3125

Metals by I nductively Coupled Plasma-Mass Spectrometry

Approved by Standard Methods Committee, 2009. Editorial revisions, 2011 and 2020. Joint Task Group: 22nd Edition—Robert Henry (chair), Christopher J. Baggett, Cindy
A. Bamfield, Alois F. Clary, William R. Kammin, Gregg Oelker.

3125 A. Introduction

1. General Discussion Table 3125:2. Method Performance with Standard Reference Watera
Mean
This method is designed to determine trace metals and met- Recovery Mean SD RSD
alloids in surface, ground, and drinking waters via inductively Element Mass (%) (ng/mL) (ng/mL) (%)
coupled plasma-mass spectrometry (ICP-MS). Although best
V 51 95.49 12.40 0.62 5.01
suited for ambient or pristine freshwater matrices, this method
V CCT 51 101.60 13.20 0.32 2.39
can also be used to analyze wastewater, soils, sediments, sludge, Cr 52 93.34 36.03 0.80 2.21
and biological samples after appropriate digestion followed by Cr CCT 52 95.31 36.79 0.89 2.42
dilution and cleanup to reduce matrix effects to a manageable Mn 55 99.09 120.40 2.25 1.87
level.1,2 Various cleanup techniques are available to reduce matrix Mn CCT 55 96.99 117.8 2.18 1.85
interferences and concentrate the analytes of interest.3–7 Fe 56 110.45 37.89 4.32 11.41
For many analytes, the instrument detection limits (IDLs) are Fe CCT 56 102.20 35.06 1.78 5.09
between 1 and 100 ng/L. The quadrupole-based ICP-MS may Co 59 98.43 19.96 0.32 1.62
include collision cell technology (CCT) and dynamic reaction Co CCT 59 99.22 20.12 0.36 1.79
cell (DRC), which remove the need for mathematical interference Ni 60 98.78 27.06 0.68 2.51
Ni CCT 60 100.69 27.59 0.50 1.80
correction for many elements. Additional data (Tables 3125:1
Cu 63 115.36 98.29 3.68 3.74
and 3125:2) demonstrate the performance for elements seriously
Cu CCTb 63 122.91 104.7 2.81 2.68
affected by polyatomic interferences.8,9 Cub 65 118.83 101.2 2.84 2.80
Zn 66 95.88 51.01 1.36 2.67
Table 3125:1. Method Performance with Calibration Verification Zn CCT 66 97.64 51.95 1.91 3.68
Standards (N = 28)a As 75 98.61 26.30 0.48 1.81
Mean As CCT 75 98.38 26.24 0.59 2.26
Recovery Mean SD RSD Se 78 95.83 21.04 0.45 2.15
Se CCT 78 97.58 21.43 1.86 8.66
Element Mass (%) (ng/mL) (ng/mL) (%)
CCT = collision cell technology; RSD = relative standard deviation; SD = standard
V 51 100.00 200.0 9.25 4.62 deviation.
V CCT 51 100.44 200.9 7.30 3.63 a
Single-laboratory, single-operator data acquired 12-2005 using Thermo Electron
Cr 52 99.56 199.1 9.39 4.72 X Series in Standard and CCT-KED modes; NIST 1640 (N = 7).
Cr CCT 52 100.56 201.1 7.16 3.56 b
Copper contamination.
Mn 55 101.36 1014 54.09 5.34
Mn CCT 55 98.28 982.8 31.95 3.25 The method is intended to be performance-based, so the ele-
Fe 56 101.84 10184 566.43 5.56 mental analyte list can be extended, new preparation techniques
Fe CCT 56 100.25 10025 336.29 3.35 can be implemented, and other appropriate modifications can
Co 59 101.58 20.32 0.89 4.38 be made as technology evolves. Any modifications to the base
Co CCT 59 101.67 20.33 0.64 3.15 method must be validated via suitable quality control standards.
Ni 60 101.08 202.2 9.06 4.48
More sources of information on quality assurance and other
Ni CCT 60 101.90 203.8 6.61 3.24
Cu 63 101.76 1018 62.46 6.14 aspects of ICP-MS analysis of metals are available.10–12
Cu CCT 63 105.63 1056 36.79 3.48 Ideally, the analysts who use this method will have experience
Cu 65 102.12 1021 56.06 5.49 using ICP-MS, interpreting spectral and matrix interferences, and
Zn 66 100.52 1005 47.63 4.74 implementing corrective procedures. Before generating data, analysts
Zn CCT 66 99.51 995.1 33.94 3.41 should demonstrate their proficiency in this method by successfully
As 75 99.54 19.91 1.02 5.14 analyzing a performance evaluation sample for each matrix type.
As CCT 75 98.24 19.65 0.78 3.99
Se 78 102.77 20.55 1.04 5.07 References
Se CCT 78 104.78 20.96 1.73 8.26
CCT = collision cell technology. 1. Montaser A, Golightly DW, eds. Inductively coupled plasmas in ana-
a
Single-laboratory, single-operator data acquired 12-2005 using Thermo Electron lytical atomic spectrometry, 2nd ed. New York (NY): VCH Publishers,
X Series in Standard and CCT-KED modes. Inc.; 1992.

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 3125 METALS BY INDUCTIVELY COUPLED PLASMA-MASS SPECTROMETRY - B. ICP-MS Method

2. Date AR, Gray AL. Applications of inductively coupled plasma mass water samples. Olympia (WA): Puget Sound Water Quality Authority;
spectrometry. Glasgow (UK): Blackie & Son, Ltd.; 1989. 1996.
3. McLaren JW, Mykytiuk AP, Willie SN, Berman SS. Determination 8. Nelms S, ed. Inductively coupled plasma mass spectrometry hand-
of trace metals in seawater by inductively coupled plasma mass spec- book., Cambridge (MA): Blackwell Science; 2005
trometry with preconcentration on silica-immobilized 8-hydroxy- 9. Becker JS. Inorganic mass spectrometry: principles and applications.
quinoline. Anal Chem. 1985;57(14):2907–2911. Malden (MA): Wiley Interscience; 2008.
4. Burba P, Willmer PG. Multielement preconcentration for atomic 10. U.S. Environmental Protection Agency. Determination of trace ele-
spectroscopy by sorption of dithiocarbamate-metal complexes ments in waters and wastes by inductively coupled plasma-mass
(e.g., HMDC) on cellulose collectors. Fresenius Z Anal Chem. spectrometry; Method 200.8. Cincinnati (OH): Environmental
1987;329:539–545. Monitoring Systems Laboratory, Environmental Protection Agency;
5. Wang X, Barnes RM. Chelating resins for on-line flow injection 1994.
preconcentration with inductively coupled plasma atomic emission 11. Longbottom JE, Martin TD, Edgell KW, Long SE, Plantz MR, War-
spectroscopy. J Anal Atom Spectrom. 1989;4(6):509–518. den BE. Determination of trace elements in water by inductively
6. Siriraks A, Kingston HM, Riviello JM. Chelation ion chroma- coupled plasma-mass spectrometry: collaborative study. J AOAC
tography as a method for trace elemental analysis in complex Internat. 1994;77(4):1004–1023.
environmental and biological samples. Anal Chem. 1990;62(11): 12. U.S. Environmental Protection Agency. Method 1638: Determi-
1185–1193. nation of trace elements in ambient waters by inductively coupled
7. Puget Sound Water Quality Authority. Recommended guidelines for plasma-mass spectrometry. Washington DC: Office of Water, U.S.
measuring metals in Puget Sound marine water, sediment and tissue Environmental Protection Agency; 1995.
samples. Appendix D: Alternate methods for the analysis of marine

3125 B. Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) Method

1. General Discussion Table 3125:3. Recommended Analyte Masses, Instrument Detection

Limits (IDLs), and Internal Standards
a. Principle: In this method, analysts introduce sample mate- Recommended
a
rial to an argon-based, high-temperature radio-frequency plasma, Analytical IDL Internal
usually via pneumatic nebulization. As energy transfers from the Element Mass (µg/L) Standard
plasma to the sample stream, the target element desolves, atom-
Be 9 0.025 Li
izes, and ionizes. The resulting ions are extracted from the plasma Al 27 0.03 Sc
through a differential vacuum interface and separated based on V 51 0.02 Sc
their mass-to-charge (m/z) ratio by a mass spectrometer. Typically, Cr 52 0.04 Sc
either a quadrupole (with or without CCT or DRC) or magnetic Cr 53 0.03 Sc
sector (high-resolution) mass spectrometer is used. An electron Mn 55 0.002 Sc
Co 59 0.002 Sc
multiplier detector counts the separated ions, and a computer-based Ni 60 0.004 Sc
data-management system processes the resulting information. Ni 62 0.025 Sc
b. Applicable elements and analytical limits: This method has Cu 63 0.003 Sc
been demonstrated to be suitable for aluminum, antimony, arsenic, Cu 65 0.004 Sc
barium, beryllium, cadmium, chromium, cobalt, copper, lead, man- Zn 66 0.017 Ge
ganese, molybdenum, nickel, selenium, silver, strontium, thallium, Zn 68 0.020 Ge
As 75 0.025 Ge
uranium, vanadium, and zinc (see Table 3125:3). It is also accept- Se 77 0.093 Ge
able for other elemental analytes as long as the same quality assur- Se 82 0.064 Ge
ance practices are followed, with documented acceptance limits. Ag 107 0.003 In
Before implementing the method, determine the instrument Ag 109 0.002 In
detection limit (IDL) and method detection limit (MDL) for all Cd 111 0.006 In
Cd 114 0.003 In
analytes (see Section 1030 C). Typical IDLs for method analytes Sb 121 0.07 In
are presented in Table 3125:3.1,2 Sb 123 0.07 In
Determining the MDL for each element is critical when ana- Tl 203 0.03 Th
lyzing complex matrices, such as seawater, brines, and industrial Tl 205 0.03 Th
effluents. In these cases, the MDL typically will be higher than the Pb 208 0.005 Th
IDL because of background levels of analytes introduced during U 235 0.032 Th
U 238 0.001 Th
sample preparation, as well as laboratory-derived contamination Mo 98 0.003b In
and matrix-based interferences. Determine both IDL and MDL Ba 135 0.008b In
when first implementing this method, and then repeat yearly or Sr 88 0.001c In
whenever the instrument configuration changes or major mainte- a
IDLs were determined on a Perkin Elmer Elan 6000 ICP-MS using 7 replicate anal-
nance occurs, whichever happens first. yses of a 1% nitric acid solution, at Manchester Environmental Laboratory, July 1996.
Also, determine the linear dynamic range (LDR) for all method b
From EPA Method 200.8 for the Analysis of Drinking Waters—Application
analytes, including multi-element mixtures (to account for possible Note, Order No. ENVA-300A, The Perkin Elmer Corporation, 1996.
interelement effects). LDR is the maximum analyte concentration c
From Perkin Elmer Technical Summary TSMS-12.

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 3125 METALS BY INDUCTIVELY COUPLED PLASMA-MASS SPECTROMETRY - B. ICP-MS Method

Table 3125:4. Elemental Abundance Equations and Common Molecular will contribute to or obscure adjacent masses. Adjust the mass
Ion Correction Equations spectrometer resolution and quadrupole pole bias to minimize
these interferences.
Elemental and Molecular Equationsa
3) Polyatomics—Polyatomics are (molecular) ion interfer-
Li 6 =C6 ences caused by ions with more than one atom that have the
Be 9f =C9 same nominal m/z ratio as the isotope of interest. Most of the
Al 27 = C 27 common molecular ion interferences have been identified (see
Sc 45 = C 45 Table 3125:5). Because of the severity of chloride ion interfer-
V 51 = C 51 − (3.127)[(C 53) − (0.113 × C 52)] ence on important analytes, particularly vanadium and arsenic,
Cr 52 = C 52 hydrochloric acid is not recommended for use in ICP-MS sample
Cr 53 = C 53
preparation. Because most environmental samples contain some
Mn 55 = C 55
Co 59 = C 59 chloride ion, analysts must use chloride-correction equations for
Ni 60 = C 60 affected masses. Collision cell technology and dynamic reaction
Ni 62 = C 62 cell effectively reduce most polyatomic species to analytically
Cu 63 = C 63 negligible levels in quadrupole-based ICP-MS systems, some-
Cu 65 = C 65 times removing the need for complex correction equations. A
Zn 66 = C 66 high-resolution ICP-MS resolves many—but not all—interfer-
Zn 68 = C 69 ences caused by polyatomic ions. Polyatomic interferences are
As 75 = C 75 − (3.127)[(C 77) − (0.815 × C 82)] strongly influenced by instrument design and plasma operating
Se 77 = C 77 conditions; they sometimes can be reduced by carefully adjusting
Se 82 = C 82 − (1.008696 × C 83) nebulizer gas flow and other instrument operating parameters.
Sr 88 = C 88
4) Doubly-charged—Some elements (e.g., barium and stron-
Mo 98 = C 98 − (0.110588 × C 101)
Rh 103 = C 103 tium) form significant levels of M2+ ions under normal plasma
Ag 107 = C 107 conditions. The M2+ ions occur in the mass spectrum at M/2 and,
Ag 109 = C 109 in the case of Ba and Sr, will interfere with some isotopes of zinc
Cd 111 = C 111 − (1.073)[(C 108) − (0.712 × C 106)] and calcium, respectively.
Cd 114 = C 114 − (0.02686 × C 119) 5) Physical interferences—These include differences in vis-
Sb 121 = C 121 cosity, surface tension, and dissolved solids between samples
Sb 123 = C 123 − (0.127189 × C 125) and calibration standards. To minimize these effects, analytical
Ba 135 = C 135 samples should not contain more than 0.5% of dissolved solids.
Ho 165 = C 165
Dilute water and wastewater samples with higher dissolved solids
Tl 203 = C 203
levels before analyzing them. Use internal standards to correct for
Tl 205 = C 205
Pb 208 = C 208 + (1 × C 206) + (1 × C 207) physical interferences, provided that their analytical behavior is
Th 232 = C 232 comparable to the elements being determined.
U 238 = C 238 Table 3125:6 includes information on each isotope and cau-
C = calibration blank-corrected counts at indicated masses. tions on using correction equations. Quadrupole ICP-MS with
a
From EPA Method 200.8 for the Analysis of Drinking Water—Application CCT or DRC is recommended for all analytes, except perhaps
Note, Order No. ENVA-300A, The Perkin Elmer Corporation, 1996. beryllium (due to lower sensitivity), because it eliminates many
of the equations typically needed in the standard operating mode.
above the highest calibration point at which the analyte response 6) Memory interferences—These occur when analytes from a
is within ±10% of its theoretical response. When determining previous sample or standard are measured in the current sample.
LDRs, avoid using unnecessarily high analyte concentrations Use a long enough rinse (flush) between samples to minimize
because they might damage the detector. Determine LDR when such interferences. Persistent memory interferences may indicate
first implementing this method, and then repeat yearly. problems in the sample-introduction system. Severe memory
c. Interferences: ICP–MS is subject to several types of interfer- interferences may require analysts to disassemble and clean the
ences, including the following: entire sample-introduction system, including the plasma torch
1) Isobars—Isobars are isotopes of different elements that and the sampler and skimmer cones.
form ions with the same nominal atomic mass units/charge num- 7) Ionization interferences—These result when moderate
ber (m/z) ratio that cannot be resolved by a quadrupole or high- (0.1% to 1%) amounts of a matrix ion change the analyte sig-
resolution mass spectrometer. Typically, ICP-MS operating soft- nal. This effect, which usually reduces the analyte signal, also is
ware includes all known isobaric interferences and will perform known as suppression. Correct for suppression by using internal
the necessary calculations automatically (see Table 3125:4). Mon- standardization techniques.
itor 83Kr, 99Ru, 118Sn, and 125Te to correct for isobaric interference d. Quality control (QC): The QC practices considered to be an
caused by 82Kr on 82Se, by 98Ru on 98Mo, by 114Sn on 114Cd, by 115Sn integral part of each method can be found in Section 3020.
on 115In, and by 123Te on 123Sb. Monitor ArCl at mass 77 to estimate
chloride interferences. Verify that all elemental and molecular cor- 2. Apparatus
rection equations used in this method are correct and appropriate
for the mass spectrometer used and the sample matrix. a. Inductively coupled plasma-mass spectrometer: Available
2) Abundance sensitivity—Abundance sensitivity is the possi- from several manufacturers, this instrument includes a mass
bility that the low and high “wings” of any abundant mass peak spectrometer, detector, an ICP source, mass flow controllers for

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 3125 METALS BY INDUCTIVELY COUPLED PLASMA-MASS SPECTROMETRY - B. ICP-MS Method

Table 3125:5. Common Molecular Ion Interferences in ICP-MS1 a

Oxide interferences normally will be tiny and will affect method elements only
Element Measurement when oxide-producing elements are present at relatively high concentrations, or
Molecular Ion Mass Affected by Interference when the instrument is improperly tuned or maintained. Preferably monitor Ti
and Zr isotopes in soil, sediment, or solid waste samples, because these samples
Background molecular ions: could contain high levels of such interfering elements.
NH+ 15 — Reference
OH+ 17 — 1. U.S. Environmental Protection Agency. Determination of trace elements in
OH2+ 18 — ­waters and wastes by inductively coupled plasma-mass spectrometry; ­Method
C2+ 24 Mg
200.8. Cincinnati (OH): Environmental Monitoring Systems Laboratory,
CN+ 26 Mg
­Environmental Protection Agency; 1994.
CO+ 28 Si
N2+ 28 Si
N2H+ 29 Si
NO+ 30 —
NOH+ 31 P
O2+ 32 S regulating ICP gas flows, a peristaltic pump for introducing sam-
O2H+ 33 — ples, and a computerized data acquisition and instrument control
36
ArH+ 37 Cl system. An x-y autosampler also may be used with appropriate
38
ArH+ 39 K control software.
40
ArH+ 41 — b. Laboratory ware: Use pre-cleaned plastic laboratory ware
CO2+ 44 Ca
CO2+H 45 Sc for standard and sample preparation. Either tetrafluoroethylene
ArC+, ArO+ 52 Cr hexafluoropropylene-copolymer (FEP), polytetrafluoroethylene
ArN+ 54 Cr (PTFE), or perfluoroalkoxy (PFA) is preferred for standard
ArNH+ 55 Mn preparation and sample digestion, while high-density polyethylene
ArO+ 56 Fe (HDPE) and other dense, metal-free plastics may be acceptable for
ArH+ 57 Fe
40
Ar36Ar+ 76 Se
internal standards, known-addition solutions, etc. Check each new
40
Ar38Ar 78 Se lot of autosampler tubes for suitability, and preclean autosampler
40
Ar2+ 80 Se tubes and pipet tips if certificate of analysis is unavailable (see
Matrix molecular ions: Section 3010 C.2).
Bromide: c. Air-displacement pipets, sized 10 to 100 µL, 100 to 1000 µL,
  81BrH+ 82 Se and 1 to 10 mL.
  79BrO+ 95 Mo d. Analytical balance, accurate to 0.1 mg.
  81BrO+ 97 Mo
  81BrOH+ 98 Mo e. Sample-preparation apparatus, such as hot plates, microwave
  Ar81Br+ 121 Sb digesters, and heated sand baths. Any sample-preparation device
Chloride: could introduce trace levels of target analytes to the sample.
  35ClO+ 51 V f. Clean hood (optional), Class 100 (certified to contain less than
  35ClOH + 52 Cr 100 particles/m3), for sample preparation and manipulation. If
  37ClO+ 53 Cr
  37ClOH+ 54 Cr
possible, perform all sample manipulations, digestions, dilutions,
  Ar35Cl+ 75 As etc. in a certified Class 100 environment. Alternatively, handle
  Ar37Cl+ 77 Se samples in glove boxes, plastic fume hoods, or other environments
Sulfate: that minimize random contamination by trace metals.
  32SO+ 48 Ti
  32SOH+ 49 —
  34SO+ 50 V, Cr 3. Reagents
  34SOH+ 51 V
  SO2+, S2+ 64 Zn a. Acids: Use ultra-high-purity grade (or equivalent) acids
  Ar32S+ 72 Ge to prepare standards and process samples. Redistilled acids are
  Ar34S+ 74 Ge acceptable if each batch is demonstrated to be uncontaminated by
Phosphate: target analytes. Use extreme care when handling acids in the lab-
  PO+ 47 Ti
oratory to avoid contaminating them with trace levels of metals.
  POH+ 48 Ti
  PO2+ 63 Cu 1) Nitric acid (HNO3), conc (specific gravity 1.41).
  ArP+ 71 Ga 2) Nitric acid, 1 + 1—Add 500 mL conc HNO3 to 500 mL
Group I & II metals: reagent water.
  ArNa+ 63 Cu 3) Nitric acid, (v/v) 2%—Add 20 mL conc HNO3 to 100 mL
  ArK+ 79 Br reagent water; dilute to 1000 mL.
  ArCa+ 80 Se
Matrix oxidesa
4) Nitric acid, (v/v) 1%—Add 10 mL conc HNO3 to 100 mL
  TiO 62−66 Ni, Cu, Zn reagent water; dilute to 1000 mL.
  ZrO 106−112 Ag, Cd b. Reagent water: When preparing blanks, standards, and sam-
  MoO 108−116 Cd ples, use metal-free water that was prepared using the methods
  NbO 109 Ag listed in Section 1080, described below, or provided elsewhere (if
they have been proven effective). Use only high-purity water to
prepare samples and standards. Reagent water containing trace
amounts of analyte elements will skew results.

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 3125 METALS BY INDUCTIVELY COUPLED PLASMA-MASS SPECTROMETRY - B. ICP-MS Method

Table 3125:6. Elements, Masses, Abundances, and Correction Equations (Updated 2008)
Interference Calculation
Isotope Mass Abundance (if required)a Comments
Li (IS) 6 7.52 C 6 − 0.08131 × Li 7
Corrects for natural lithium in samples (I)
Be 9 100 C9
c 13 1.108 C 13 For ArC52 correction
Al 27 100 C 27
Ca 43 0.13 C 43 − 0.0004 × Sr88 Corrects for Sr2+b
Sc (IS) 45 100 C 45
V 51 99.76 C 51 − 3.1270 × ClO53 Corrects for variable chloride matrix (I) [not normally required in CCT Mode]
Cr 52 83.76 C 52 − 0.0900 × C13 Corrects for variable carbon content (P) [not normally required in CCT Mode]
ClO (Cr) 53 C 53 − 0.1140 × Cr52 CLO interference corrected for chromium (I)
Mn 55 100 C 55
Fe 56 91.52 C 56 CCT Mode only (ArO and CaO interferences in Standard Mode)
Co 59 100 C 59
Ni 60 26.16 C 60 − 0.00150 × Ca43 Corrects for CaO (P) [not normally required in CCT Mode]
Ni 62 3.66 C 62
Cu 63 69.09 C 63 Possibility of ArNa (P) in high sodium matrix (sea or brackish waters)
Cu 65 30.91 C 65
Zn 66 27.81 C 66
Zn 68 18.56 C 68 − 0.0153 × Ba135 Ba2+ interferes with Zn68
Ge (IS) 72 27.43 C 72 Possibility of FeO (P) interference in high iron matrix
As 75 100 C 75 − 3.1270 × ArCl77 Corrects for variable chloride matrix (I) Correction not required in CCT Mode (I)
ArCl (Se 77) 77 C 77 − 0.8484 × Se82 ArCl interference corrected for Se.
Se 78 23.61 C 78 CCT Mode only due to ArAr78 in Standard Mode
Se 82 8.84 C 82 − 1.0009 × Kr83 Corrects for krypton in argon (I)
Kr 83 11.55 C 83 Variable levels in argon
Sr 88 82.56 C 88 Forms Sr2+ easily
Mo 95 14.78 C 95 No isobaric correction required (unlike Mo98)
Mo 98 24 C 98 − 0.1307 × Ru101 Corrects for variable ruthenium content (I)
Ru 101 16.98 C 101 For Mo98 correction
Rh (IS) 103 100 C 103
Ag 107 51.35 C 107
Ag 109 48.65 C 109
Cd 111 12.86 C 111 − 0.0017 × Mo95 Corrects for MoO (P) [not normally required in CCT Mode]
Cd 114 28.81 C 114 − [0.0271 × Sn118] − Correction for MoO (P) and Sn (I) [MoO correction not normally required in
[0.0028 × Mo95] CCT Mode]
In (IS) 115 95.84 C 115 − 0.0142 × Sn118 Corrects for variable tin content (I)
Sn 118 24.01 C 118 For Cd114 and In115 correction
Sb 121 57.25 C 121
Sb 123 42.75 C 123 − 0.0449 × Te125 Corrects for variable tellurium content (I)
Te 125 6.99 C 125 For Sb123 correction
Ba 135 6.59 C 135
Tb (IS) 159 100 C 159
Ho (IS) 165 100 C 165 Ho2+ may interfere with Se82
Tl 203 29.5 C 203
Tl 205 70.5 C 205
Pb 206 25.15 C 206
Pb 207 21.11 C 207
Pb 208 52.38 C 208 × 1 × Pb206 + 1 × Pb207 Correction for variable lead abundance (I)
Bi (IS) 209 100 C 209
u 235 0.715 C 235
u 238 99.28 C 238
IS = internal standard element; I = isobaric correction.
a
All corrections should be verified and corrected for mass bias.
b
Doubly charged corrections may vary with plasma-tuning conditions and should be verified by the user before use.
Note: P represents correction that may vary with plasma-tuning conditions and should be verified by the user before use.

c. Stock, standard, and other required solutions: See Sections multi-element stock solutions (1000 mg/L) of the following ele-
3111 B.3j, 3111 D.3k, 3114 B.3j–n, and 3120 B.3d on preparing ments are required: aluminum, antimony, arsenic, barium, beryl-
standard stock solutions from elemental materials (pure metals, lium, cadmium, cerium, chromium, cobalt, copper, ­g­ermanium,
salts). Preferably, purchase high-purity, commercially prepared indium, lead, magnesium, manganese, molybdenum, nickel,
stock solutions and dilute to required concentrations. Single- or rhodium, scandium, selenium, s­ilver, strontium, terbium,

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 3125 METALS BY INDUCTIVELY COUPLED PLASMA-MASS SPECTROMETRY - B. ICP-MS Method

t­hallium, thorium, uranium, vanadium, and zinc. Prepare inter- standards may be used, and a 2-point blank and a midrange cali-
nal-standard and target-element stock solutions separately; they bration technique commonly used in ICP optical methods should
could be incompatible and cause precipitation or other solution also produce acceptable results. Calibrate all analytes using the
instability. selected concentrations. Prepare all calibration standards and
1) Internal standard stock solution—Germanium, indium, lith- blanks in a matrix of 2% nitric acid. Add internal standard mix
ium, scandium, and thorium are suggested as internal standards. to all calibration standards to provide appropriate count rates for
The following masses are monitored: 72Ge, 115In, 6Li, 45Sc, and interference correction. Note: Add the same ratio of internal stan-
232
Th. Add enough internal standard to all samples, standards, and dard mix to all standards and blanks used in this method.
quality control (QC) samples to give a suitable counts per sec- 4) Method blank (MB)—A method blank (also known as reagent
ond (cps) signal and stability (100 000 to 300 000 cps for most blank) is a portion of reagent water (¶ b above) treated exactly as
internal standards). Minimize dilution-related errors by using an a sample, including exposure to all equipment, glassware, proce-
appropriately high concentration of internal standard mix solu- dures, and reagents. It is used to assess whether analytes or inter-
tion. Maintain volume ratio for all internal standard additions. ferences are present in the analytical process or system. No MB
Prepare internal standard mix as follows: Prepare a nominal should contain a warning level of any analyte of interest (based
50-mg/L solution of 6Li by dissolving 0.15 g 6Li2CO3 [isotopically on the end user’s requirements). Undertake immediate corrective
pure, (i.e., 95% or greater purity)] in a minimal amount of 1:1 action for MB measurements above the minimum reporting level
HNO3. Pipet 5.0 mL 1000-mg/L germanium, indium, scandium, (see Section 3020 B.5). Include at least one MB with each batch
and thorium standards into the lithium solution, dilute resulting of samples prepared. For dissolved samples, take reagent water
solution to 500.0 mL, and mix thoroughly. The resultant concen- through same filtration and preservation processes used for sam-
tration of Ge, In, Sc, and Th will be 10 mg/L. Determine the inter- ples. For samples requiring digestion, process reagent water with
nal standard concentrations required to achieve acceptable levels the same digestion techniques as samples. Add internal standard
of precision, and dilute the internal standard stock accordingly. mix to method blank.
Other internal standards, such as bismuth, holmium, rhodium, 5) Calibration verification standard—Prepare a midrange stan-
terbium, and yttrium, may also be used in this method. Ensure dard using a different source than that used for the calibration
that the internal standard mix used is stable and that there are no standards, in 2% HNO3, with equivalent addition of internal stan-
undesired interactions among elements. dard.
All new sample matrices should be screened for internal stan- 6) Calibration verification blank—Use 2% HNO3, the same
dard elements before analysis. Analyzing a few representative solution as the zero calibration standard.
samples for internal standards should be sufficient. Analyze sam- 7) Laboratory-fortified blank (LFB)—The laboratory-fortified
ples as received or as digested (before adding internal standard), blank (also known as a blank spike) is a method blank that has
then add internal standard mix and re-analyze. Monitor counts been fortified with a known concentration of analyte. It is used
at the internal standard masses. If the as-received or as-digested to evaluate ongoing laboratory performance and analyte recovery
samples show appreciable detector counts (10% or higher of sam- in a clean matrix. Prepare fortified concentrations approximating
ples with added internal standard), dilute sample or use another the midpoint of the calibration curve (50 ng/mL) or lower with
internal standard. If the response of a sample containing the inter- stock solutions prepared from a different source than that used to
nal standard is not within 70% to 125% of the response for a cal- develop working standards. Calculate percent recovery, plot con-
ibration blank with the internal standard, either dilute the sample trol charts, and determine control limits for these measurements.
before analysis or use another internal standard. During actual Ensure that the LFB meets the method’s performance criteria
analysis, monitor internal standard masses and note all internal when such criteria are specified. Establish corrective actions to be
standard recoveries that are more than 125% of the internal stan- taken in case the LFB does not satisfy acceptance criteria. Include
dard response in the calibration blank. Interpret results for these at least one LFB with each batch of samples prepared. This stan-
samples with caution. dard, sometimes also called a laboratory control sample (LCS), is
The internal standard mix may be added to blanks, standards, used to validate digestion techniques and known-addition levels.
and samples via a y-shaped connector after the peristaltic pump to 8) Reference materials—Use externally prepared reference
mix it with the sample stream during sample introduction. material, preferably from National Institute of Standards and
2) Instrument optimization/tuning solution—containing beryl- Technology1643 series or equivalent.
lium, cadmium, cobalt, copper, germanium, indium, rhodium, 9) Known-addition solution for samples—Add stock standard
scandium, terbium, thallium, (for sensitivity and stability evalua- to sample so the volume change is less than 5%. In the absence
tion), barium (for doubly-charged evaluation), cerium (for oxide of information on analyte levels in the sample, prepare known
evaluation), magnesium (mass calibration check), and lead (mass additions at around 50 µg/L or lower. If analyte concentration
calibration check). Prepare this solution in 2% HNO3. This mix levels are known, add at 50% to 200% of the sample levels. For
includes all common elements used to optimize and tune various samples undergoing digestion, make additions before digestion.
ICP-MS operating parameters. It may be possible to use fewer For dissolved metals determinations, make additions after filtra-
elements in this solution, depending on the instrument manufac- tion, preferably immediately before analysis.
turer’s recommendations. 10) Low-level standards—Use both a 0.3- and a 1.0-µg/L stan-
3) Calibration standards—A 5-standard calibration is recom- dard when expected analyte concentration is less than 5 µg/L.
mended, from 0 to 100 µg/L (performance data for the method Prepare both standards in 2% nitric acid.
were obtained with these concentrations). Other calibration reg- Prepare volumetrically a mixed standard containing the method
imens are acceptable if the full suite of quality assurance sam- analytes at desired concentration(s) (0.30 µg/L, 1.0 µg/L, or
ples and standards is run to validate any method changes. Fewer both). Prepare weekly in 100-mL quantities.

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d. Argon: Use a prepurified grade of argon unless it can be Table 3125:7. Suggested Analytical Run Sequence
demonstrated that other grades can be used successfully. Prepu- Sample Type Comments
rified argon is usually necessary because technical argon often
contains significant levels of impurities (e.g., carbon and kryp- Tuning/optimization standard Check mass calibration and
ton). 82Kr interferes with the determination of 82Se. Monitor 83Kr resolution
at all times. Tuning/optimization standard Optimize instrument for
maximum rhodium counts
while keeping oxides,
4. Procedures double-charged ions,
and background within
a. Sample preparation: See Sections 3010 and 3020 for gen- instrument specifications
eral guidance and additional specific requirements on sampling Rinse —
and quality control. See Section 3030 E for the recommended Reagent blank Check for contamination
sample-digestion technique for all analytes except silver and Reagent blank Calibration standard blank
antimony. Use the method in Section 3030 F for silver and anti- 5 µg/L standard —
mony, paying special attention to chloride ion interferences and 10 µg/L standard —
20 µg/L standard —
using all applicable elemental corrections. Alternative diges-
50 µg/L standard —
tion techniques and more guidance on sample preparation are 100 µg/L standard —
available.3,4 Rinse Check for memory
Ideally, use a clean environment when handling, manipulating, Initial calibration verification, 50 µg/L Check for calibration accuracy
or preparing samples. Preferably perform all sample manipula- Initial calibration blank Check for memory
tions in a Class 100 clean hood or room to minimize potential 0.30-µg/L standard Low-level calibration
contamination artifacts in digested or filtered samples. verification
b. Instrument operating conditions: Follow manufacturer’s 1.0-µg/L standard Low-level calibration
standard operating procedures for initialization, mass calibration, verification
External reference material NIST 1643c or equivalent
gas flow optimization, and other instrument operating conditions. Continuing calibration verification Check for calibration stability
Maintain complete, detailed information on the instrument’s Continuing blank calibration Check for memory
operating status whenever it is used. Project sample method blank Check for contamination
c. Analytical run sequence: Table 3125:7 outlines a suggested Project sample laboratory-fortified Check for spike recovery
analytical run sequence, including tuning and optimizing the blank
instrument, checking reagent blanks, calibrating the instrument, Project sample 1–4 Check for possible
verifying the calibration, analyzing samples, and analyzing qual- interferences
ity control samples and blanks. Project sample 5 —
Project sample 5 with known addition Check for spike recovery
d. Instrument tuning and optimization: Follow manufacturer’s
instructions for optimizing instrument performance. The most Project sample 5 duplicate with known Check for reproducibility
important optimization criteria include nebulizer gas flows, addition
detector and lens voltages, radio-frequency forward power, and Continuing calibration verification Check for calibration stability
mass calibration. Periodically check mass calibration and instru- (every 10 samples)
ment resolution. Ideally, optimize the instrument to minimize the Continuing calibration blank Check for memory
formation of oxide and doubly charged species. Measure CeO+: (every 10 samples)
Ce+ and Ba2+:Ba+ ratios to monitor the formation of oxide and
doubly charged species, respectively. Both ratios should meet the
manufacturer’s criteria before instrument calibration. Monitor acceptable. If analyte concentrations are less than 5 µg/L, verify
background counts at mass 220 after optimization, and compare low-level calibration by using a standard at 40% to 50% of the
with manufacturer’s criteria. (See Table 3125:8 for a summary of highest low-level standard.
method performance criteria related to optimization and tuning, f. Sample analysis: Ensure that all vessels and reagents are
calibration, and analytical performance.) uncontaminated. During the analytical run, include quality-con-
e. Instrument calibration: After optimization and tuning, cal- trol analyses according to schedule of Table 3125:9 or follow
ibrate the ICP-MS using an appropriate range of calibration project-specific QA/QC protocols.
standards. Use appropriate regression techniques to determine Internal standard recoveries must be between 70% and 125% of
calibration responses for each analyte. For acceptable calibra- internal standard response in the laboratory-fortified blank; oth-
tions, the regression curves’ correlation coefficients are ideally erwise, dilute sample, add internal standard mix, and re-analyze.
0.995 or greater. Make known-addition analyses for each matrix in a digestion
Immediately after calibration, run initial calibration verifi- or filtration batch.
cation standard, 3125 B.3c5; acceptance criteria are ±10% of
known analyte concentration. Next, run initial calibration veri- 5. Calculations and Corrections
fication blank, 3125 B.3c6; acceptance criteria are ideally ± the
absolute value of the instrument detection limit for each analyte, Configure instrument software to report internal-standard-cor-
but in practice, the absolute value of the laboratory reporting rected results. Water sample results should be reported in micro-
limit or the laboratory method detection limit for each analyte is grams per liter. Report appropriate number of significant figures.

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Table 3125:8. Summary of Performance Criteria where:

RCorr = corrected result (µg/kg),
Performance Characteristic Criteria
RUncorr = uncorrected elemental result (µg/L),
Mass resolution Manufacturer’s specification V = volume of digestate after digestion (L),
Mass calibration Manufacturer’s specification W = mass of the wet sample (kg), and
Ba2+/Ba+ Manufacturer’s specification % TS = percent total solids determined in the sample.
CeO/Ce Manufacturer’s specification
Background counts at mass 220 Manufacturer’s specification b. Compensation for interferences: use instrument software to
Correlation coefficient >0.995 correct for previously listed interferences. See Table 3125:6 for a
Calibration blanks < Reporting limit
list of the most common molecular ion interferences.
Calibration verification standards ±10% of true value
Laboratory fortified blank ±30% of true value c. Data reporting: Establish appropriate reporting limits for
(control sample) method analytes based on IDLs and the laboratory blank. For reg-
Precision ±20% relative percent difference ulatory programs, ensure that reporting limits for method analytes
for lab duplicates are a factor of three below relevant regulatory criteria whenever
Known-addition recovery 75%–125% possible.
0.3 and 1.0 µg/L standards Dependent on data quality If method blank contamination is typically random, sporadic,
objectives or otherwise not statistically controllable, do not correct results
Reference materials Dependent on data quality for the method blank. Consider correcting blank results only if
objectives it can be demonstrated that the blank’s analyte concentration
Internal standard response 70%–125% of response in is within statistical control over a period of months. Report all
calibration blank with known method blank data explicitly in a manner identical to sample-re-
addition porting procedures.
d. Documentation: Maintain documentation for the following
(where applicable): instrument tuning, mass calibration, calibra-
a. Correction for dilutions and solids: Correct all dilution tion verification, analyses of blanks (method, field, calibration,
results, and raise the related reporting limits accordingly: and equipment blanks), IDL and MDL studies, analyses of sam-
ples and duplicates with known additions, laboratory and field
duplicate information, serial dilutions, internal standard recover-
R ×V
RCorr = Uncorr ies, and any relevant quality control charts.
(Vs /V ) Also, maintain all raw data generated in support of the method,
and keep them available for review.5
where:
RCorr = diluted corrected results (µg/L), 6. Method Performance
RUncorr = uncorrected elemental results (µg/L),
V = volume of digestate after digestion (L), and
Table 3125:3 presents IDL data generated by this method.
V = volume of undiluted sample (L). This represents optimal instrument detection capabilities, not
recommended method detection or reporting limits. Tables
Use Method 2540 B to determine total solids in solid samples, 3125:1, 3125:2, 3125:10, 3125:11, and 3125:12 contain sin-
and report results as micrograms per kilogram, dry weight. Cor- gle-laboratory, single-operator, single-instrument performance
rect all results for solids content of solid samples. Use the fol- data generated by this method for calibration verification stan-
lowing equation to correct solid or sediment sample results for dards, low-level standards, and known-addition recoveries for
dilution during digestion and moisture content: freshwater matrices, as well as data showing standard and CCT
performance data for elements usually affected by polyatomic
RUncorr × V interferences (Tables 3125:1 and 2). Section 3125 performance
RCorr = data for some analytes are currently unavailable; however, per-
W × % TS /100

Table 3125:9. Quality Control Analyses for ICP–MS Method

Analysis Frequency Acceptance Criteria
Reference material [3125 B.3c9)] Greater of: once per sample batch, or 5% Dependent on data quality objectives
Preparatory/method blank [3125 B.3c4)] Greater of: once per sample batch, or 5% ± Absolute value of instrument detection limit;
absolute value of laboratory reporting limit or
MDL is acceptable
Laboratory-fortified blank [3125 B.3c7)] Greater of: once per sample batch, or 5% ±30% of true value
Duplicate known-addition samples Greater of: once per sample batch, or 5% ±20% relative percent difference
Continuing calibration verification standards 10% ±10% of known concentration
[3125 B.3c5)]
Continuing calibration verification 10% ± Absolute value of instrument detection limit;
blank [3125 B.3c6)] absolute value of laboratory reporting limit or
MDL is acceptable

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 3125 METALS BY INDUCTIVELY COUPLED PLASMA-MASS SPECTROMETRY - B. ICP-MS Method

Table 3125:10. Method Performance with Calibration Verification Standardsa

Continuing Calibration Verification Standard (N = 44) Initial Calibration Verification Standard (N = 12)
Mean Standard Relative Standard Mean Standard Relative Standard
Recovery Mean Deviation Deviation Recovery Mean Deviation Deviation
Element Mass % µg/L µg/L % % (µg/L) (µg/L) (%)
Be 9 98.71 49.35 3.43 6.94 100.06 50.03 1.90 3.80
Al 27 99.62 49.81 2.99 6.01 98.42 49.21 1.69 3.44
V 51 100.97 50.48 1.36 2.68 99.91 49.96 1.23 2.47
Cr 52 101.39 50.70 1.86 3.66 99.94 49.97 1.47 2.95
Cr 53 100.68 50.34 1.91 3.79 99.13 49.56 1.44 2.90
Mn 55 101.20 50.60 1.98 3.91 99.48 49.74 1.40 2.82
Co 59 101.67 50.83 2.44 4.79 99.44 49.72 1.61 3.24
Ni 60 99.97 49.99 2.14 4.28 97.98 48.99 1.70 3.47
Ni 62 99.79 49.89 2.09 4.18 97.57 48.79 1.32 2.71
Cu 63 100.51 50.25 2.19 4.36 97.87 48.93 1.63 3.33
Cu 65 100.39 50.19 2.26 4.51 98.34 49.17 1.58 3.20
Zn 66 101.07 50.53 1.93 3.82 98.75 49.38 0.87 1.76
Zn 68 100.42 50.21 1.89 3.77 97.75 48.87 0.50 1.02
As 75 100.76 50.38 1.15 2.28 98.83 49.41 0.89 1.80
Se 77 101.71 50.85 1.43 2.81 99.54 49.77 1.01 2.03
Se 82 101.97 50.98 1.50 2.95 99.76 49.88 0.94 1.89
A
g 107 101.50 50.75 1.68 3.30 99.27 49.63 1.17 2.36
A
g 109 101.65 50.83 1.68 3.31 99.66 49.83 1.54 3.08
Cd 111 100.92 50.46 1.94 3.84 98.61 49.30 1.36 2.77
Cd 114 100.90 50.45 2.07 4.10 99.20 49.60 1.41 2.84
Sb 121 100.14 50.07 2.39 4.77 99.38 49.69 1.38 2.78
Sb 123 99.98 49.99 2.48 4.97 99.09 49.54 1.34 2.71
Tl 203 101.36 50.68 1.64 3.23 100.05 50.02 1.01 2.01
Tl 205 102.40 51.20 1.93 3.78 101.23 50.62 1.45 2.87
Pb 208 101.21 50.61 1.65 3.25 99.33 49.67 0.84 1.69
U 238 101.54 50.77 1.93 3.80 99.80 49.90 1.36 2.72
a
Single-laboratory, single-operator, single-instrument data, determined using a 50-µg/L standard prepared from sources independent of calibration standard source. Data ac-
quired January-November 1996 during actual sample determinations. Performance of continuing calibration verification standards at different levels may vary. Perkin-Elmer
Elan 6000 ICP-MS used for determination.

formance data for similar ICP-MS methods are available in the Bibliography
literature.1,4
Gray AL. A plasma source for mass analysis. Proc Soc Anal Chem.
References 1974;11:182–183.
Hayhurst AN, Telford NR. Mass spectrometric sampling of ions from
atmospheric pressure flames. I. Characteristics and calibration of the
1. U.S. Environmental Protection Agency. Determination of trace ele-
sampling system. Combust Flame. 1977;28:67–80.
ments in waters and wastes by inductively coupled plasma-mass
Houk RS, Fassel VA, Flesch GD, Svec HJ, Gray AL, Taylor CE. Induc-
spectrometry; Method 200.8. Cincinnati (OH): Environmental Moni-
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the determination of the method detection limit, rev. 1.11. 40 CFR Douglas DJ, French JB. Elemental analysis with a microwave-
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plasma mass spectrometry. Washington DC: Office of Water, U.S. Houk RS. Mass spectrometry of inductively coupled plasmas. Anal
Environmental Protection Agency; 1995. Chem. 1986;58(1):97A–105A.
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umentation and evaluation of trace metals data collected for Clean ric detection for multielement flow injection analysis and elemental
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 3125 METALS BY INDUCTIVELY COUPLED PLASMA-MASS SPECTROMETRY - B. ICP-MS Method

Table 3125:11. Method Performance for Recovery of Known Addition in Natural Watersa
Total Recoverable Metalsb Dissolved Metalsc
Mean Recovery Relative Standard Deviation Mean Recovery Relative Standard Deviation
Element Mass (%) (%) (%) (%)
Be 9 89.09 5.77 — —
V 51 87.00 8.82 — —
Cr 52 87.33 8.42 88.38 6.43
Cr 53 86.93 7.90 88.52 5.95
Mn 55 91.81 10.12 — —
Co 59 87.67 8.92 — —
Ni 60 85.07 8.42 89.31 5.70
Ni 62 84.67 8.21 89.00 5.82
Cu 63 84.13 8.46 88.55 8.33
Cu 65 84.37 8.05 88.26 7.80
Zn 66 86.14 23.01 95.59 13.81
Zn 68 81.95 20.31 91.94 13.27
As 75 90.43 4.46 97.30 8.84
Se 77 83.09 4.76 105.36 10.80
Se 82 83.42 4.73 105.36 10.75
Ag 107 — — 91.98 5.06
A
g 109 — — 92.25 4.96
Cd 111 91.37 5.47 96.91 6.03
Cd 114 91.47 6.04 97.03 5.42
Sb 121 94.40 5.24 — —
Sb 123 94.56 5.36 — —
Tl 203 97.24 5.42 — —
Tl 205 98.14 6.21 — —
Pb 208 96.09 7.08 100.69 7.28
a
Single-laboratory, single-operator, single-instrument data. Samples were Washington State surface waters from various locations. Data acquired January-November 1996
during actual sample determinations. Performance of known additions at different levels may vary. Perkin-Elmer Elan 6000 ICP-MS used for determination.
b
Known-addition level 20 µg/L. Additions made before preparation according to Section 3030 E (modified by clean-hood digestion in TFE beakers). N = 20.
c
Known-addition level for Cd and Pb 1 µg/L; for other analytes 10 µg/L. Additions made after filtration through 1:1 HNO3 precleaned 0.45-µm filters. N = 28.

Table 3125:12. Method Performance with Calibration Verification Standardsa

1.0-µg/L Standard 0.3-µg/L Standard
Mean Standard Relative Standard Mean Standard Relative Standard
Recovery Mean Deviation Deviation Recovery Mean Deviation Deviation
Element Mass (%) (µg/L) (µg/L) (%) (%) (µg/L) (µg/L) (%)
Be 9 97 0.97 0.06 6.24 95 0.284 0.03 12.11
Al 27 121 1.21 0.32 26.49 196 0.588 0.44 74.30
V 51 104 1.04 0.06 5.83 111 0.332 0.10 28.96
Cr 52 119 1.19 0.34 28.62 163 0.490 0.37 75.90
Cr 53 102 1.02 0.36 35.54 113 0.338 0.32 93.70
Mn 55 103 1.03 0.07 6.55 110 0.329 0.08 25.64
Co 59 103 1.03 0.07 6.42 102 0.307 0.04 12.53
Ni 60 101 1.01 0.05 5.24 107 0.321 0.05 14.14
Ni 62 102 1.02 0.06 5.42 109 0.326 0.05 15.94
Cu 63 107 1.07 0.09 8.78 118 0.355 0.06 18.29
Cu 65 107 1.07 0.10 9.05 117 0.352 0.06 17.69
Zn 66 117 1.17 0.51 43.52 182 0.547 0.68 124.13
Zn 68 116 1.16 0.50 42.90 179 0.537 0.66 122.12
As 75 97 0.97 0.05 5.23 101 0.302 0.06 18.29
Se 77 89 0.89 0.08 8.72 88 0.265 0.08 29.07
Se 82 92 0.92 0.14 15.50 106 0.317 0.14 43.91
Ag 107 101 1.01 0.05 4.53 94 0.282 0.04 15.74
Ag 109 103 1.03 0.07 6.57 92 0.277 0.04 13.68
Cd 111 98 0.98 0.04 3.80 96 0.288 0.03 8.74
Cd 114 100 1.00 0.03 3.39 98 0.293 0.03 8.70
Sb 121 94 0.94 0.05 5.28 93 0.280 0.06 21.89
Sb 123 94 0.94 0.05 5.36 93 0.278 0.06 22.39
Tl 203 101 1.01 0.04 3.57 98 0.294 0.03 11.89
Tl 205 104 1.04 0.05 5.15 100 0.300 0.03 10.43
Pb 208 104 1.04 0.04 3.65 104 0.312 0.03 11.13
U 238 106 1.06 0.05 4.64 102 0.307 0.03 9.92
a
Single-laboratory, single-operator, single-instrument data. N = 24 for both standards.

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Published Online: August 27, 2018

Revised: May 21, 2020
https://doi.org/10.2105/SMWW.2882.048 11