do not agree, generate a new
calibration curve or use a single point calibration standard as described in
Section 9.2.3.

9.2.3 Single point calibration is a viable alternative to a calibration curve.

Prepare single point standards from the primary dilution standards in
methanol. The single point standards should be prepared at a
concentration that produces a response close (±20%) to that of the
unknowns.

9.2.4 As a second alternative to a calibration curve, internal standard calibration

techniques may be used. The organohalides recommended for this
purpose are: 1-chloro-2-fluorobenze or 2-bromo- 1-chloropropane and
fluorobenzene. The internal standard is added to the sample just before
purging. Check the validity of the internal standard calibration factors
daily by analyzing a calibration standard. Since the calculated
concentrations can be strongly biased by inaccurate detector response
measurements for the internal standard or by coelution of an unknown,
it is required that the area measurement of the internal standard of each
sample be within ±3 standard deviations of those obtained from
calibration standards. If they do not, then internal standards can not be
used.

9.3 Calibration for Vinyl Chloride Using a Certified Gaseous Mixture (Optional)

9.3.1 Fill the purging device with 5.0 mL of reagent water or aqueous
calibration standard, and add internal standards.

502.2-14
 9.3.2 Start to purge the aqueous mixture (Section 7.2.6). Inject a known volume
(between 100 and 2000 µL) of the calibration gas (at room temperature)
directly into the purging device with a gas tight syringe. Slowly inject the
gaseous sample through the aqueous sample inlet needle. After
completion, inject 2 mL of clean room air to sweep the gases from the inlet
needle into the purging device. Inject the gaseous standard before five
minutes of the 11-minute purge time have elapsed.

9.3.3 Determine the aqueous equivalent concentration of vinyl chloride standard

injected in µg/L, according to the equation:

where: S = Aqueous equivalent concentration of vinyl chloride

standard in µg/L;
C = Concentration of gaseous standard in ppm (v/v);
V = Volume of standard injected in milliliter

10.0 QUALITY CONTROL

10.1 Quality control (QC) requirements are the initial demonstration of laboratory
capability followed by regular analyses of laboratory reagent blanks, field reagent
blanks, and laboratory fortified blanks. The laboratory must maintain records to
document the quality of the data generated. Additional quality control practices
are recommended.

10.2 Initial demonstration of low system background. Before any samples are
analyzed, it must be demonstrated that a laboratory reagent blank (LRB) is
reasonably free of contamination that would prevent the determination of any
analyte of concern. Sources of background contamination are glassware, purge
gas, sorbents, and equipment. Background contamination must be reduced to an
acceptable level before proceeding with the next section. In general background
from method analytes should be below the method detection limit.

10.3 Initial demonstration of laboratory accuracy and precision. Analyze four to seven
replicates of a laboratory fortified blank containing each analyte of concern at a
concentration in the range of 0.1-5 µg/L (see regulations and maximum
contaminant levels for guidance on appropriate concentrations).

10.3.1 Prepare each replicate by adding an appropriate aliquot of a quality

control sample to reagent water. If a quality control sample containing the
method analytes is not available, a primary dilution standard made from
a source of reagents different than those used to prepare the calibration
standards may be used. Also add the appropriate amounts of internal
standard and surrogates if they are being used. Analyze each replicate
according to the procedures described in Section 11.0, and on a schedule
that results in the analyses of all replicates over a period of several days.

502.2-15
 10.3.2 Calculate the measured concentration of each analyte in each replicate, the
mean concentration of each analyte in all replicates, and mean accuracy
(as mean percentage of true value) for each analyte, and the precision (as
relative standard deviation, RSD) of the measurements for each analyte.
Calculate the MDL of each analyte using the procedures described in (4).

10.3.3 For each analyte and surrogate, the mean accuracy, expressed as a
percentage of the true value, should be 80-120% and the RSD should be
<20%. Some analytes, particularly the early eluting gases and late eluting
higher molecular weight compounds, are measured with less accuracy and
precision than other analytes. The method detection limits must be
sufficient to detect analytes at the regulatory levels. If these criteria are
not met for an analyte, take remedial action and repeat the measurements
for that analyte to demonstrate acceptable performance before samples are
analyzed.

10.3.4 Develop and maintain a system of control charts to plot the precision and
accuracy of analyte and surrogate measurements as a function of time.
Charting of surrogate recoveries is an especially valuable activity since
these are present in every sample and the analytical results will form a
significant record of data quality.

10.4 Laboratory Reagent Blanks -- With each batch of samples processed as a group
within a work shift, analyze a laboratory reagent blank to determine the
background system contamination.

10.5 With each batch of samples processed as a group within a work shift, analyze a
single laboratory fortified blank (LFB) containing each analyte of concern at a
concentration as determined in Section 10.3. If more than 20 samples are included
in a batch, analyze one LFB for every 20 samples. Use the procedures described
in Section 10.3.3 to evaluate the accuracy of the measurements, and to estimate
whether the method detection limits can be obtained. If acceptable accuracy and
method detection limits cannot be achieved, the problem must be located and
corrected before further samples are analyzed. Add these results to the on-going
control charts to document data quality.

10.6 With each set of field samples a field reagent blank (FRB) should be analyzed.
The results of these analyses will help define contamination resulting from field
sampling and transportation activities. An acceptable FRB may replace the LRB.

10.7 At least quarterly, replicates of laboratory fortified blanks should be analyzed to

determine the precision of the laboratory measurements. Add these results to the
on-going control charts to document data quality.

10.8 At least quarterly, analyze a quality control sample (QCS) from an external
source. If measured analyte concentrations are not of acceptable accuracy, check
the entire analytical procedure to locate and correct the problem source.

502.2-16
 10.9 Sample matrix effects have not been observed when this method is used with
distilled water, reagent water, drinking water, and ground water. Therefore,
analysis of a laboratory fortified sample matrix (LFM) is not required. It is
recommended that sample matrix effects be evaluated at least quarterly using the
QCS described in Section 10.8.

10.10 Numerous other quality control measures are incorporated into other parts of this
procedure, and serve to alert the analyst to potential problems.

11.0 PROCEDURE

11.1 Initial Conditions

11.1.1 Recommended chromatographic conditions are summarized in Section 6.3.

Other columns or element specific detectors may be used if the
requirements of Section 10.3 are met.

11.1.2 Calibrate the system daily as described in Section 9.2.

11.1.3 Adjust the purge gas (nitrogen or helium) flow rate to 40 mL/min. Attach
the trap inlet to the purging device and open the syringe valve on the
purging device.

11.2 Sample Introduction and Purging

11.2.1 To generate accurate data, samples and calibration standards must be

analyzed under identical conditions. Remove the plungers from two 5 mL
syringes and attach a closed syringe valve to each. Warm the sample to
room temperature, open the sample (or standard) bottle, and carefully
pour the sample into one of the syringe barrels to just short of
overflowing. Replace the syringe plunger, invert the syringe, and
compress the sample. Open the syringe valve and vent any residual air
while adjusting the sample volume to 5.0 mL. Add 10 µL of the internal
calibration standard to the sample through the syringe valve. Close the
valve. Fill the second syringe in an identical manner from the same
sample bottle. Reserve this second syringe for a reanalysis if necessary.

11.2.2 Attach the sample syringe valve to the syringe valve on the purging
device. Be sure that the trap is cooler than 25°C, then open the sample
syringe valve and inject the sample into the purging chamber. Close both
valves and initiate purging. Purge the sample for 11.0 ±0.1 min at
ambient temperature.

11.3 Sample Desorption -- After the 11-minute purge, couple the trap to the
chromatograph by switching the purge and trap system to the desorb mode,
initiate the temperature program sequence of the gas chromatograph and start
data acquisition. Introduce the trapped materials to the GC column by rapidly
heating the trap to 180°C while backflushing the trap with an appropriate inert

502.2-17
 gas flow for 4.0 ±0.1 min. While the extracted sample is being introduced into the
gas chromatograph, empty the purging device using the sample syringe and wash
the chamber with two 5 mL flushes of reagent water.

11.4 Trap Reconditioning -- After desorbing the sample for four min, recondition the
trap by returning the purge and trap system to the purge mode. Maintain the
trap temperature at 180°C. After approximately seven minutes, turn off the trap
heater and open the syringe valve to stop the gas flow through the trap. When
the trap is cool, the next sample can be analyzed.

12.0 CALCULATIONS

12.1 Identify each analyte in the sample chromatogram by comparing the retention
time of the suspect peak to retention times generated by the calibration standards,
the LFB and other fortified quality control samples. If the retention time of the
suspect peak agrees within ±3 standard deviations of the retention times of those
generated by known standards (Tables 1 and 3) then the identification may be
considered as positive. If the suspect peak falls outside this range or coelutes
with other compounds (Tables 1 and 3), then the sample should be reanalyzed.
When applicable, determine the relative response of the alternate detector to the
analyte. The relative response should agree to within 20% of the relative response
determined from standards.

12.2 Xylenes and other structural isomers can be explicitly identified only if they have
sufficiently different GC retention times. Acceptable resolution is achieved if the
height of the valley between two isomer peaks is less than 25% of the sum of the
two peak heights. Otherwise, structural isomers are identified as isomeric pairs.

12.3 When both detectors respond to an analyte, quantitation is usually performed on

the detector which exhibits the greater response. However, in cases where greater
specificity or precision would result, the analyst may choose the alternate
detector.

12.4 Determine the concentration of the unknowns by using the calibration curve or
by comparing the peak height or area of the unknowns to the peak height or area
of the standards as follows:

Concentration of unknown (µg/L) = (Peak height sample/Peak height standard)

x Concentration of standard (µg/L).

12.5 Calculations should utilize all available digits of precision, but final reported
concentrations should be rounded to an appropriate number of significant
figures(one digit of uncertainty). Experience indicates that three significant
figures may be used for concentrations above 99 µg/L, two significant figures for
concentrations between 1-99 µg/L, and 1 significant figure for lower
concentrations.

502.2-18
 12.6 Calculate the total trihalomethane concentrations by summing the four individual
trihalomethane concentrations in µg/L.

13.0 ACCURACY AND PRECISION

13.1 This method was tested in a single laboratory using reagent water fortified at 10
µg/L (1). Single laboratory precision and accuracy data for each detector are
presented for the method analytes in Tables 2 and 4.

13.2 Method detection limits for these analytes have been calculated from data
collected by fortifying reagent water at 0.1 µg/L.1. These data are presented in
Tables 2 and 4.

14.0 REFERENCES

1. Ho, J.S. A Sequential Analysis for Volatile Organics in Water by Purge and Trap
Capillary Column Gas Chromatograph with Photoionization and Electrolytic
Conductivity Detectors in Series, Journal of Chromatographic Science 27(2) 91-98,
February 1989.

2. Kingsley, B.A., Gin, C., Coulson, D.M., and Thomas, R.F. Gas Chromatographic
Analysis of Purgeable Halocarbon and Aromatic Compounds in Drinking Water
Using Two Detectors in Series, Water Chlorination, Environmental Impact and
Health Effects, Volume 4, Ann Arbor Science.

3. Bellar, T.A. and Lichtenberg, J.J. The Determination of Halogenated Chemicals

in Water by the Purge and Trap Method, Method 502.1, U.S. Environmental
Protection Agency, Environmental Monitoring and Support Laboratory,
Cincinnati, Ohio 45268, April 1981.

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

5. Carcinogens - Working with Carcinogens, Department of Health, Education, and

Welfare, Public Health Service, Center for Disease Control, National Institute for
Occupational Safety and Health, Publication No. 77-206, August 1977.

6. OSHA Safety and Health Standards, (29 CFR 1910), Occupational Safety and
Health Administration, OSHA 2206.

7. Safety in Academic Chemistry Laboratories, American Chemical Society

Publication, Committee on Chemical Safety, 4th Edition, 1985.

8. Bellar, T.A. and Lichtenberg, J.J. The Determination of Synthetic Organic

Compounds in Water by Purge and Sequential Trapping Capillary Column Gas
Chromatography, U.S. Environmental Protection Agency, Environmental
Monitoring and Support Laboratory, Cincinnati, Ohio 45268.

502.2-19
9. Slater, R.W., Graves, R.L., and McKee, G.D. "A Comparison of Preservation
Techniques for Volatile Organic Compounds in Chlorinated Tap Waters," U.S.
Environmental Protection Agency, Environmental Monitoring and Support
Laboratory, Cincinnati, Ohio 45268.

502.2-20
 TABLE 1. RETENTION TIMES FOR VOLATILE ORGANIC COMPOUNDS ON
PHOTOIONIZATION DETECTOR (PID) AND ELECTROLYTIC
CONDUCTIVITY DETECTOR (ELCD) FOR COLUMN 1
Retention Time (min)a
Analyteb PID ELCD
1 Dichlorodifluoromethane –c 8.47
2 Chloromethane – 9.47
3 Vinyl Chloride 9.88 9.93
4 Bromomethane – 11.95
5 Chloroethane – 12.37
6 Trichlorofluoromethane – 13.49
7 1,1-Dichloroethene 6.14 16.18
8 Methylene Chloride – 18.39
9 trans-1,2-Dichloroethene 19.30 19.33
10 1,1-Dichloroethane – 20.99
11 2,2-Dichloropropane – 22.88
12 cis-1,2-Dichloroethene 23.11 23.14
13 Chloroform – 23.64
14 Bromochloromethane – 24.16
15 1,1,1-Trichloroethane – 24.77
16 1,1-Dichloropropene 25.21 25.24
17 Carbon Tetrachloride – 25.47
18 Benzene 26.10 –
19 1,2-Dichloroethane – 26.27
20 Trichloroethene 27.99 28.02
21 1,2-Dichloropropane – 28.66
22 Bromodichloromethane – 29.43
23 Dibromomethane – 29.59
Cis-1,3-Dichloropropene 31.38 31.41
24 Toluene 31.95 –
Trans-1,3-Dichloropropene 33.01 33.04
25 1,1,2-Trichloroethane – 33.21
26 Tetrachloroethene 33.88 33.90
27 1,3-Dichloropropane – 34.00
28 Dibromochloromethane – 34.73
29 1,2-Dibromoethane – 35.34
30 Chlorobenzene 36.56 36.59
31 Ethylbenzene 36.72 –
32 1,1,1,2-Tetrachloroethane – 36.80
33 m-Xylene 36.98 –
34 p-Xylene 36.98 –
35 o-Xylene 38.39 –
36 Styrene 38.57 –
37 Isopropylbenzene 39.58 –
38 Bromoform – 39.75
39 1,1,2,2-Tetrachloroethane – 40.35
40 1,2,3-Trichloropropane – 40.81
41 n-Propylbenzene 40.87 –
42 Bromobenzene 40.99 41.03
43 1,3,5-Trimethylbenzene 41.41 –

502.2-21
 TABLE 1. RETENTION TIMES FOR VOLATILE ORGANIC COMPOUNDS ON
PHOTOIONIZATION DETECTOR (PID) AND ELECTROLYTIC
CONDUCTIVITY DETECTOR (ELCD) FOR COLUMN 1
Retention Time (min)a
Analyteb PID ELCD
44 2-Chlorotoluene 41.41 41.45
45 4-Chlorotoluene 41.60 41.63
46 tert-Butylbenzene 42.71 –
47 1,2,4-Trimethylbenzene 42.92 –
48 sec-Butylbenzene 43.31 –
49 p-Isopropyltoluene 43.81 –
50 1,3-Dichlorobenzene 44.08 44.11
51 1,4-Dichlorobenzene 44.43 44.47
52 n-Butylbenzene 45.20 –
53 1,2-Dichlorobenzene 45.71 45.74
54 1,2-Dibromo-3-Chloropropane – 48.57
55 1,2,4-Trichlorobenzene 51.43 51.46
56 Hexachlorobutadiene 51.92 51.96
57 Naphthalene 52.38 –
58 1,2,3-Trichlorobenzene 53.34 53.37
Internal Standards
Fluorobenzene 26.84 –
2-Bromo-1-chloropropaned – 33.08
a
Column and analytical conditions are described in Section 6.3.
b
Number refers to peaks in Figure 502.2-1.
c
Dash indicates detector does not respond.
d
Interferes with trans-1,3-dichloropropene and 1,1,2-trichloroethane on the column. Use
with care.

502.2-22
 TABLE 2. SINGLE LABORATORY ACCURACY, PRECISION, AND METHOD DETECTION LIMITS FOR
VOLATILE ORGANIC COMPOUNDS IN REAGENT WATER FOR COLUMN 1
Photoionization Detector Electrolytic Conductivity Detector
Average Rel. Std. Average Rel. Std.
Recovery Deviation MDL Recovery Deviation MDL
(µg/L) (%) (µg/L) (µg/L) (%) (µg/L)
Benzene 99 1.2 0.01 – – –
Bromobenzene 99 1.7 0.01 97 2.7 0.03
Bromochloromethane – – – 96 3.0 0.01
Bromodichloromethane – – – 97 2.9 0.02
Bromoform – – – 106 5.2 1.6
Bromomethane – – – 97 3.8 1.1
n-Butylbenzene 100 4.4 0.02 – – –
sec-Butylbenzene 97 2.7 0.02 – – –
tert-Butylbenzene 98 2.3 0.06 – – –
502.2-23

Carbon tetrachloride – – – 92 3.6 0.01

Chlorobenzene 100 1.0 0.01 103 3.6 0.01
Chloroethane – – – 96 3.9 0.1
Chloroform – – – 98 2.5 0.02
Chloromethane – – – 96 9.2 0.03
2-Chlorotoluene N.D. N.D. c N.D. 97 2.7 0.01
4-Chlorotoluene 101 1.0 0.02 97 3.2 0.01
1,2-Dibromo-3-chloropropane – – – 86 11.3 3.0
Dibromochloromethane – – – 102 3.3 0.3
1,2-Dibromoethane – – – 97 2.8 0.8
Dibromomethane – – – 109 6.7 2.2
1,2-Dichlorobenzene 102 2.1 0.05 100 1.5 0.02
1,3-Dichlorobenzene 104 1.6 0.02 106 4.0 0.02
1,4-Dichlorobenzene 103 2.1 0.01 98 2.3 0.01
Dichlorodifluoromethane – – – 89 6.6 0.05
1,1-Dichloroethane – – – 100 5.7 0.07
 TABLE 2. SINGLE LABORATORY ACCURACY, PRECISION, AND METHOD DETECTION LIMITS FOR
VOLATILE ORGANIC COMPOUNDS IN REAGENT WATER FOR COLUMN 1
Photoionization Detector Electrolytic Conductivity Detector
Average Rel. Std. Average Rel. Std.
Recovery Deviation MDL Recovery Deviation MDL
(µg/L) (%) (µg/L) (µg/L) (%) (µg/L)
1,2-Dichloroethane – – – 100 3.8 0.03
1,1-Dichloroethene 100 2.4 N.D. 103 2.8 0.07
cis-1,2 Dichloroethene N.D. N.D. 0.02 105 3.3 0.01
trans-1,2-Dichloroethene 93 4.0 0.05 99 3.7 0.06
1,2-Dichloropropane – – – 103 3.7 0.01
1,3-Dichloropropane – – – 100 3.4 0.03
2,2-Dichloropropane – – – 105 3.4 0.05
1,1-Dichloropropene 103 3.5 0.02 103 3.3 0.02
Ethylbenzene 101 1.4 0.01 – – –
502.2-24

Hexachlorobutadiene 99 9.5 0.06 98 8.3 0.02

Isopropylbenzene 98 0.9 0.05 – – –
p-Isopropyltoluene 98 2.4 0.01 – – –
Methylene chloride – – – 97 2.9 0.02
Naphthalene 102 6.2 0.06 – – –
n-Propylbenzene 103 2.0 0.01 – – –
Styrene 104 1.3 0.01 – – –
1,1,1,2-Tetrachloroethane – – – 99 2.3 0.01
1,1,2,2-Tetrachloroethane – – – 99 6.8 0.01
Tetrachloroethene 101 1.8 0.05 97 2.5 0.04
Toluene 99 0.8 0.01 – – –
1,2,3-Trichlorobenzene 106 1.8 N.D. 98 3.1 0.03
1,2,4-Trichlorobenzene 104 2.2 0.02 102 2.1 0.03
1,1,1-Trichloroethane – – – 104 3.3 0.03
1,1,2-Trichloroethane – – – 109 5.6 N.D.
Trichloroethene 100 0.78 0.02 96 3.6 0.01
Trichlorofluoromethane – – – 96 3.5 0.03
 TABLE 2. SINGLE LABORATORY ACCURACY, PRECISION, AND METHOD DETECTION LIMITS FOR
VOLATILE ORGANIC COMPOUNDS IN REAGENT WATER FOR COLUMN 1
Photoionization Detector Electrolytic Conductivity Detector
Average Rel. Std. Average Rel. Std.
Recovery Deviation MDL Recovery Deviation MDL
(µg/L) (%) (µg/L) (µg/L) (%) (µg/L)
1,2,3-Trichloropropane – – – 99 2.3 0.4
1,2,4-Trimethylbenzene 99 1.2 0.05 – – –
502.2-25

1,3,5-Trimethylbenzene 101 1.4 0.01 – – –

Vinyl chloride 109 5.0 0.02 95 5.9 0.04
o-Xylene 99 0.8 0.02 – – –
m-Xylene 100 1.4 0.01 – – –
p-Xylene 99 0.9 0.01 – – –
a
Recoveries and relative standard deviations were determined from seven samples fortified at 10 µg/L of each analyte.
Recoveries were determined by internal standard method. Internal standards were: Fluorobenzene for PID,
2-Bromo-1-chloropropane for ELCD.
b
Detector does not respond.
c
N.D. = not determined.
 TABLE 3. RETENTION TIMES FOR VOLATILE ORGANIC COMPOUNDS ON
PHOTOIONIZATION DETECTOR (PID) AND ELECTROLYTIC
CONDUCTIVITY DETECTOR (ELCD) FOR COLUMN 2
Retention Time (min)a
and Rel. Std. Dev.
Analyte PID RSD ELCD RSD
c
1 Dichlorodifluoromethane – 7.36 0.06
2 Chloromethane – 8.09 0.06
3 Vinyl Chloride 8.57 0.06 8.58 0.08
4 BromomethanE – 10.39 0.06
5 Chloroethane – 10.74 0.05
6 Trichlorofluoromethane – 11.85 0.07
7 1,1-Dichloroethene 14.46 0.08 14.47 0.07
8 Methylene Chloride – 16.46 0.04
9 trans-1,2-Dichloroethene 17.61 0.02 17.62 0.03
10 1,1-Dichloroethane – 19.25 0.03
11 2,2-Dichloropropane – 21.36 0.03
12 cis-1,2-Dichloroethene 21.52 0.02 21.52 0.02
13 Chloroform – 22.08 0.02
14 Bromochloromethane – 22.69 0.02
15 1,1,1-Trichloroethane – 23.53 0.02
16 1,1-Dichloropropene 24.07 0.01 24.08 0.02
17 Carbon Tetrachloride – 24.47 0.02
18 1,2-Dichloroethane – 24.95 0.01
19 Benzene 25.06 0.01 –
20 Trichloroethene 27.99 0.01 27.15 0.01
21 1,2-Dichloropropane – 27.73 0.01
22 Bromodichloromethane – 28.57 0.02
23 Dibromomethane – 28.79 0.01
24 Cis-1,3-Dichloropropene 30.40 0.01 30.41 0.02
25 Toluene 31.58 0.01 –
26 Trans-1,3-Dichloropropene 32.11 0.01 32.13 0.01
27 1,1,2-Trichloroethane – 32.69 0.01
28 1,3-Dichloropropane – 33.57 0.01
29 Tetrachloroethene 33.85 0.01 33.86 0.01
30 Dibromochloromethane – 34.58 0.01
31 1,2-Dibromoethane – 35.29 0.01
32 Chlorobenzene 36.76 0.01 36.87 0.01
33 1,1,1,2-Tetrachloroethane – 36.87 0.01
34 Ethylbenzene 36.92 0.01 –
35 m-Xylene 37.19 0.01 –
36 p-Xylene 37.19 0.01 –
37 o-Xylene 38.77 0.01 –
38 Styrene 38.90 0.01 –
39 Isopropylbenzene 40.04 0.01 –
40 Bromoform – 40.19 0.01
41 1,1,2,2-Tetrachloroethane – 40.64 0.01
42 1,2,3-Trichloropropane – 0.01 41.18 0.01
43 n-Propylbenzene 41.51 0.01 –
44 Bromobenzene 41.73 0.01 41.75 0.01

502.2-26
 TABLE 3. RETENTION TIMES FOR VOLATILE ORGANIC COMPOUNDS ON
PHOTOIONIZATION DETECTOR (PID) AND ELECTROLYTIC
CONDUCTIVITY DETECTOR (ELCD) FOR COLUMN 2
Retention Time (min)a
and Rel. Std. Dev.
Analyte PID RSD ELCD RSD
45 1,3,5-Trimethylbenzene 42.08 0.01 –
46 2-Chlorotoluene 42.20 0.01 42.21 0.01
47 4-Chlorotoluene 42.36 0.01 42.36 0.01
48 tert-Butylbenzene 43.40 0.01 –
49 1,2,4-Trimethylbenzene 43.55 0.01 –
50 sec-Butylbenzene 44.19 0.01 –
51 p-Isopropyltoluene 44.69 0.01 –
52 1,3-Dichlorobenzene 45.08 0.01 45.09 0.01
53 1,4-Dichlorobenzene 45.48 0.01 45.48 0.01
54 n-Butylbenzene 46.22 0.01 –
55 1,2-Dichlorobenzene 46.88 0.01 46.89 0.01
56 1,2-Dibromo-3-Chloropropane – 49.84 0.01
57 1,2,4-Trichlorobenzene 53.26 0.01 53.26 0.01
58 Hexachlorobutadiene 53.86 0.01 53.87 0.01
59 Naphthalene 54.45 0.01 –
60 1,2,3-Trichlorobenzene 55.54 0.01 55.54 0.01

Internal Standards
1-Chloro-2-Fluorobenzene 37.55 0.01 37.56 0.01
a
Column and analytical conditions are described in Section 6.3.4.
b
Number refers to peaks in Figure 502.2-2.
c
Dash indicates detector does not respond.

502.2-27
 TABLE 4. SINGLE LABORATORY ACCURACY, PRECISION, AND METHOD DETECTION LIMITS FOR
VOLATILE ORGANIC COMPOUNDS IN REAGENT WATER FOR COLUMN 2
Photoionization Detector Electrolytic Conductivity Detector
Average Rel. Std. Average Rel. Std.
Recovery Deviation MDL Recovery Deviation MDL
(µg/L) (%) (µg/L) (µg/L) (%) (µg/L)
Benzene 97 1.6 0.01 – – –
Bromobenzene 98 1.1 0.04 96 3.2 0.14
Bromochloromethane- – – – 95 2.5 0.01
Bromodichloromethane – – – 96 2.6 0.10
Bromoform – – – 98 4.0 0.09
Bromomethane – – – 97 2.4 0.19
n-Butylbenzene 95 2.4 0.03 – – –
sec-Butylbenzene 96 2.1 0.03 – – –
tert-Butylbenzene 98 2.1 0.06 – – –
502.2-28

Carbon tetrachloride – – – 97 2.4 0.02

Chlorobenzene 98 1.5 0.02 98 2.2 N.D.
Chloroethane – – – 97 3.2 0.13
Chloroform – – – 92 4.2 0.01
Chloromethane – – – 98 2.3 0.10
2-Chlorotoluene 94 3.1 0.03 99 2.3 0.04
4-Chlorotoluene 97 1.6 0.02 97 2.3 0.07
1,2-Dibromo-3-chloropropane – – – 97 2.2 0.20
Dibromochloromethane – – – 99 2.0 0.05
1,2-Dibromoethane – – – 99 2.8 0.17
Dibromomethane – – – 98 3.5 0.10
1,2-Dichlorobenzene 97 1.4 0.03 98 2.0 0.04
1,3-Dichlorobenzene 97 1.6 0.02 97 2.2 0.07
1,4-Dichlorobenzene 97 1.5 0.03 97 2.2 0.04
Dichlorodifluoromethane – – – 96 3.2 0.29
1,1-Dichloroethane – – – 97 2.3 0.03
1,2-Dichloroethane – – – 98 1.8 0.03
1,1-Dichloroethene 96 2.2 0.10 97 2.3 0.04
 TABLE 4. SINGLE LABORATORY ACCURACY, PRECISION, AND METHOD DETECTION LIMITS FOR
VOLATILE ORGANIC COMPOUNDS IN REAGENT WATER FOR COLUMN 2
Photoionization Detector Electrolytic Conductivity Detector
Average Rel. Std. Average Rel. Std.
Recovery Deviation MDL Recovery Deviation MDL
(µg/L) (%) (µg/L) (µg/L) (%) (µg/L)
cis-1,2 Dichloroethene 97 1.7 0.03 96 3.3 0.05
trans-1,2-Dichloroethene 97 1.8 0.03 98 1.5 0.05
1,2-Dichloropropane – – – 98 1.8 0.03
1,3-Dichloropropane – – – 100 1.3 0.02
2,2-Dichloropropane – – – 95 14.2 N.D.
1,1-Dichloropropene 96 2.1 0.05 97 2.6 0.02
Cis-1,3-Dichloropropene 98 1.6 0.06 98 2.0 0.08
Trans-1,3-Dichloropropene 99 1.7 0.06 97 1.4 0.10
Ethylbenzene 98 1.2 0.04 – – –
502.2-29

Hexachlorobutadiene 95 2.6 0.09 97 2.3 0.05

Isopropylbenzene 97 1.4 0.02 – – –
p-Isopropyltoluene 96 2.0 0.02 – – –
Methylene chloride – – – 100 3.1 0.01
Naphthalene 96 2.1 0.02 – – –
n-Propylbenzene 97 1.8 0.03 – – –
Styrene 96 1.9 0.10 – – –
1,1,1,2-Tetrachloroethane – – – 98 2.2 N.D.
1,1,2,2-Tetrachloroethane – – – 100 2.8 0.02
Tetrachloroethene 97 1.6 0.04 97 1.9 0.02
Toluene 98 1.3 0.02 – – –
1,2,3-Trichlorobenzene 95 2.3 0.05 98 2.8 0.06
1,2,4-Trichlorobenzene 94 3.0 0.06 96 2.5 0.08
1,1,1-Trichloroethane – – – 96 2.6 0.01
1,1,2-Trichloroethane – – – 99 1.6 0.04
Trichloroethene 97 1.7 0.03 98 1.2 0.06
Trichlorofluoromethane – – – 97 6.0 0.34
 TABLE 4. SINGLE LABORATORY ACCURACY, PRECISION, AND METHOD DETECTION LIMITS FOR
VOLATILE ORGANIC COMPOUNDS IN REAGENT WATER FOR COLUMN 2
Photoionization Detector Electrolytic Conductivity Detector
Average Rel. Std. Average Rel. Std.
Recovery Deviation MDL Recovery Deviation MDL
(µg/L) (%) (µg/L) (µg/L) (%) (µg/L)
1,2,3-Trichloropropane – – – 100 2.0 0.02
1,2,4-Trimethylbenzene 96 2.0 0.02 – – –
502.2-30

1,3,5-Trimethylbenzene 98 1.6 0.03 – – –

Vinyl chloride 95 1.1 0.01 96 2.6 0.18
o-Xylene 98 1.1 0.02 – – –
m-Xylene 98 1.1 0.02 – – –
p-Xylene 98 0.9 0.02 – – –
a
Recoveries and relative standard deviations were determined from seven samples fortified at 10 µg/L of each analyte.
Recoveries were determined by external standard method.
b
Detector does not respond.
c
N.D. = not determined.
502.2-31
502.2-32
502.2-33
502.2-34