## 3125 METALS BY INDUCTIVELY COUPLED PLASMA–MASS SPECTROMETRY*

3125 A. Introduction

1. General Discussion



### This method is designed to determine trace metals and metalloids in surface, ground, and drinking waters via inductively coupled plasma mass spectrometry (ICP–MS). Although best suited for ambient or pristine freshwater matrices, this method can also be used to analyze wastewater, soils, sediments, sludge, and biological samples after appropriate digestion followed by dilution and/or cleanup to reduce matrix effects to a manageable level. 1,2 

### Various cleanup techniques are available to reduce matrix interferences and/or concentrate analytes of interest. 3–7



### For many analytes, the instrument detection limits (IDLs) are between 1 and 100 ng/L. The quadrupole-based ICP–MS may include collision cell technology (CCT) and/or dynamic reactioncell (DRC), which remove the need for mathematical interference correction for many elements. Additional data (Tables 3125:I and 3125:II) demonstrate the performance for elements seriously affected by polyatomic interferences. 8,9



### The method is intended to be performance-based, so the elemental analyte list can be extended, new “clean” preparation

techniques can be implemented, and other appropriate modifications can be made as technology evolves. Any modifications to the base method must be validated via suitable quality control standards. More sources of information on quality assurance and other aspects of ICP–MS analysis of metals are available. 10–12



### Ideally, the analysts who use this method will have experience using ICP–MS, interpreting spectral and matrix interferences, and implementing corrective procedures. Before generating data, analysts should demonstrate their proficiency in this method by successfully analyzing a performance evaluation sample for each matrix type.

2. References

1. M ONTASER , A. & D.W. G OLIGHTLY , EDS . 1992. Inductively CoupledPlasmas in Analytical Atomic Spectrometry, 2nd ed. VCH Publishers, Inc., New York, N.Y. 2. D ATE , A.R. & A.L. GRAY . 1989. Applications of Inductively Coupled Plasma Mass Spectrometry. Blackie & Son, Ltd., Glasgow, U.K. 3. M CLAREN , J.W., A.P. M YKYTIUK , S.N. WILLIE & S.S. B ERMAN . 1985. Determination of trace metals in seawater by inductively coupled * Approved by Standard Methods Committee, 2009. Joint Task Group: Robert Henry (chair), Christopher J. Baggett, Alois F. Clary, William R. Kammin, Gregg Oelker, Cindy A. Ziernicki.

TABLE 3125:I. M ETHOD PERFORMANCE WITH C ALIBRATION V ERIFICATION S TANDARDS *†

Element Mass Mean Recovery % Mean ng/mL SD ng/mL RSD %

V 51 100.00 200.0 9.25 4.62 V CCT 51 100.44 200.9 7.30 3.63 Cr 52 99.56 199.1 9.39 4.72 Cr CCT 52 100.56 201.1 7.16 3.56 Mn 55 101.36 1014 54.09 5.34 Mn CCT 55 98.28 982.8 31.95 3.25 Fe 56 101.84 10184 566.43 5.56 Fe CCT 56 100.25 10025 336.29 3.35 Co 59 101.58 20.32 0.89 4.38 Co CCT 59 101.67 20.33 0.64 3.15 Ni 60 101.08 202.2 9.06 4.48 Ni CCT 60 101.90 203.8 6.61 3.24 Cu 63 101.76 1018 62.46 6.14 Cu CCT 63 105.63 1056 36.79 3.48 Cu 65 102.12 1021 56.06 5.49 Zn 66 100.52 1005 47.63 4.74 Zn CCT 66 99.51 995.1 33.94 3.41 As 75 99.54 19.91 1.02 5.14 As CCT 75 98.24 19.65 0.78 3.99 Se 78 102.77 20.55 1.04 5.07 Se CCT 78 104.78 20.96 1.73 8.26
* Single-laboratory, single-operator data acquired 12-2005 using Thermo Electron X Series in Standard and CCT-KED modes. † Continuing Calibration Verification Standard (N  28) TABLE 3125:II. M ETHOD PERFORMANCE WITH S TANDARD REFERENCE WATER *†

Element Mass Mean Recovery % Mean ng/mL SD ng/mL RSD %

V 51 95.49 12.40 0.62 5.01 V CCT 51 101.60 13.20 0.32 2.39 Cr 52 93.34 36.03 0.80 2.21 Cr CCT 52 95.31 36.79 0.89 2.42 Mn 55 99.09 120.40 2.25 1.87 Mn CCT 55 96.99 117.8 2.18 1.85 Fe 56 110.45 37.89 4.32 11.41 Fe CCT 56 102.20 35.06 1.78 5.09 Co 59 98.43 19.96 0.32 1.62 Co CCT 59 99.22 20.12 0.36 1.79 Ni 60 98.78 27.06 0.68 2.51 Ni CCT 60 100.69 27.59 0.50 1.80 Cu† 63 115.36 98.29 3.68 3.74 Cu CCT‡ 63 122.91 104.7 2.81 2.68 Cu‡ 65 118.83 101.2 2.84 2.80 Zn 66 95.88 51.01 1.36 2.67 Zn CCT 66 97.64 51.95 1.91 3.68 As 75 98.61 26.30 0.48 1.81 As CCT 75 98.38 26.24 0.59 2.26 Se 78 95.83 21.04 0.45 2.15 Se CCT 78 97.58 21.43 1.86 8.66
* Single-laboratory, single-operator data acquired 12-2005 using Thermo Electron X Series in Standard and CCT-KED modes. † NIST 1640 (N  7) ‡ Copper contamination

1plasma mass spectrometry with preconcentration on silica-immobilized 8-hydroxyquinoline. Anal. Chem. 57:2907. 4. B URBA , P. & P.G. WILLMER . 1987. Multielement preconcentrationfor atomic spectroscopy by sorption of dithiocarbamate metal complexes (e.g., HMDC) on cellulose collectors. Fresenius Z. Anal. Chem. 329:539. 5. WANG , X. & R.M. B ARNES . 1989. Chelating resins for on-line flow injection preconcentration with inductively coupled plasma atomic emission spectroscopy. J. Anal. Atom. Spectrom. 4:509. 6. S IRIRAKS , A., H.M. KINGSTON & J.M. RIVIELLO . 1990. Chelation ionchromatography as a method for trace elemental analysis in complex environmental and biological samples. Anal. Chem. 62:1185. 7. PUGET S OUND WATER Q UALITY AUTHORITY . 1996. Recommended Guidelines for Measuring Metals in Puget Sound Marine Water, Sediment and Tissue Samples. Appendix D: Alternate Methods for the Analysis of Marine Water Samples. Puget Sound Water Quality Authority, Olympia, Wash. 8. NELMS , S., ED . 2005. Inductively Coupled Plasma Mass Spectrometry Handbook. Blackwell Science, Cambridge, Mass. 9. B ECKER , J.S. 2008. Inorganic Mass Spectrometry: Principles and Applications. Wiley Interscience, Malden, Mass. 10. U.S. ENVIRONMENTAL PROTECTION A GENCY . 1994. Determination of trace elements in waters and wastes by inductively coupled plasma– mass spectrometry, Method 200.8. U.S. Environmental ProtectionAgency, Environmental Monitoring Systems Laboratory, Cincinnati, Ohio. 11. L ONGBOTTOM , J.E., T.D. M ARTIN , K.W. EDGELL , S.E. L ONG , M.R. PLANTZ & B.E. WARDEN . 1994. Determination of trace elements inwater by inductively coupled plasma–mass spectrometry: collaborative study. J. AOAC Internat. 77:1004. 12. U.S. ENVIRONMENTAL PROTECTION A GENCY . 1995. Method 1638: Determination of trace elements in ambient waters by inductively coupled plasma–mass spectrometry. U.S. Environmental Protection Agency, Off. Water, Washington, D.C.



## 3125 B. I nductively Coupled Plasma Mass Spectrometry (ICP–MS) Method

1. General Discussion



### a. Principle: In this method, analysts introduce sample material to an argon-based, high-temperature radio-frequency plasma, usually via pneumatic nebulization. As energy transfersfrom the plasma to the sample stream, the target element desolves, atomizes, and ionizes. The resulting ions are extracted from the plasma through a differential vacuum interface and separated based on their mass-to-charge (m/z) ratio by a mass spectrometer. Typically, either a quadrupole (with or withoutCCT or DRC) or magnetic sector (high-resolution) mass spectrometer is used. An electron multiplier detector counts the separated ions, and a computer-based data-management system processes the resulting information.

b. Applicable elements and analytical limits: This method hasbeen demonstrated to be suitable for aluminum, antimony, arsenic, barium, beryllium, cadmium, chromium, cobalt, copper,lead, manganese, molybdenum, nickel, selenium, silver, strontium, thallium, uranium, vanadium, and zinc (see Table 3125: III). It is also acceptable for other elemental analytes as long asthe same quality assurance practices are followed, with documented acceptance limits.

Before implementing the method, determine the instrument detection limit (IDL) and method detection limit (MDL) for all analytes (see Section 1030C). Typical IDLs for method analytes are presented in Table 3125:III. 1,2



### Determining the MDL for each element is critical when analyzing complex matrices, such as seawater, brines, and industrial effluents. In these cases, the MDL typically will be higher than the IDL because of background levels of analytes introducedduring sample preparation, as well as laboratory-derived contamination and matrix-based interferences. Determine both IDL and MDL when first implementing this method, and then repeat yearly or whenever the instrument configuration changes or major maintenance occurs, whichever happens first.

Also, determine the linear dynamic range (LDR) for all method analytes, including multi-element mixtures (to account for possible inter-element effects). LDR is the maximum analyte concentration above the highest calibration point at which the analyte response is within 10% of its theoretical response. When determining LDRs, avoid using unnecessarily high analyteconcentrations because they might damage the detector. Determine LDR when first implementing this method, and then repeat yearly.

c. Interferences: ICP–MS is subject to several types of interferences, including the following:

1) Isobars: Isobars are isotopes of different elements that form ions with the same nominal atomic mass units/charge number(m/z) ratio that cannot be resolved by a quadrupole or highresolution mass spectrometer. Typically, ICP–MS operatingsoftware includes all known isobaric interferences and will perform the necessary calculations automatically (see Table 3125: IV.) Monitor 83 

### Kr, 99 

### Ru, 118 

### Sn, and 125 

### Te to correct for isobaric interference caused by 82 

### Kr on 82 

### Se, by 98 

### Ru on 98 

### Mo, by 114 

### Sn

on 114 

### Cd, by 115 

### Sn on 115 

### In, and by 123 

### Te on 123 

### Sb. Monitor ArCl at mass 77 to estimate chloride interferences. Verify that all elemental and molecular correction equations used in this method are correct and appropriate for the mass spectrometer used and the sample matrix.

2) Abundance sensitivity: Abundance sensitivity is the possibility that the low and high “wings” of any abundant mass peak will contribute to or obscure adjacent masses. Adjust the mass spectrometer resolution and quadrupole pole bias to minimize these interferences.

3) Polyatomics: Polyatomics are (molecular) ion interferences caused by ions with more than one atom that have the same nominal m/z ratio as the isotope of interest. Most of the common molecular ion interferences have been identified (see Table 3125:V). Because of the severity of chloride ion interference onimportant analytes, particularly vanadium and arsenic, hydrochloric acid is not recommended for use in ICP–MS sample preparation. Because most environmental samples contain some chloride ion, analysts must use chloride-correction equations for affected masses. Collision cell technology and dynamic reaction INDUCTIVELY COUPLED PLASMA–MASS SPECTROMETRY (3125)/ICP–MS Method

2

### cell effectively reduce most polyatomic species to analyticallynegligible levels in quadrupole-based ICP–MS systems, sometimes removing the need for complex correction equations. Ahigh-resolution ICP–MS resolves many—but not all—interferences caused by polyatomic ions. Polyatomic interferences are strongly influenced by instrument design and plasma operatingconditions; they sometimes can be reduced by carefully adjusting nebulizer gas flow and other instrument operating parameters.

4) Doubly-charged: Some elements (e.g., barium and strontium) form significant levels of M 2  

### ions under normal plasma conditions. The M 2  

### ions occur in the mass spectrum at M/2 and, in the case of Ba and Sr, will interfere with some isotopes of zinc and calcium, respectively.

5) Physical interferences: These include differences in viscosity, surface tension, and dissolved solids between samples andcalibration standards. To minimize these effects, analytical samples should not contain more than 0.5% of dissolved solids. Dilute water and wastewater samples with higher dissolved solids levels before analyzing them. Use internal standards to correct for physical interferences, provided that their analytical behavior is comparable to the elements being determined.

Table 3125:IV.B includes information on each isotope and cautions on using correction equations. Quadrupole ICP–MS with CCT or DRC is recommended for all analytes, exceptperhaps beryllium (due to lower sensitivity), because it eliminates many of the equations typically needed in the standard operating mode.

6) Memory interferences: These occur when analytes from a previous sample or standard are measured in the current sample. Use a long enough rinse (flush) between samples to minimize such interferences. Persistent memory interferences may indicate problems in the sample-introduction system. Severe memory interferences may require analysts to disassemble and clean the entire sample-introduction system, including the plasma torch and the sampler and skimmer cones.

7) Ionization interferences: These result when moderate (0.1% to 1%) amounts of a matrix ion change the analyte signal. This TABLE 3125:III. RECOMMENDED ANALYTE M ASSES , INSTRUMENT D ETECTION LIMITS (IDL), AND INTERNAL S TANDARDS

Element Analytical Mass IDL*


g/L Recommended Internal Standard

Be 9 0.025 Li Al 27 0.03 Sc V 51 0.02 Sc Cr 52 0.04 Sc Cr 53 0.03 Sc Mn 55 0.002 Sc Co 59 0.002 Sc Ni 60 0.004 Sc Ni 62 0.025 Sc Cu 63 0.003 Sc Cu 65 0.004 Sc Zn 66 0.017 Ge Zn 68 0.020 Ge As 75 0.025 Ge Se 77 0.093 Ge Se 82 0.064 Ge Ag 107 0.003 In Ag 109 0.002 In Cd 111 0.006 In Cd 114 0.003 In Sb 121 0.07 In Sb 123 0.07 In Tl 203 0.03 Th Tl 205 0.03 Th Pb 208 0.005 Th U 235 0.032 Th U 238 0.001 Th Mo 98 0.003† In Ba 135 0.008† In Sr 88 0.001‡ In
* IDLs were determined on a Perkin Elmer Elan 6000 ICP–MS using seven replicate analyses of a 1% nitric acid solution, at Manchester Environmental Laboratory, July 1996. † From EPA Method 200.8 for the Analysis of Drinking Waters—Application Note, Order No. ENVA-300A, The Perkin Elmer Corporation, 1996. ‡ From Perkin Elmer Technical Summary TSMS-12. TABLE 3125:IV.A. ELEMENTAL ABUNDANCE E QUATIONS AND C OMMON M OLECULAR I ON C ORRECTION E QUATIONS Elemental and Molecular Equations*†

Li 6  C 6 Be 9  C 9 Al 27  C 27 Sc 45  C 45 V 51  C 51 – (3.127)[( C 53) – (0.113  C 52)] Cr 52  C 52 Cr 53  C 53 Mn 55  C 55 Co 59  C 59 Ni 60  C 60 Ni 62  C 62 Cu 63  C 63 Cu 65  C 65 Zn 66  C 66 Zn 68  C 69 As 75  C 75 – (3.127)[( C 77) – (0.815  C 82)] Se 77  C 77 Se 82  C 82 – (1.008696  C 83) Sr 88  C 88 Mo 98  C 98 – (0.110588  C 101) Rh 103  C 103 Ag 107  C 107 Ag 109  C 109 Cd 111  C 111 – (1.073)[( C 108) – (0.712  C 106)] Cd 114  C 114 – (0.02686  C 119) Sb 121  C 121 Sb 123  C 123 – (0.127189  C 125) Ba 135  C 135 Ho 165  C 165 Tl 203  C 203 Tl 205  C 205 Pb 208  C 208  (1  C 206)  (1  C 207) Th 232  C 232 U 238  C 238

* C  calibration blank-corrected counts at indicated masses. † From EPA Method 200.8 for the Analysis of Drinking Water—Application Note, Order No. ENVA-300A, The Perkin Elmer Corporation, 1996. INDUCTIVELY COUPLED PLASMA–MASS SPECTROMETRY (3125)/ICP–MS Method

3TABLE 3125:IV.B. ELEMENTS , M ASSES , ABUNDANCES , AND C ORRECTION E QUATIONS (UPDATED 2008)

Isotope Mass Abundance Interference Calculation (if required)* Comments
Li (IS)† 6 7.52 C 6 - 0.08131  Li 7 Corrects for natural lithium in samples (I)‡ Be 9 100 C 9 C 13 1.108 C 13 For ArC 52 correction Al 27 100 C 27 Ca 43 0.13 C 43 - 0.0004  Sr 88 Corrects for Sr2  § Sc (IS) 45 100 C 45 V 51 99.76 C 51 - 3.1270  ClO 53 Corrects for variable chloride matrix (I) [not normally required in CCT Mode] Cr 52 83.76 C 52 - 0.0900  C 13 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  Ba 135 Ba2  interferes with Zn 68 Ge (IS) 72 27.43 C 72 Possibility of FeO (P) interference in high iron matrix As 75 100 C 75 - 3.1270  ArCl 77 Corrects for variable chloride matrix (I) Correction not required in CCT Mode (I) ArCl (Se 77) 77 C 77 - 0.8484  Se 82 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  Kr 83 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 Mo 98 ) Mo 98 24 C 98 - 0.1307  Ru 101 Corrects for variable ruthenium content (I) Ru 101 16.98 C 101 For Mo 98 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  Mo 95 Corrects for MoO (P) [not normally required in CCT Mode] Cd 114 28.81 C 114 - [0.0271  Sn 118 ] - [0.0028  Mo 95 ] Correction for MoO (P) and Sn (I) [MoO correction not normally required in CCT Mode] In (IS) 115 95.84 C 115 - 0.0142  Sn 118 Corrects for variable tin content (I) Sn 118 24.01 C 118 For Cd 114 and In 115 correction Sb 121 57.25 C 121 Sb 123 42.75 C 123 - 0.0449  Te 125 Corrects for variable tellurium content (I) Te 125 6.99 C 125 For Sb 123 correction Ba 135 6.59 C 135 Tb (IS) 159 100 C 159 Ho (IS) 165 100 C 165 Ho 2  may interfere with Se 82 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  Pb 206  1  Pb 207 Correction for variable lead abundance (I)

Bi (IS) 209 100 C 209 U 235 0.715 C 235 U 238 99.28 C 238

* All corrections should be verified and corrected for mass bias. † IS denotes an internal standard element. ‡ I denotes an isobaric correction. § Doubly charged corrections may vary with plasma tuning conditions and should be verified by the user before use.  P denotes correction that may vary with plasma tuning conditions and should be verified by the user before use. INDUCTIVELY COUPLED PLASMA–MASS SPECTROMETRY (3125)/ICP–MS Method

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### effect, which usually reduces the analyte signal, also is known as suppression . Correct for suppression by using internal standardization techniques.

2. Apparatus



### a. Inductively coupled plasma–mass spectrometer: Available from several manufacturers, this instrument includes a mass spectrometer, detector, an ICP source, mass flow controllers for regulating ICP gas flows, a peristaltic pump for introducing samples, and a computerized data acquisition and instrument control system. An x-y autosampler also may be used with appropriate control software.

b. Laboratory ware: Use pre-cleaned plastic laboratory ware for standard and sample preparation. Teflon * 

### —either tetrafluoroethylene hexafluoropropylene-copolymer (FEP), polytetrafluoroethylene (PTFE), or perfluoroalkoxy PTFE (PFA)—is preferred for standard preparation and sample digestion, while highdensity polyethylene (HDPE) and other dense, metal-freeplastics may be acceptable for internal standards, known-addition solutions, etc. Check each new lot of autosampler tubes for suitability, and pre-clean autosampler tubes and pipet tips if certificate of analysis is unavailable (see Section 3010C.2).

c. Air-displacement pipets, sized 10 to 100  L, 100 to 1000


L, and 1 to 10 mL. d. Analytical balance, accurate to 0.1 mg. e. Sample-preparation apparatus, such as hot plates, microwave digesters, and heated sand baths. Any sample-preparation device could introduce trace levels of target analytes to the sample.

f. Clean hood (optional), Class 100 (certified to contain less than 100 particles/m 3 

### ), for sample preparation and manipulation.If possible, perform all sample manipulations, digestions, dilutions, etc. in a certified Class 100 environment. Alternatively, handle samples in glove boxes, plastic fume hoods, or otherenvironments that minimize random contamination by trace metals.

3. Reagents



### a. Acids: Use ultra-high-purity grade (or equivalent) acids to prepare standards and process samples. Redistilled acids are acceptable if each batch is demonstrated to be uncontaminated by target analytes. Use extreme care when handling acids in the laboratory to avoid contaminating them with trace levels of metals.

1) Nitric acid (HNO 3 

### ) conc (specific gravity 1.41). 2) Nitric acid, 1  1: Add 500 mL conc HNO 3 

### to 500 mL reagent water.

3) Nitric acid, (v/v) 2%: Add 20 mL conc HNO 3 

### to 100 mL reagent water; dilute to 1000 mL.

4) Nitric acid, (v/v) 1%: Add 10 mL conc HNO 3 

### to 100 mL reagent water; dilute to 1000 mL.

b. Reagent water: When preparing blanks, standards, andsamples, use metal-free water that was prepared using the methods listed in Section 1080, described below, or provided elsewhere (if they have been proven effective). Use only high-purity

* Or equivalent. TABLE 3125:V. C OMMON M OLECULAR I ON INTERFERENCES IN ICP–MS 1

Molecular Ion Mass Element Measurement Affected by Interference
Background molecular ions:

NH  15 — OH  17 — OH 2  18 — C 2  24 Mg CN  26 Mg CO  28 Si N 2  28 Si N 2H  29 Si NO  30 — NOH  31 P O 2  32 S O 2H  33 — 36ArH  37 Cl 38 ArH  39 K 40ArH  41 — CO 2  44 Ca CO 2  H 45 Sc ArC  , ArO  52 Cr ArN  54 Cr ArNH  55 Mn ArO  56 Fe ArH  57 Fe 40Ar 36Ar  76 Se 40Ar 38 Ar 78 Se 40Ar2  80 Se Matrix molecular ions:

Bromide:

81 BrH  82 Se 79 BrO  95 Mo 81 BrO  97 Mo 81 BrOH  98 Mo Ar 81 Br  121 Sb Chloride:

35 ClO  51 V 35 ClOH  52 Cr 37 ClO  53 Cr 37 ClOH  54 Cr Ar 35 Cl  75 As Ar 37 Cl  77 Se Sulfate:

32 SO  48 Ti 32 SOH  49 — 34 SO  50 V, Cr 34 SOH  51 V SO 2  , S 2  64 Zn Ar 32 S  72 Ge Ar 34 S  74 Ge Phosphate:

PO  47 Ti POH  48 Ti PO 2  63 Cu ArP  71 Ga Group I & II metals:

ArNa  63 Cu ArK  79 Br ArCa  80 Se Matrix Oxides*

TiO 62-66 Ni, Cu, Zn ZrO 106-112 Ag, Cd MoO 108-116 Cd NbO 109 Ag
* Oxide interferences normally will be tiny and will affect method elements only when oxide-producing elements are present at relatively high concentrations, or when the instrument is improperly tuned or maintained. Preferably monitor Ti and Zr isotopes in soil, sediment, or solid waste samples, because these samples could contain high levels of such interfering elements. INDUCTIVELY COUPLED PLASMA–MASS SPECTROMETRY (3125)/ICP–MS Method

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### water to prepare samples and standards. Reagent water containing trace amounts of analyte elements will skew results.

Analysts can produce suitable reagent water using a multistage system that includes a softener/reverse osmosis unit, adual-column, strong acid/strong base ion exchange unit; an activated carbon filter; and a UV sterilization process. This will produce a polished water free of metals and organics.

c. Stock, standard, and other required solutions: See Sections 3111B, 3111D, 3114B, and 3120B.3 d on preparing standard stock solutions from elemental materials (pure metals, salts). Preferably, purchase high-purity, commercially prepared stocksolutions and dilute to required concentrations. Single- or multielement stock solutions (1000 mg/L) of the following elements are required: aluminum, antimony, arsenic, barium, beryllium,cadmium, cerium, chromium, cobalt, copper, germanium, indium, lead, magnesium, manganese, molybdenum, nickel, rhodium, scandium, selenium, silver, strontium, terbium, thallium, thorium, uranium, vanadium, and zinc. Prepare internal-standard and target-element stock solutions separately; they could be incompatible and cause precipitation or other solution instability.

1) Internal standard stock solution: Germanium, indium, lithium, scandium, and thorium are suggested as internal standards. The following masses are monitored: 72 

### Ge, 115 

### In, 6

### Li, 45 

### Sc, and
232

### Th. Add enough internal standard to all samples, standards, and quality control (QC) samples to give a suitable counts/ second (cps) signal and stability (100 000 to 300 000 cps for most internal standards). Minimize dilution-related errors by using an appropriately high concentration of internal standard mix solution. Maintain volume ratio for all internal standard additions.

Prepare internal standard mix as follows: Prepare a nominal 50-mg/L solution of 6

### Li by dissolving 0.15 g 6

### Li 2 

### CO 3 

### (isotopi

cally pure, i.e., 95% or greater purity†) in a minimal amount of 1:1 HNO 3 

### . Pipet 5.0 mL 1000-mg/L germanium, indium, scan

dium, and thorium standards into the lithium solution, diluteresulting solution to 500.0 mL, and mix thoroughly. The resultant concentration of Ge, In, Sc, and Th will be 10 mg/L. Determine the internal standard concentrations required to achieve acceptable levels of precision, and dilute the internal standard stock accordingly.

Other internal standards, such as bismuth, holmium, rhodium, terbium, and yttrium, may also be used in this method. Ensure that the internal standard mix used is stable and that there are no undesired interactions among elements.

All new sample matrices should be screened for internalstandard elements before analysis. Analyzing a few representative samples for internal standards should be sufficient. Analyze samples “as received” or “as digested” (before adding internalstandard), then add internal standard mix and re-analyze. Monitor counts at the internal standard masses. If the “as received” or “as digested” samples show appreciable detector counts (10% or higher of samples with added internal standard), dilute sample oruse another internal standard. If the response of a sample containing the internal standard is not within 70% to 125% of the response for a calibration blank with the internal standard, eitherdilute the sample before analysis or use another internal standard. During actual analysis, monitor internal standard masses and note all internal standard recoveries that are more than 125%of the internal standard response in the calibration blank. Interpret results for these samples with caution.

The internal standard mix may be added to blanks, standards, and samples via a “Y” connector after the peristaltic pump to mix it with the sample stream during sample introduction.

2) Instrument optimization/tuning solution, containing beryllium, cadmium, cobalt, copper, germanium, indium, rhodium,scandium, terbium, thallium, (for sensitivity and stability evaluation), barium (for doubly-charged evaluation), cerium (for oxide evaluation), magnesium (mass calibration check), and lead (mass calibration check). Prepare this solution in 2% HNO 3 

### . This mix includes all common elements used to optimize and tune various ICP–MS operating parameters. It may be possible to use fewer elements in this solution, depending on the instrument manufacturer’s recommendations.

3) Calibration standards: A five standard calibration is recommended, from 0 to 100  g/L.‡ Other calibration regimes are acceptable if the full suite of quality assurance samples and standards is run to validate any method changes. Fewer standardsmay be used, and a two-point blank/mid-range calibration technique commonly used in ICP optical methods should also produce acceptable results. Calibrate all analytes using the selected concentrations. Prepare all calibration standards and blanks in a matrix of 2% nitric acid. Add internal standard mix to allcalibration standards to provide appropriate count rates for interference correction. N OTE 

### : Add the same ratio of internal standard mix to all standards and blanks used in this method.

4) Method blank (MB): A method blank (also known as reagent blank) is a portion of reagent water (¶ 3 b ) treated exactly as a sample, including exposure to all equipment, glassware, procedures, and reagents. It is used to assess whether analytes or interferences are present in the analytical process or system. No MB should contain a warning level of any analyte of interest (based on the end user’s requirements). Undertake immediate corrective action for MB measurements above the minimum reporting level (see Section 3020). Include at least one MB with each batch of samples prepared. For dissolved samples, take reagent water through same filtration and preservation processesused for samples. For samples requiring digestion, process reagent water with the same digestion techniques as samples. Add internal standard mix to method blank.

5) Calibration verification standard: Prepare a mid-rangestandard using a different source than that used for the calibration standards, in 2% HNO 3 

### , with equivalent addition of internal standard.

6) Calibration verification blank: Use 2% HNO 3 

### , the same solution as the zero calibration standard.

7) Laboratory-fortified blank (LFB): The laboratory-fortified blank (also known as a blank spike ) is a method blank that has been fortified with a known concentration of analyte. It is usedto evaluate ongoing laboratory performance and analyte recovery in a clean matrix. Prepare fortified concentrations approximating the midpoint of the calibration curve (50 ng/mL) or lower with stock solutions prepared from a different source than that used to develop working standards. Calculate percent recovery, plot control charts, and determine control limits for these meas-

† Cambridge Isotope Laboratories or equivalent. ‡ Performance data for the method were obtained with these concentrations. INDUCTIVELY COUPLED PLASMA–MASS SPECTROMETRY (3125)/ICP–MS Method

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### urements. Ensure that the LFB meets the method’s performance criteria when such criteria are specified. Establish corrective actions to be taken in case the LFB does not satisfy acceptance criteria. Include at least one LFB with each batch of samples prepared. This standard, sometimes also called a laboratory control sample (LCS), is used to validate digestion techniques and known-addition levels.

8) Reference materials: Use externally prepared reference material, preferably from National Institute of Standards and Technology§ (NIST) 1643 series or equivalent.

9) Known-addition solution for samples: Add stock standard to sample so the volume change is less than 5%. In the absence of information on analyte levels in the sample, prepare known additions at around 50  g/L or lower. If analyte concentration levels are known, add at 50% to 200% of the sample levels. For samples undergoing digestion, make additions before digestion.For dissolved metals determinations, make additions after filtration, preferably immediately before analysis.

10) Low-level standards: Use both a 0.3- and a 1.0-  g/L standard when expected analyte concentration is less than 5


g/L. Prepare both standards in 2% nitric acid. Prepare volumetrically a mixed standard containing the method analytes at desired concentration(s) (0.30  g/L, 1.0


g/L, or both). Prepare weekly in 100-mL quantities. d. Argon: Use a prepurified grade of argon unless it can bedemonstrated that other grades can be used successfully. Prepurified argon is usually necessary because technical argon oftencontains significant levels of impurities (e.g., carbon and krypton). 82 

### Kr interferes with the determination of 82 

### Se. Monitor 83 

### Kr at all times.

4. Procedures



### a. Sample preparation: See Sections 3010 and 3020 for general guidance and additional specific requirements on sampling and quality control. See Section 3030E for the recommended sample-digestion technique for all analytes except silver and antimony. Use the method in Section 3030F for silver and antimony, paying special attention to chloride ion interferencesand using all applicable elemental corrections. Alternative digestion techniques and more guidance on sample preparation are available. 3,4



### Ideally, use a “clean” environment when handling, manipulating, or preparing samples. Preferably perform all sample manipulations in a Class 100 clean hood or room to minimize potential contamination artifacts in digested or filtered samples.

b. Instrument operating conditions: Follow manufacturer’s standard operating procedures for initialization, mass calibration,gas flow optimization, and other instrument operating conditions. Maintain complete, detailed information on the instrument’s operating status whenever it is used.

c. Analytical run sequence: Table 3125:VI outlines a suggested analytical run sequence, including tuning and optimizingthe instrument, checking reagent blanks, calibrating the instrument, verifying the calibration, analyzing samples, and analyzing quality control samples and blanks. d. Instrument tuning and optimization: Follow manufacturer’s instructions for optimizing instrument performance. The mostimportant optimization criteria include nebulizer gas flows, detector and lens voltages, radio-frequency forward power, andmass calibration. Periodically check mass calibration and instrument resolution. Ideally, optimize the instrument to minimize the formation of oxide and doubly charged species. Measure CeO  

### : Ce  

### and Ba2  

### :Ba  

### ratios to monitor the formation of oxide and doubly charged species, respectively. Both ratios should meetthe manufacturer’s criteria before instrument calibration. Monitor background counts at mass 220 after optimization, and compare with manufacturer’s criteria. (See Table 3125:VII for a summary of method performance criteria related to optimization and tuning, calibration, and analytical performance.)

e. Instrument calibration: After optimization and tuning, cal- ibrate the ICP–MS using an appropriate range of calibration § National Institute of Standards and Technology, www.nist.gov TABLE 3125:VI. S UGGESTED ANALYTICAL RUN S EQUENCE Sample Type Comments
Tuning/optimization standard Check mass calibration and resolution Tuning/optimization standard Optimize instrument for maximum rhodium counts while keeping oxides, double-charged ions, and background within instrument specifications Rinse — Reagent blank Check for contamination Reagent blank Calibration standard blank 5-  g/L standard — 10-  g/L standard — 20-  g/L standard — 50-  g/L standard — 100-  g/L standard — Rinse Check for memory Initial calibration

verification, 50  g/L Check for calibration
accuracy Initial calibration blank Check for memory 0.30-  g/L standard Low-level calibration verification 1.0-  g/L standard Low-level calibration verification External reference material NIST 1643c or equivalent Continuing calibration

verification Check for calibration stability

Continuing blank calibration Check for memory Project sample method blank Check for contaminationProject sample laboratoryfortified blank Check for spike recovery

Project sample 1-4 Check for possible interferences Project sample 5 — Project sample 5 with known

addition Check for spike recovery

Project sample 5 duplicate

with known addition Check for reproducibility

Continuing calibration

verification (every 10 samples) Check for calibration stability

Continuing calibration blank

(every 10 samples) Check for memory INDUCTIVELY COUPLED PLASMA–MASS SPECTROMETRY (3125)/ICP–MS Method

7

### standards. Use appropriate regression techniques to determinecalibration responses for each analyte. For acceptable calibrations, the regression curves’ correlation coefficients are ideally 0.995 or greater.

Immediately after calibration, run initial calibration verification standard, ¶ 3 c 5); acceptance criteria are 10% of known analyte concentration. Next, run initial calibration verification blank, ¶ 3 c 6); acceptance criteria are ideally the absolute value of the instrument detection limit for each analyte, but in practice,
the absolute value of the laboratory reporting limit or the laboratory method detection limit for each analyte is acceptable. If analyte concentrations are less than 5  g/L, verify low-level calibration by using a standard at 40% to 50% of the highest low-level standard.

f. Sample analysis: Ensure that all vessels and reagents areuncontaminated. During the analytical run, include quality-control analyses according to schedule of Table 3125:VIII or follow project-specific QA/QC protocols.

Internal standard recoveries must be between 70% and 125% of internal standard response in the laboratory-fortified blank;otherwise, dilute sample, add internal standard mix, and reanalyze.

Make known-addition analyses for each matrix in a digestion or filtration batch.

5. Calculations and Corrections



### Configure instrument software to report internal-standardcorrected results. Water sample results should be reported in micrograms per liter. Report appropriate number of significant figures.

a. Correction for dilutions and solids: Correct all dilution results, and raise the related reporting limits accordingly:

R Corr R Uncorr  V  V

s / V



### where: R Corr  diluted corrected results,  g/L, R Uncorr  uncorrected elemental results,  g/L, V  volume of digestate (after digestion), L, and V

s  volume of undiluted sample, L. 

### Use Method 2540B to determine total solids in solid samples, and report results as micrograms per kilogram, dry weight. Correct all results for solids content of solid samples. Use the following equation to correct solid or sediment sample results for dilution during digestion and moisture content:

R corr R uncorr  V
W  % TS/100



### where: R
corr  corrected result,  g/kg, R
uncorr  uncorrected elemental result,  g/L, V  volume of digestate (after digestion), L, W  mass of the wet sample, kg, and % TS  percent total solids determined in the sample. TABLE 3125:VII. S UMMARY OF PERFORMANCE C RITERIA

Performance Characteristic Criteria
Mass resolution Manufacturer’s specification Mass calibration Manufacturer’s specification Ba2  /Ba  Manufacturer’s specification CeO/Ce Manufacturer’s specification Background counts at

mass 220 Manufacturer’s specification

Correlation coefficient  0.995 Calibration blanks  Reporting limit Calibration verification

standards 10% of true value

Laboratory fortified blank

(control sample) 30% of true value

Precision 20% relative percent difference for lab duplicates Known-addition recovery 75-125% 0.3 and 1.0  g/L standards Dependent on data quality objectives Reference materials Dependent on data quality objectives Internal standard response 70-125% of response in calibration blank with known addition

TABLE 3125:VIII. Q UALITY C ONTROL ANALYSES FOR ICP–MS M ETHOD Analysis Frequency Acceptance Criteria

Reference material [¶ 3 c 9] Greater of: once per sample batch, or 5% Dependent on data quality objectives Preparatory/method blank [¶ 3 c4)] 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 [¶ 3 c7)] 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 [¶ 3 c 5)] 10% 10% of known concentration

Continuing calibration verification

blank [¶ 3 c 6)] 10% Absolute value of instrument detection limit; absolute value of laboratory reporting limit or MDL is acceptable INDUCTIVELY COUPLED PLASMA–MASS SPECTROMETRY (3125)/ICP–MS Method

8

### b. Compensation for interferences : Use instrument software to correct for previously listed interferences. See Table 3125:V for a list of the most common molecular ion interferences.

c. Data reporting: Establish appropriate reporting limits for method analytes based on IDLs and the laboratory blank. For regulatory programs, ensure that reporting limits for method analytes are a factor of three below relevant regulatory criteria whenever possible.

If method blank contamination is typically random, sporadic, or otherwise not statistically controllable, do not correct results for the method blank. Consider correcting blank results only if it can be demonstrated that the blank’s analyte concentration is within statistical control over a period of months. Report allmethod blank data explicitly in a manner identical to samplereporting procedures.

d. Documentation: Maintain documentation for the following(where applicable): instrument tuning, mass calibration, calibration verification, analyses of blanks (method, field, calibration, and equipment blanks), IDL and MDL studies, analyses of samples and duplicates with known additions, laboratory and field duplicate information, serial dilutions, internal standard recoveries, and any relevant quality control charts.

Also, maintain all raw data generated in support of the method, and keep them available for review. 5 

### 6. Method Performance



### Table 3125:III presents IDL data generated by this method; this represents optimal instrument detection capabilities, not recommended method detection or reporting limits. Tables3125:I, II, and IX through XI contain single-laboratory, singleoperator, single-instrument performance data generated by thismethod for calibration verification standards, low-level standards, and known-addition recoveries for freshwater matrices, as well as data showing standard and CCT performance data for elements usually affected by polyatomic interferences (Tables 3125:I and II). Section 3125 performance data for some analytes are currently unavailable; however, performance data for similar ICP-MS methods are available in the literature. 1,4



### 7. References

1. U.S. ENVIRONMENTAL PROTECTION A GENCY . 1994. Determination of

trace elements in waters and wastes by inductively coupled plasmamass spectrometry, Method 200.8. U.S. Environmental Protection Agency, Environmental Monitoring Systems Lab., Cincinnati, Ohio. 2. U.S. ENVIRONMENTAL PROTECTION A GENCY . 1984. Definition and procedure for the determination of the method detection limit, revision 1.11. 40 CFR 136, Appendix B. TABLE 3125:IX. M ETHOD PERFORMANCE WITH C ALIBRATION V ERIFICATION S TANDARDS *
Continuing Calibration Verification Standard (N  44) Initial Calibration Verification Standard (N  12)

Element Mass Mean Recovery % Mean


g/L Standard Deviation



g/L Relative Standard Deviation % Mean Recovery % Mean


g/L Standard Deviation



g/L Relative Standard Deviation %

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 Ag 107 101.50 50.75 1.68 3.30 99.27 49.63 1.17 2.36 Ag 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
* Single-laboratory, single-operator, single-instrument data, determined using a 50-  g/L standard prepared from sources independent of calibration standard source. Data acquired January–November 1996 during actual sample determinations. Performance of continuing calibration verification standards at different l evels may vary. Perkin-Elmer Elan 6000 ICP–MS used for determination. INDUCTIVELY COUPLED PLASMA–MASS SPECTROMETRY (3125)/ICP–MS Method

9TABLE 3125:X. M ETHOD PERFORMANCE FOR RECOVERY OF KNOWN ADDITION IN NATURAL WATERS *
Total Recoverable Metals† Dissolved Metals‡

Element Mass Mean Recovery % Relative Standard Deviation % Mean Recovery % Relative Standard Deviation %

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 Ag 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
* 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. † Known-addition level 20  g/L. Additions made before preparation according to Section 3030E (modified by clean-hood digestion in TFE beakers). N  20. ‡ Known-addition level for Cd and Pb 1  g/L; for other analytes 10  g/L. Additions made after filtration through 1:1 HNO 3 precleaned 0.45-  m filters. N  28.

TABLE 3125:XI. M ETHOD PERFORMANCE WITH C ALIBRATION V ERIFICATION S TANDARDS *

1.0-  g/L Standard 0.3-  g/L Standard

Element Mass Mean Recovery % Mean


g/L Standard Deviation


g/L Relative Standard Deviation % Mean Recovery % Mean


g/L Standard Deviation


g/L Relative Standard Deviation %

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
* Single-laboratory, single-operator, single-instrument data. N  24 for both standards. INDUCTIVELY COUPLED PLASMA–MASS SPECTROMETRY (3125)/ICP–MS Method

103. U.S. ENVIRONMENTAL PROTECTION A GENCY . 1991. Methods for thedetermination of metals in environmental samples. U.S. Environmental Protection Agency, Off. Research & Development, Washington D.C. 4. U.S. ENVIRONMENTAL PROTECTION A GENCY . 1995. Method 1638: Determination of trace elements in ambient waters by inductively coupled plasma mass spectrometry. U.S. Environmental Protection Agency, Off. Water, Washington, D.C. 5. U.S. ENVIRONMENTAL PROTECTION A GENCY . 1995. Guidance on the Documentation and Evaluation of Trace Metals Data Collected forClean Water Act Compliance Monitoring. U.S. Environmental Protection Agency, Off. Water, Washington, D.C.



### 8. Bibliography

GRAY , A.L. 1974. A plasma source for mass analysis . Proc. Soc. Anal. Chem . 11:182. H AYHURST , A.N. & N.R. TELFORD . 1977. Mass spectrometric sampling ofions from atmospheric pressure flames. I. Characteristics and calibration of the sampling system. Combust. Flame . 67. H OUK , R.S., V.A. FASSEL , G.D. FLESCH , H.J. S VEC , A.L. GRAY & C.E. TAYLOR . 1980. Inductively coupled argon plasma as an ion source for mass spectrometric determination of trace elements. Anal. Chem . 52:2283. D OUGLAS , D.J. & J.B. FRENCH . 1981. Elemental analysis with a microwave-induced plasma/quadrupole mass spectrometer system. Anal. Chem . 53:37. H OUK , R.S., V.A. FASSEL & H.J. S VEC . 1981. Inductively coupled plasma–mass spectrometry: Sample introduction, ionization, ion extraction, and analytical results. Dyn. Mass Spectrom . 6:234. O LIVARES , J.A. & R.S. H OUK . 1985. Ion sampling for inductively coupled plasma–mass spectrometry. Anal. Chem . 57:2674. H OUK , R.S. 1986. Mass spectrometry of inductively coupled plasmas. Anal. Chem . 58:97. T HOMPSON , J.J. & R.S. H OUK . 1986. Inductively coupled plasma–mass spectrometric detection for multi-element flow injection analysis and elemental speciation by reversed-phase liquid chromatography. Anal. Chem . 58:2541. V AUGHAN , M.A. & G. H ORLICK . 1986. Oxide, hydroxide, and doublycharged analyte species in inductively coupled plasma/mass spectrometry. Appl. Spectrosc. 40:434. B EAUCHEMIN , D., J.W. MCLAREN , A.P. MYKYTIUK & S.S. B ERMAN . 1987. Determination of trace metals in a river water reference material by inductively coupled plasma mass spectrometry. Anal. Chem . 59:778. GARBARINO , J.R. & H.E. TAYLOR . 1987. Stable isotope dilution analysisof hydrologic samples by inductively coupled plasma–mass spectrometry. Anal. Chem . 59:1568. T HOMPSON , J.J. & R.S. H OUK . 1987. A study of internal standardization in inductively coupled plasma–mass spectrometry. Appl. Spectrosc. 41:801. JARVIS , K.E., A.L. GRAY & R.S. H OUK . 1992. Inductively Coupled Plasma–Mass Spectrometry. Blackie Academic & Professional, Chapman & Hall, New York, N.Y. TAYLOR , D.B., H.M. KINGSTON , D.J. N OGAY , D. KOLLER & R. HUTTON

. 1996. On-line solid-phase chelation for the determination of eightmetals in environmental waters by Inductively Coupled Mass Spectrometry. J. Anal. Atom. Spectrom. 11:187. KINGSTON , H.M.S. & S. H ASWELL , eds. 1997. Microwave Enhanced Chemistry: Fundamentals, Sample Preparation, and Applications. ACS Professional Reference Book Ser., American Chemical Soc., Washington, D.C. U.S. ENVIRONMENTAL PROTECTION A GENCY . 1998. Inductively coupled plasma–mass spectrometry, Method 6020. In Solid Waste Methods,SW846, Update 4. U.S. Environmental Protection Agency, Environmental Monitoring Systems Lab., Cincinnati, Ohio. NELMS , S., ed. 2005. Inductively Coupled Plasma Mass Spectrometry Handbook. Blackwell Science, Cambridge, Mass. B ECKER J.S. 2008. Inorganic Mass Spectrometry: Principles and Applications. Wiley InterScience, Malden, Mass. INDUCTIVELY COUPLED PLASMA–MASS SPECTROMETRY (3125)/ICP–MS Method

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