**SW-846 Update V 6020B - 1 Revision 2**  **July 2014 METHOD 6020B** 

**INDUCTIVELY COUPLED PLASMA—MASS SPECTROMETRY**

**SW-846 is not intended to be an analytical training manual. Therefore, method**  **procedures are written based on the assumption that they will be performed by analysts who are**  **formally trained in at least the basic principles o f chemical analysis and in the use of the subject**  **technology.**

**In addition, SW-846 methods, with the exception of required method use for the analysis**  **of method-defined parameters, are intended to be gu idance methods which contain general**  **information on how to perform an analytical procedu re or technique which a laboratory can use**  **as a basic starting point for generating its own de tailed standard operating procedure (SOP),**  **either for its own general use or for a specific pr oject application. The performance data**  **included in this method are for guidance purposes o nly, and are not intended to be and must not**  **be used as absolute quality control (QC) acceptance criteria for purposes of laboratory** 

**accreditation.**

**1.0 SCOPE AND APPLICATION**

**1.1 Inductively coupled plasma-mass spectrometry ( ICP-MS) is applicable to the**  **determination of sub-μg/L concentrations of a large number of elements in water samples and in**  **waste extracts or digests (Refs. 1 and 2). When di ssolved constituents are required, samples**  **must be filtered and acid-preserved prior to analys is. No digestion is required prior to analysis**  **for dissolved elements in water samples. Acid dige stion prior to filtration and analysis is**  **required for groundwater, aqueous samples, industri al wastes, soils, sludges, sediments, and**  **other solid wastes for which total (acid-leachable) elements are required. The analyst should**  **insure that a sample digestion method is chosen tha t is appropriate for each analyte and the**  **intended use of the data. Refer to Chapter Three fo r the appropriate digestion procedures.** 

**1.2 ICP-MS has been applied to the determination o f over 60 elements in various**  **matrices. Analytes for which the acceptability of Method 6020 has been demonstrated through**  **multi-laboratory testing on solid and aqueous waste s are listed below.** 

**Element Symbol**  **CASRN a**  **Element Symbol**  **CASRN a** 

**Aluminum Al**  **7429-90-5 Magnesium**  **Mg 7439-95-4** 

**Antimony Sb**  **7440-36-0 Manganese**  **Mn 7439-96-5** 

**Arsenic As**  **7440-38-2 Mercury**  **Hg 7439-97-6** 

**Barium Ba**  **7440-39-3 Nickel**  **Ni 7440-02-0** 

**Beryllium Be**  **7440-41-7 Potassium**  **K 7440-09-7** **SW-846 Update V 6020B - 2 Revision 2**  **July 2014 Element**  **Symbol CASRN**  **a Element**  **Symbol CASRN**  **a**

**Cadmium Cd**  **7440-43-9 Selenium**  **Se 7782-49-2** 

**Calcium Ca**  **7440-70-2 Silver**  **Ag 7440-22-4** 

**Chromium Cr**  **7440-47-3 Sodium**  **Na 7440-23-5** 

**Cobalt Co**  **7440-48-4 Thallium**  **TI 7440-28-0** 

**Copper Cu**  **7440-50-8 Vanadium**  **V 7440-62-2** 

**Iron Fe**  **7439-89-6 Zinc**  **Zn 7440-66-6** 

**Lead Pb**  **7439-92-1**

**a Chemical Abstract Service Registry Number** 

**The performance acceptability of ICP-MS for the de termination of the listed elements was**  **based upon comparison of the multi-laboratory testi ng results with those obtained from either**  **furnace atomic absorption spectrophotometry or indu ctively coupled plasma—optical emission**  **spectrometry. It should be noted that one multi-la boratory study was conducted in 1988. As** 

**advances in ICP-MS instrumentation and software hav e been made since that time, other**  **elements have been added through validation and wit h additional improvements in performance**  **of the method. Performance, in general, presently exceeds the original multi-laboratory**  **performance data for the listed elements (and other s) that are provided in Sec. 13.0. Instrument**  **detection limits (IDLs), lower limits of quantitati on (LLOQs) and linear ranges will vary with the**  **matrices, instrumentation, and operating conditions . In relatively simple matrices, IDLs will**  **generally be < 0.1 μg/L. For less sensitive elemen ts (e.g., Se and As) and desensitized major**  **elements, IDLs may be** ≥ **1.0 μg/L.**

**1.3 If Method 6020 is used to determine any analyt e not listed in Sec. 1.2, it is the**  **responsibility of the analyst to demonstrate the pr ecision and bias of the method for the waste to**  **be analyzed. The analyst must always monitor poten tial sources of interferences and take**  **appropriate action to ensure data of known quality (see Sec. 9.0). Other elements and matrices**  **may be analyzed by this method if performance is de monstrated**  **for the analyte of interest, in the matrices of interest, at the concentration leve**  **ls of interest in the same manner as the listed elements and matrices (see Sec. 9.0).** 

**1.4 Use of this method should be restricted to sp ectroscopists who are knowledgeable**  **in the recognition and correction of spectral, chem ical, and physical interferences in ICP-MS**  **analysis.**

**1.5 An appropriate internal standard is necessary for each analyte determined by** 

**ICP-MS. Recommended internal standards are 6**  **Li, 45**  **Sc, 89**  **Y, 103**  **Rh, 115**  **In, 159**  **Tb, 165**  **Ho, and**

**209 Bi. The lithium internal standard should have an en**  **riched abundance of 6**  **Li, so that SW-846 Update V 6020B - 3**  **Revision 2 July 2014**  **interference from lithium native to the sample is m inimized. Other elements may need to be**  **used as internal standards when samples contain sig nificant native amounts of the**  **recommended internal standards as indicated by high bias of internal standard recoveries.** 

**Note: Other potential causes of a high bias should also be considered before a final decision is**  **made that the internal standard high bias is caused by an excessive concentration of the**  **internal standard isotope in the sample.**

**1.6 Prior to employing this method, analysts are a dvised to consult the preparatory**  **method for each type of procedure that may be emplo yed in the overall analysis (e.g., Methods**  **3005, 3010, 3015, 3031, 3040, 3050, 3051, 3052, 700 0, and 6800) for additional information on**  **QC procedures, development of QC acceptance criteri a, calculations, and general guidance.**  **Analysts also should consult the disclaimer stateme nt at the front of the manual and the**  **information in Chapter Two for guidance on the inte nded flexibility in the choice of methods,**  **apparatus, materials, reagents, and supplies, and o n the responsibilities of the analyst for**  **demonstrating that the techniques employed are appr opriate for the analytes of interest, in the**  **matrix of interest, and at the levels of concern.**

**In addition, analysts and data users are advised th at, except where explicitly specified in a**  **regulation, the use of SW-846 methods is** not **mandatory in response to Federal testing requirements. The information contained in this me**  **thod is provided by EPA as guidance to be used by the analyst and the regulated community in**  **making judgments necessary to generate results that meet the data quality objectives (DQOs**  **) for the intended application.**

**1.7 This method is restricted to use by, or under supervision of, properly experienced**  **and trained personnel. Each analyst must demonstra te the ability to generate acceptable** 

**results with this method.**

**2.0 SUMMARY OF METHOD**

**2.1 Prior to analysis, aqueous and solid samples a re solubilized or digested using the**  **appropriate sample preparation methods (see Chapter Three). When analyzing groundwater**  **samples for dissolved constituents, acid digestion is not necessary, if the samples are filtered**  **and acid-preserved prior to analysis (e.g., Methods 3005, 3010, 3015, 3031, 3050, 3051 and**  **3052). For oils, greases, or waxes, use the solvent dissolution procedure in method 3040 to**  **prepare the samples.**

**2.2 This method describes multi-element determinat ions using ICP-MS in**  **environmental samples. The method measures ions pr oduced by a radio-frequency inductively**  **coupled plasma. Analyte species in liquid are nebu lized and the resulting aerosol is transported**  **by argon gas into the plasma torch. The ions produ ced by high temperatures are entrained in**  **the plasma gas and introduced, by means of an inter face, into a mass spectrometer. The ions**  **produced in the plasma are sorted according to thei r mass-to-charge (**  m/z **) ratios and quantified with a channel electron multiplier. Interferences**  **must be assessed and valid corrections applied or the data flagged to indicate problems. Interfer**  **ence correction must include compensation for background ions contributed by the plasma gas, reag**  **ents, and constituents of the sample**

**matrix. SW-846 Update V 6020B - 4**  **Revision 2 July 2014**  **3.0 DEFINITIONS**

**Refer to Chapter One, Chapter Three, and the manuf acturer's instructions for definitions**  **that may be relevant to this procedure.**

**4.0 INTERFERENCES**

**4.1 Isobaric elemental interferences in ICP-MS are caused by isotopes of different**  **elements forming atomic ions with the same nominal** m/z **ratio. A data system must be used to**

**correct for these interferences. This involves det ermining the signal for another isotope of the**  **interfering element and subtracting the appropriate signal from the analyte isotope signal.** 

**4.2 Isobaric molecular and doubly charged ion inte rferences in ICP-MS are caused by**  **ions consisting of more than one atom or charge, re spectively. Most isobaric interferences that** 

**could affect ICP-MS determinations have been identi fied in the literature (Refs. 3 and 4).**  **Examples include 75**  **ArCl +**  **ion on the 75**  **As signal and MoO +**  **ions on the cadmium isotopes. While the approach used to correct for molecular isobaric**  **interferences is demonstrated below using the natural isotope abundances from the literature**  **(Ref. 5), the most precise coefficients for an**

**instrument can be determined from the ratio of the net isotope signals**  observed **for a standard solution of the interfering element at a concentrat**  **ion which produces sufficient interference at the isotopes of interest that a reliable measuremen**  **t can be made. Because the 35**  **Cl natural**

**abundance of 75.77% is 3.13 times the 37**  **Cl abundance of 24.23%, the chloride correction for arsenic can be calculated (approximately) as follow**  **s (where the 38**  **Ar 37**  **Cl +**  **contribution at** m/z **75 is a negligible 0.06% of the**  **40 Ar**  **35 Cl**  **+ signal):** 

Corrected

**arsenic signal (using the abundances of natural is otopes**  **for coefficient approximations) =**

**(** m/z **75 signal) - (3.13) [(** m/z **77 signal) - (0.87) (** m/z **82 signal)]**

**where, the final term adjusts for any selenium con tribution at 77**  m/z

**,**

**NOTE : Arsenic values can be biased high by this type o**  **f equation when the net signal at** m/z **82 is caused by ions other than 82**  **Se +**  **, (e.g., 81**  **BrH +**  **from bromine wastes [Ref. 6]).**

**NOTE : The coefficients should be verified experimentall**  **y using the procedures or coefficients provided by the instrument manufacturer.** 

**Similarly,**

Corrected **cadmium signal (using the abundances of natural is otopes**  **for coefficient approximations) =**

**(** m/z **114 signal) - (0.027)(** m/z **118 signal) - (1.63)(** m/z **108 signal) SW-846 Update V 6020B - 5**  **Revision 2 July 2014**  **where, the last 2 terms adjust for any 114**  **Sn +**  **or 114**  **MoO +**  **contributions at** m/z **114.**

**NOTE : Cadmium values will be biased low by this type o**  **f equation when 92**  **ZrO +**  **ions contribute**

**at** m/z **108, but use of** m/z

**111 for Cd is even subject to direct ( 94**  **ZrOH +**  **) and indirect (**  **90 ZrO**  **+ ) additive interferences when Zr is present.** 

**NOTE : With respect to the arsenic equation above, the**  **coefficients could be improved. For example, the coefficient to modify “3.13” (in the e**  **quation above) for a particular**

**instrument can be determined from the observed rati o of the m/z 75 to the m/z 77 net**  **isotope signals for a solution of hydrochloric acid . The concentration of HCl used**  **should provide enough signal at the measured isotop es to ensure that a reliable**  **measurement can be made, while not exceeding the li near range of the detector.** 

**The accuracy of these types of equations is based upon the constancy of the**  observed **isotopic ratios for the interfering species. Corre ctions that presume a constant fraction of a**  **molecular ion relative to the "parent" ion have not been found (Ref. 7) to be reliable, e.g., oxide**  **levels can vary with operating conditions. If a co rrection for an oxide ion is based upon the ratio**  **of parent-to-oxide ion intensities, the correction must be adjusted for the degree of oxide**  **formation by the use of an appropriate oxide intern al standard previously demonstrated to form** 

**a similar level of oxide as the interferent. For example, this type of correction has been**  **reported (Ref. 7) for oxide-ion corrections using T hO**  **+ /Th**  **+ for the determination of rare earth** 

**elements. The use of aerosol desolvation and/or mi xed gas plasmas have been shown to**  **greatly reduce molecular interferences (Ref. 8). T hese techniques can be used, provided that**  **IDL, bias, and precision specifications for analysi s of the samples can be met.** 

**4.3 As technology continues to develop, modificatio ns to existing ICP-MS**  **instrumentation can reduce or completely remove com mon interferences thus eliminating the**  **need for reliance on correction equations. Instrume nts must be able to demonstrate successful**  **freedom from interferences. Examples of such modifi cations are discussed in more detail below:** 

**4.3.1 Recent ICP-MS instruments may include collisi on or reaction cells for** 

**removal of molecular isobaric interferences. This t ype of interference removal is effective,**  **and highly recommended for complex and/or varying m atrices. The systems work either by**  **collision of molecular species with an inert gas (u sually helium) or by reaction of molecular**  **species or the target analyte with reactive gases ( e.g., ammonia or methane).** 

**Manufacturer recommendations should be followed for the configuration of the**  **collision/reaction cell. This technique may elimina te the need for most correction**  **equations, but freedom from interference still need s to be demonstrated using the spectral**  **interference check (SIC) solutions described in sec tions 7.23 and 9.9.** 

**4.3.2 High resolution ICP-MS instruments are availa ble based on several mass**  **analyzer designs with much higher mass resolution w ithin the mass range of traditional**  **ICP-MS instruments. These mass analyzers are not b ased on quadrupole mass**  **analyzers and have orders of magnitude resolution a bove quadrupoles, which helps**  **reduce or eliminate interference from polyatomic io ns with the same nominal mass. These**  **mass analyzers reduce or eliminate the need for mos t correction equations, but the**  **instrument needs to be operated at sufficient resol ution to remove the expected** **SW-846 Update V 6020B - 6 Revision 2**  **July 2014 interference. For example, resolving**  **52 Cr from**  **40 Ar**  **12 C requires a resolution of around**  **4000, while resolving 75**  **As from 40**  **Ar 35**  **Cl requires a resolution of around 8000. Freedom**

**from interferences needs to be demonstrated for the particular higher resolution mass**  **analyzers ICP-MS.**

**4.4 Additionally, solid-phase chelation may be use d to eliminate isobaric interferences** 

**from both element and molecular sources. An on-lin e method has been demonstrated for**  **environmental waters such as sea water, drinking wa ter and acid decomposed samples. Acid**  **decomposed samples refer to samples decomposed by m ethods similar to methods 3052,**  **3051, 3050 or 3015. Samples with** % **levels of iron and aluminum should be avoided. Th e**  **method also provides a method for preconcentration to enhance detection limits simultaneously** 

**with elimination of isobaric interferences. The me thod relies on chelating resins such as**  **imminodiacetate or other appropriate resins and sel ectively concentrates the elements of**  **interest while eliminating interfering elements fro m the sample matrix. By eliminating the** 

**elements that are direct isobaric interferences or those that form isobaric interfering molecular**  **masses, the mass region is simplified and these int erferences cannot occur. The method has**  **been proven effective for the certification of refe rence materials and validated using reference**  **materials (Refs. 13-15). The method has the potent ial to be used on-line or off-line as an**  **effective sample preparation method specifically de signed to address interference problems.** 

**4.5 Since commercial quadrupole ICP-MS instruments nominally provide unit**  **resolution at 10% of the peak height, very high ion currents at adjacent masses can also**  **contribute to ion signals at the mass of interest. Although this type of interference is**  **uncommon, it is not easily corrected, and samples e xhibiting a significant problem of this type**  **could need resolution improvement, matrix separatio n, or analysis using another verified and**  **documented isotope, or otherwise the use of another method.** 

**4.6 Physical interferences are associated with the sample nebulization and transport**  **processes as well as with ion-transmission efficien cies. Nebulization and transport processes**  **can be affected if a matrix component causes a chan ge in surface tension or viscosity.**  **Changes in matrix composition can cause significant signal suppression or enhancement (Ref.**  **9). Dissolved solids can deposit on the nebulizer tip of a pneumatic nebulizer and on the**  **interface skimmers (reducing the orifice size and t he instrument performance). Dissolved solid**  **levels below 0.2% (2,000 mg/L) have been currently recommended (Ref. 10) to minimize solid**  **deposition, although currently-available ICP-MS sys tems may be able to tolerate much higher** 

**levels. An internal standard can be used to correc t for physical interferences, if it is carefully**  **matched to the analyte so that the two elements are similarly affected by matrix changes (Ref.**  **11). When intolerable physical interferences are p resent in a sample, a significant suppression**  **of the internal standard signals (to less than 30% of the signals in the calibrations standard) will**  **be observed. Dilution of the sample five-fold (i.e. , dilute one part sample with four parts diluent**  **[1:5 = 1+4]) will usually eliminate the problem.**

**4.7 Memory interferences or carry-over can occur w hen there are large concentration**  **differences between samples or standards which are analyzed sequentially. Sample deposition**  **on the sampler and skimmer cones, spray chamber des ign, and the type of nebulizer affect the**  **extent of the memory interferences which are observ ed. The rinse period between samples**  **must be long enough to eliminate significant memory interference.** **SW-846 Update V 6020B - 7 Revision 2**  **July 2014 4.8 Reagents and sample processing hardware may yi**  **eld artifacts and/or interferences to sample analysis. All of these materials must be**  **demonstrated to be free from interferences under the conditions of the analysis by analyzing m**  **ethod blanks. Specific selection of reagents may be necessary. Refer to each method to be used**  **for specific guidance on QC procedures.**

**5.0 SAFETY**

**5.1 This method does not address all safety issues associated with its use. The**  **laboratory is responsible for maintaining a safe wo rk environment and a current awareness file**  **of OSHA regulations regarding the safe handling of the chemicals specified in this method. A**  **reference file of material safety data sheets (MSDS s) should be available to all personnel**  **involved in these analyses.**

**5.2 Concentrated nitric and hydrochloric acids are moderately toxic and extremely**  **irritating to skin and mucus membranes. Use these reagents in a hood and if eye or skin**  **contact occurs, flush with large volumes of water. Always wear safety glasses or a shield for**  **eye protection when working with these reagents.**

**5.3** Hydrofluoric acid is a very toxic acid and penetrat es the skin and tissues deeply if not treated immediately. **Injury occurs in two stages: firstly, by hydrati on that**  **induces tissue necrosis; and secondly, by penetrati on of fluoride ions deep into the tissue and**  **thereby reacting with calcium. Boric acid and/or o ther complexing reagents and appropriate**  **treatment agents should be administered immediately**

**.**

**WARNING : Consult appropriate safety literature for determ**  **ining the proper protective eyewear,**

**clothing and gloves to use when handling hydrofluor ic acid.**  Always have appropriate treatment materials readily available p rior to working with this

acid. **See Method 3052 for additional recommendations fo r handling hydrofluoric**  **acid from a safety and an instrument standpoint.**

**5.4 Many metal salts, are extremely toxic if inhal ed or swallowed.** 

**WARNING : Exercise extreme care to ensure that samples and**  **standards are handled safely**

**and properly and that all exhaust gases are properl y vented. Wash hands**  **thoroughly after handling.**

**6.0 EQUIPMENT AND SUPPLIES**

**6.1 Inductively coupled plasma-mass spectrometer:**

**6.1.1 The system must be capable of providing reso lution, better than or equal**  **to 1.0 u (unified atomic mass unit) at 10% peak hei ght. The system must have a mass**  **range from at least 6 to 240 u and a data system th at allows corrections for isobaric**  **interferences and the application of the internal s tandard technique. Use of a mass-flow**  **controller for the nebulizer argon and a peristalti c pump for the sample solution are** 

**recommended. SW-846 Update V 6020B - 8**  **Revision 2 July 2014**  **6.1.2 Argon gas, high-purity grade (99.99%).**

**6.2 Volumetric flasks of suitable material composi tion, precision and accuracy** 

**6.3 Volumetric pipets of suitable material composi tion, precision and accuracy** 

**This section does not list all common laboratory w are (e.g., beakers) that might be used.** 

**7.0 REAGENTS AND STANDARDS**

**7.1 Reagent-grade, and whenever necessary, ultra-h igh purity-grade chemicals, must**  **be used in all tests. Unless otherwise indicated, it is intended that all reagents conform to the**  **specifications of the Committee on Analytical Reage nts of the American Chemical Society,**  **where such specifications are available. Other gra des may be used, provided it is first**  **ascertained that the reagent is of sufficiently hig h purity to permit its use without lessening the**  **accuracy of the determination.**

**7.2 Reagent water - Reagent water must be interfer ence free. All references to water**  **in this method refer to reagent water unless otherw ise specified.** 

**7.3 Ultra high-purity or equivalent acids must be used in the preparation of standards**  **and for sample processing. Redistilled acids are r ecommended because of the high sensitivity**  **of ICP-MS. Nitric acid at less than 2% (v/v) is ne cessary for ICP-MS to minimize damage to the** 

**interface and to minimize isobaric molecular-ion in terferences with the analytes. Many more**  **molecular-ion interferences are observed when hydro chloric and sulfuric acids are used (Refs. 3**  **and 4). The use of 1% (v/v) HCl is necessary for t he stability of antimony and silver**  **concentrations in the range of 50 - 500 μg/L. For concentrations greater than 500 μg/L silver,**  **additional HCl will be needed. As a consequence, t he accuracy of analytes that need significant**  **chloride molecular-ion corrections (e.g., As and V) will degrade.** 

**7.3.1 Nitric acid (concentrated), HNO 3** 

**7.3.2 Nitric acid (50% [v/v]), HNO 3**  **- Prepare by adding 500 mL concentrated**

**HNO 3**  **to 400 mL water and diluting to 1 L.**

**7.3.3 Nitric acid (1% [v/v]), HNO 3**  **- Prepare by adding 10 mL concentrated**

**HNO 3**  **to 400 mL water and diluting to 1 L.**

**7.3.4 Hydrochloric acid (concentrated), HCl**

**7.3.5 Hydrochloric acid (37%), HCl - Prepare by ad ding 370 mL concentrated**  **HCl to 400 mL water and diluting to 1L.**

**7.3.6 Hydrofluoric acid (concentrated), HF**

**7.3.7 Phosphoric acid (concentrated), H 3**  **PO 4** **SW-846 Update V 6020B - 9 Revision 2**  **July 2014 7.3.8 Phosphoric acid (85% [v/v]), H**  **3 PO**  **4 - Prepare by adding 850 mL** 

**concentrated H 3**  **PO 4**  **to 100 mL water and diluting to 1 L.**

**7.3.9 Sulfuric acid (concentrated), H 2**  **SO 4** 

**7.3.10 Sulfuric acid (96% [v/v]) H 2**  **SO 4**  **, - Prepare by adding 40 mL water to a 2 L glass beaker. While gently stirring, carefully add**  **960 mL concentrated H 2**  **SO 4**  **to the**

**beaker. Mix until combined. Allow to cool. Caref ully, quantitatively transfer solution to a**  **1-L volumetric flask. Bring to volume with additio nal water if necessary. Mix thoroughly**  **through inversion to combine.**

**WARNING : Considerable heat is generated upon combining sul**  **furic acid and water. The use of appropriate personal protection (e.g. proper**  **gloves, safety glasses and protective clothing) is necessary to avoid personal injury suc**  **h as thermal burns or acid burns due to solution splatter. Also, always add acid to water**  **(rather than water to acid) to reduce splatter.** 

**7.3.11 Citric acid, HO 2**  **CCH 2**  **C(OH)(CO 2**  **H)CH 2**  **CO 2**  **H**

**7.4 Bismuth(III) oxide, Bi 2**  **O 3** 

**7.5 Holmium(III) carbonate pentahydrate, Ho 2**  **(CO 3**  **) 3**  **•5H 2**  **O**

**7.6 Indium (powder), In**

**7.7 Lithium[ 6**  **Li] carbonate (95 atom % 6**  **Li), 6**  **Li 2**  **CO 3** 

**7.8 Ammonium hexachlororhodate(III), (NH 4**  **) 3**  **RhCl 6** 

**7.9 Scandium(III) oxide, Sc 2**  **O 3** 

**7.10 Terbium(III) carbonate pentahydrate, Tb 2**  **(CO 3**  **) 3**  **•5H 2**  **O**

**7.11 Yttrium(III) carbonate, Y 2**  **(CO 3**  **) 3**  **•3H 2**  **O**

**7.12 Ammonium hexafluorotitanate(IV), (NH 4**  **) 2**  **TiF 6** 

**7.13 Ammonium molybdate(VI) (NH 4**  **) 2**  **MoO 4** 

**7.14 Aluminum(III) nitrate nonahydrate, Al(NO 3**  **) 3**  **•9H 2**  **O**

**7.15 Calcium carbonate, CaCO 3** 

**7.16 Iron powder, Fe**

**7.17 Magnesium oxide, MgO**

**7.18 Sodium carbonate, Na 2**  **CO 3** **SW-846 Update V 6020B - 10 Revision 2**  **July 2014 7.19 Potassium carbonate, K**  **2 CO**  **3**

**7.20 Standard stock solutions - Purchase standard stock solutions from an appropriate**  **commercial source. Otherwise, prepare them manuall y in the laboratory using only ultra, high**  **purity grade chemicals or metals (** ≥ **99.99% purity). See Method 6010 for instructions on**  **preparing standard solutions from solids. Replace stock standards when succeeding dilutions**  **for the preparation of calibration standards cannot be verified.** 

**7.20.1 Bismuth internal standard stock solution (1 00 μg/mL Bi) - Dissolve**  **0.1115 g Bi 2**  **O 3**  **in a minimum amount of dilute HNO 3**  **. Add 10 mL concentrated HNO 3**  **and dilute to 1 L with reagent water.** 

**7.20.2 Holmium internal standard stock solution (1 00 μg/mL Ho) - Dissolve**  **0.1757 g Ho 2**  **(CO 3**  **) 3**  **•5H 2**  **O in 10 mL reagent water and 10 mL concentrated HNO 3**  **. After dissolution is complete, warm the solution to degas**  **. Add 10 mL concentrated HNO 3**  **and dilute to 1 L with reagent water.** 

**7.20.3 Indium internal standard stock solution (10 0 μg/mL In)** 
- **Dissolve 0.1000 g**

**indium in 10 mL concentrated HNO 3**  **. Dilute to 1 L with reagent water.**

**7.20.4 Lithium internal standard stock solution (1 00 μg/mL**  **6 Li)** 
- **Dissolve 0.6312 g**  **6 Li**  **2 CO**  **3 (95% atomic abundance) in 10 mL of reagent water a**  **nd 10 mL**

**concentrated HNO 3**  **. After dissolution is complete, warm the solution to degas. Add** 

**10 mL concentrated HNO 3**  **and dilute to 1 L with reagent water.**

**7.20.5 Rhodium internal standard stock solution (1 00 μg/mL Rh)** 
- **Dissolve 0.3593 g (NH**  **4 )**  **3 RhCl**  **6 in 10 mL reagent water. Add 100 mL concentrated H**  **Cl and dilute to 1 L with reagent water.** 

**7.20.6 Scandium internal standard stock solution ( 100 μg/mL Sc)** 
- **Dissolve 0.15343 g Sc**  **2 O**  **3 in 10 mL 50% hot HNO**  **3 . Add 5 mL concentrated HNO**  **3 and dilute to 1 L**  **with reagent water.**

**7.20.7 Terbium internal standard stock solution (1 00 μg/mL Tb)** 
- **Dissolve 0.1828 g Tb**  **2 (CO**  **3 )**  **3 •5H**  **2 O in 10 mL 50% HNO**  **3 . After dissolution is complete, warm the**  **solution to degas. Add 5 mL concentrated HNO 3**  **and dilute to 1 L with reagent water.**

**7.20.8 Yttrium internal standard stock solution (1 00 μg/mL Y)** 
- **Dissolve 0.2316 g**

**Y 2**  **(CO 3**  **) 3**  **•3H 2**  **O in 10 mL 50% HNO 3**  **. Add 5 mL concentrated HNO 3**  **and dilute to 1 L with reagent water.** 

**7.20.9 Titanium interference stock solution (100 μ g/mL Ti)** 
- **Dissolve 0.4133 g (NH**  **4 )**  **2 TiF**  **6 in reagent water. Add 2 drops concentrated HF and**  **dilute to 1 L with reagent**

**water.**

**7.20.10 Molybdenum interference stock solution (10 0 μg/mL Mo)** 

**- Dissolve**  **0.2043 g (NH 4**  **) 2**  **MoO 4**  **in reagent water. Dilute to 1 L with reagent wate r.** **SW-846 Update V 6020B - 11 Revision 2**  **July 2014 7.20.11 Gold preservative stock solution for merc**  **ury (100 μg/mL Au) - Purchase**  **as a commercially prepared, high-purity solution of AuCl**  **3 in dilute HCl matrix.** 

**7.21 Mixed-calibration standard solutions - Prepare by diluting stock standard solutions**  **to levels in the linear range for the instrument, u sing the same combination and concentrations**  **of acids used in the preparation of the sample dige states (approximately 1% HNO**  **3 ). The** 

**calibration standard solutions must contain a suita ble concentration of an appropriate internal**  **standard for each analyte. Internal standards may be added on-line at the time of analysis**  **using a second channel of the peristaltic pump and an appropriate mixing manifold. Generally,** 

**an internal standard should be no more than 50 u re moved from the analyte. Recommended** 

**internal standards include 6**  **Li, 45**  **Sc, 89**  **Y, 103**  **Rh, 115**  **In, 159**  **Tb, 169**  **Ho, and 209**  **Bi. Prior to preparing the mixed standards, each stock standard solution m**  **ust be analyzed separately to determine possible spectral interferences or the presence of**  **impurities.**

**NOTE : Care should be taken when preparing the calibrat**  **ion standards to ensure that the elements are compatible and stable when mixed toget**  **her. Standards which interfere with another analyte, or which are contaminated wit**  **h another analyte, may not be**

**included in the same calibration standard as that a nalyte.** 

**Transfer the mixed-standard solutions to an appropr iate container for storage. Freshly mixed**  **standards must be prepared as needed with the reali zation that concentrations can change**  **upon aging. Calibration standards must be initiall y verified using a QC standard (see Sec.**  **7.24).**

**7.22 Blanks - Three types of blanks are necessary for analysis:**  **(1) the calibration blank, which is used in establishing the calibratio**  **n curve; (2) the method blank, which is used to monitor for possible contamination resulting from t**  **he sample preparation procedure; and (3) the rinse blank, which is used to flush the system betw**  **een all samples and standards.**

**7.22.1 Calibration blank - Prepare by acidifying re agent water using the same** 

**combination and concentrations of acids used in the preparation of the matrix-matched**  **calibration standards (Sec. 7.21) along with the se lected concentrations of internal**  **standards, such that there is an appropriate intern al standard element for each of the**  **target analytes. The use of HCl for antimony and s ilver is discussed in Sec. 7.3. The** 

**calibration blank will also be used for all initial calibration blank (ICB) and continuing**  **calibration blank (CCB) determinations.**

**7.22.2 Method blank — Prepare by a processing eith er a volume of reagent**  **water equal to that used for actual aqueous samples , or, otherwise, a clean, empty**  **container, equivalent to that used for actual solid samples through all of the preparatory**  **and instrument determination steps used for making ICP-MS determinations in samples.**  **These steps may include, but are not limited to, pr e-filtering, digestion, dilution, filtering,**  **and analysis (refer to Sec. 9.5).**

**7.22.3 Rinse blank - Prepare as a 1 - 2% HNO 3**  **solution. Prepare a sufficient quantity such that it may be used to flush the syst**  **em in between standards and samples. If mercury is to be analyzed, the rinse blank shoul**  **d also contain 2 μg/mL AuCl 3** 

**. SW-846 Update V 6020B - 12**  **Revision 2 July 2014**  **7.23 Spectral interference check (SIC) solutions - Prepare so as to contain known**  **concentrations of interfering elements that will de monstrate the appropriate magnitude of**  **interferences and provide an adequate test of any c orrections. Chloride in the SIC solution**  **provides a means to evaluate software corrections f or chloride-related interferences such as** 

**35 Cl**  **16 O**  **+ on**  **51 V**  **+ and**  **40 Ar**  **35 Cl**  **+ on**  **75 As**  **+ . Iron is used to demonstrate adequate resolution**  **of the spectrometer for the determination of manganese. M**  **olybdenum serves to indicate oxide effects on cadmium isotopes. The other components are pres**  **ent to evaluate the ability of the measurement system to correct for various molecular**  **-ion isobaric interferences. The SIC is used to verify that the interference levels are cor**  **rected by the data system within appropriate**
**QC limits.**

**NOTE : The final SIC solution concentrations in Table 1**  **are intended to evaluate corrections for known interferences on only the analytes identified**  **in Sec. 1.0. If the test method is to be used to determine other element(s), it is the re**  **sponsibility of the analyst to modify the SIC solution accordingly, or prepare an alterna**  **tive SIC solution, so as to allow adequate verification of interference corrections o**  **n the additional element(s) (see Sec. 9.9).** 

**7.23.1 Mixed stock SIC solutions - Prepare the SIC stock solutions using only**  **ultra-pure reagents. They can be obtained commerci ally or prepared using the following**  **procedures:**

**7.23.1.1 Mixed SIC stock solution I - Prepare by a dding 13.903 g**  **Al(NO 3**  **) 3**  **•9H 2**  **O, 2.498 g CaCO 3**  **(previously dried at 180** Ε **C for 1 hr), 1.000 g Fe, 1.658 g MgO, 2.305 g Na**  **2 CO**  **3 and 1.767 g K**  **2 CO**  **3 to 25 mL of reagent water.**  **Slowly add 40 mL of (50%) HNO 3**  **. After dissolution is complete, warm the solution to degas. Cool and dilute to 1 L with reagent wate**  **r.**

**7.23.1.2 Mixed SIC stock solution II - Prepare by slowly adding 7.444 g** 

**85% H 3**  **PO 4**  **, 6.373 g 96% H 2**  **SO 4**  **, 40.024 g 37% HCl, and 10.664 g citric acid (C**  **6 O**  **7 H**  **8 ) to 100 mL of reagent water. Dilute to 1 L with r**  **eagent water.**

**7.23.2 Mixed working SIC solution - Prepare by com bining 10.0 mL of SIC stock**  **solution I, 2.0 mL each of 100-μg/mL titanium stock solution and 100-μg/mL molybdenum**  **stock solution, and 5.0 mL of SIC stock solution II . Dilute to 100 mL with reagent water.**  **Prepare fresh weekly.**

**7.24 Initial calibration verification (ICV) standa rd - Prepare by combining compatible** 

**metals from standard stock solution sources that di ffer from those used for the preparation of**  **the calibration standards. The ICV should be prepa red so as to contain metal concentrations**  **that are near, but not equal to, the midpoint conce ntration level of the calibration curve.** 

**7.25 Continuing calibration verification (CCV) sta ndard - Prepare using the same acid**  **matrix and stock standards employed when preparing the calibration standards. The CCV**  **should be prepared so as to contain metal concentra tions equal or nearly equivalent to the**  **midpoint concentration of the calibration curve.**

**7.26 Mass spectrometer tuning solution - Prepare s o as to contain elements that**  **represent all of the mass regions of interest (i.e. , 10 μg/L Li, Co, In, and Tl) in order to verify th**  **at SW-846 Update V 6020B - 13**  **Revision 2 July 2014**  **the resolution and mass calibration of the instrume nt are within the designated specifications**  **(see Sec. 10.1).**

**7.27 If the determination of one or more metals usi ng a non-aqueous solvent is**  **required, then all standards and quality control sa mples must be prepared on a weight/weight**  **basis in the non-aqueous solvent since the density of non-aqueous solvents is not uniform.**  **Standards and quality control materials containing organometallic materials that are soluble in**  **non-aqueous solvents are available from a variety o f vendors.** 

**8.0 SAMPLE COLLECTION, PRESERVATION, AND STORAGE**

**Sample collection, preservation and storage require ments may vary by EPA program and**  **may be specified in a regulation or project plannin g document that requires compliance**  **monitoring for a given contaminant. Where such req uirements are specified in the regulation,**  **follow those requirements. In the absence of speci fic regulatory requirements, use the following**  **information as guidance in determining the sample c ollection, preservation and storage**  **requirements.**

**See Chapter Three, Inorganic Analytes, for sample c ollection and preservation** 

**instructions.**

**9.0 QUALITY CONTROL**

**9.1 Refer to Chapter One for guidance on quality as surance (QA) and QC protocols.**  **When inconsistencies exist between QC guidelines, m ethod-specific QC criteria take**  **precedence over those criteria given in Chapter One . Any effort involving the collection of**  **analytical data should include development of a str uctured and systematic planning document,**  **such as a Quality Assurance Project Plan (QAPP) or a Sampling and Analysis Plan (SAP),**  **which translates project objectives and specificati ons into directions for those that will implement**  **the project and assess the results. Each laborator y should maintain a formal quality assurance**  **program. The laboratory should also maintain recor ds to document the quality of the data**  **generated. All data sheets and QC data should be m aintained for reference or inspection.** 

**9.2 Refer to Methods 3005, 3010, 3015, 3031, 3040, 3050, 3051, 3052, 7000, and**  **6800 for QC procedures to ensure the proper operati on of the various sample preparation**  **techniques. Any more specific QC procedures provid ed in this method will supersede those**  **noted in Methods 3005, 3010, 3015, 3031, 3040, 3050 , 3051, 3052, 7000, and 6800.** 

**9.3 Instrument Detection Limits**

**Instrument detection limits (IDLs) are useful means to evaluate the instrument noise level**  **and response changes over time for each analyte fro m a series of reagent blank analyses to**  **obtain a calculated concentration. They are not to be confused with the lower limit of**  **quantitation, nor should they be used in establishi ng this limit. It may be helpful to compare the**  **calculated IDLs to the established lower limit of q uantitation, however, it should be understood**  **that the lower limit of quantitation needs to be ve rified according to the guidance in Sec. 9.8.**  **IDLs in μg/L can be estimated as the mean of the bl ank result plus three times the standard** **SW-846 Update V 6020B - 14 Revision 2**  **July 2014 deviation of 10 replicate analyses of the reagent b**  **lank solution. (Use zero for the mean if the mean is negative). Each measurement should be perfo**  **rmed as though it were a separate analytical sample (i.e., each measurement must be f**  **ollowed by a rinse and/or any other procedure normally performed between the analysis o**  **f separate samples). IDLs should be determined at least once using new equipment, after**  **major instrument maintenance such as changing the detector, and/or at a frequency design**  **ated by the project. An instrument log book should be kept with the dates and information perta**  **ining to each IDL performed.**

**9.4 Initial demonstration of proficiency**

**Each laboratory must demonstrate initial proficienc y with each sample preparation and**  **determinative method combination by generating data of acceptable precision and bias for**  **target analytes in a clean matrix. If an autosampl er is used to perform sample dilutions, before**  **using the autosampler to dilute samples, the labora tory should satisfy itself that those dilutions**  **are of equivalent or better accuracy than is achiev ed by an experienced analyst performing** 

**manual dilutions. It is recommended that the labor atory should repeat the demonstration of**  **proficiency whenever new staff members are trained or significant changes in instrumentation** 

**are made.**

**9.5 Initially, before processing any samples, the a nalyst should demonstrate that all**  **parts of the equipment that come into direct contac t with the sample and reagents are**  **interference-free. This is accomplished through th e analysis of a method blank. As a**  **continuing check, each time samples are digested an d analyzed, and when there is a change in**  **reagents, a method blank should be prepared and ana lyzed for the compounds of interest as a**  **safeguard against chronic laboratory contamination. If an interference is observed that would**  **prevent the determination of the target analyte, de termine the source and eliminate it, if**  **possible, before processing the samples. The metho d blank should be carried through all**  **stages of sample preparation and instrument determi nation procedures. When new reagents or**  **chemicals are received, the laboratory should monit or the preparation and/or analysis blanks**  **associated with samples for any signs of contaminat ion. It is not necessary to test every new**  **batch of reagents or chemicals prior to sample prep aration if the source shows no prior**  **problems. However, if reagents are changed during a preparation batch, separate blanks need**  **to be prepared for each set of reagents.**

**9.6 Linear range**

**The linear range establishes the highest concentrat ion that may be reported without**  **diluting the sample. Following calibration, the lab oratory may choose to analyze a standard at a**  **higher concentration than the high standard in the calibration. The standard must recover within**  **10% of the true value, and if successful, establish es the linear range. The linear range**  **standards must be analyzed in the same instrument r un as the calibration they are associated**  **with (i.e., on a daily basis) but may be analyzed a nywhere within that run. If a linear range**  **standard is not analyzed for any specific element, the highest standard in the calibration**  **becomes the linear range.**

**9.7 Sample QC for preparation and analysis**

**The laboratory must also have procedures for docum enting the effect of the matrix on**  **method performance (precision, bias, and sensitivit y). At a minimum, this should include the** **SW-846 Update V 6020B - 15 Revision 2**  **July 2014 analysis of QC samples including a method blank, a**  **matrix spike (MS), a laboratory control sample (LCS), and a duplicate sample in each analyt**  **ical batch. Any method blanks, LCS, MS samples, and duplicate samples should be subjected**  **to the same preparatory and instrument determination procedures as those used on actual sa**  **mples (see Sec. 11.0).**

**9.7.1 For each batch of samples analyzed, at least one method blank must be**  **carried throughout the entire sample preparation an d instrument determination process, as**  **described in Chapter One. The importance of the me thod blank is to aid in identifying**  **when and/or if sample contamination is occurring. The method blank is considered to be**  **acceptable if it does not contain the target analyt es at concentration levels that exceed the**  **acceptance limits defined in Chapter One or in the project-specific DQOs. The laboratory** 

**should not subtract the results of the method blank from those of any associated samples.** 

**Such "blank subtraction" is not reliable because it is based on a single method blank value**  **rather than a statistically determined blank concen tration.** 

**Blanks are generally considered to be acceptable if target analyte concentrations**  **are less than 1⁄2 the LLOQ or are less than project-s pecific requirements. Blanks may**  **contain analyte concentrations greater than accepta nce limits if the associated samples in**  **the batch are unaffected (i.e. targets are not pres ent in samples or sample concentrations** 

are ≥10X

**the blank). Other criteria may be used depending o n the needs of the project.** 

**If the method blank fails to meet the necessary acc eptance criteria, it should be re**  **analyzed once. If still unacceptable, then all sam ples associated with the method blank**  **must be re-prepared and re-analyzed, along with all other appropriate analysis batch QC**  **samples. If the method blank results do not meet t he acceptance criteria and reanalysis**  **is not practical, then the laboratory should report the sample results along with the**  **method blank results, and provide a discussion of t he potential impact of the**  **contamination on the sample results. However, if a n analyte of interest is found in a**  **sample in the batch near its concentration confirme d in the blank, the presence and/or**  **concentration of that analyte should be considered suspect and may require**  **qualification. Refer to Chapter One for additional guidance regarding the proper protocol**  **when analyzing method blanks.**

**9.7.2 Documenting the effect of the matrix should include the analysis of at**  **least one MS and one duplicate unspiked sample or o ne matrix spike/matrix spike**  **duplicate (MS/MSD) pair for each batch of samples p rocessed, at a minimum frequency of**  **one per every 20 samples, as described in Chapter O ne. An MS/MSD pair is used to**  **document the bias and precision of a method in a gi ven sample matrix. The decision on**  **whether to prepare and analyze duplicate samples or an MS/MSD pair must be based on**  **knowledge of the samples in the analysis batch. If samples are expected to contain target**  **analytes above the LLOQ, laboratories may choose to use an MS and a duplicate analysis**  **of an unspiked field sample. If samples are not ex pected to contain target analytes above**  **the LLOQ, the laboratories should use an MS/MSD pai r.** 

**MS/MSD samples should be spiked with each target e lement at the project-specific**  **action levels, or, when lacking project-specific ac tion levels, between the low- and mid**  **level standards, as appropriate. Acceptance criter ia should be set at laboratory-derived**  **limits, developed through the use of historical ana lyses, for each matrix type being**  **analyzed. However, historically derived acceptance limits must not exceed ± 25%** **SW-846 Update V 6020B - 16 Revision 2**  **July 2014 recovery of the target element spike values for bia**  **s, and ≤ 20 relative percent difference (RPD) for precision. In the absence of historical**  **data, MS/MSD acceptance limits should be set at ± 25% recovery and ≤ 20 RPD. Refer to Se**  **c. 4.0 of Chapter One for further guidance. If the bias and precision indicators in**  **an analytical batch fail to meet the acceptance criteria, then the interference test dis**  **cussed in Sec. 9.10 should be performed. Refer to the definitions of bias and precision, in**  **Chapter One, for the proper data reduction protocols.** 

**NOTE : If the background sample concentration is very l**  **ow or non-detect, a spike of greater than 5 times the background concentration i**  **s still acceptable. To assess data precision with duplicate analyses, it is prefe**  **rable to use a high concentration field sample to prepare unspiked laboratory duplica**  **tes for metals analyses.**

**Calculate the RPD between duplicate or MS determin ations as follows:** 

**100**

**2 D**  **D D**  **D RPD** 

**2**

**1 2**  **1** ×

        + −

=

**where:**

**RPD = relative percent difference**

**D 1**  **= MS or first sample analysis value**

**D 2**  **= MSD or duplicate sample analysis value**

**9.7.3 At least one LCS should be prepared and anal yzed with each batch of**  **analytical samples processed, at a minimum frequenc y of one LCS per every 20 samples,**  **as described in Chapter One. The LCS consists of a n aliquot of a clean (control) matrix**  **similar to the sample matrix and of the same weight or volume. The LCS should be spiked**  **at the same levels and using the same spiking mater ials as the corresponding MS/MSD**  **(see above Sec. 9.7.2). When the results of the MS analysis indicate a potential problem**  **due to the sample matrix itself, the LCS results ar e used to verify that the laboratory can**  **acceptably perform the analysis in a clean matrix.**

**LCS acceptance criteria should be set at laborator y-derived limits, developed through the**  **use of historical analyses. However, historically derived acceptance limits must not**  **exceed ± 20% of the target element spike values. I n the absence of historical data, LCS**  **acceptance limits should be set at ± 20%. If the r esult of an LCS does not meet the**  **established acceptance criteria, it should be re-an alyzed once. If still unacceptable, then**  **all samples associated with the LCS must be re-prep ared and re-analyzed, along with all**  **other appropriate analysis batch QC samples.**

**9.7.4 Reference materials containing known amounts of target elements are**  **recommended when an appropriately similar medium of interest are available as one type**  **of QC after appropriate sample preparation. The re ference material may be used as the**  **LCS. For soil reference materials, the manufacture rs’ established acceptance criterion**  **should be used. For solid reference materials, ± 2 0% (see Sec. 9.7.3) recovery of the**  **reported manufacturers’ target element values may n ot be achievable. Refer to Chapters** 

**One and Three for additional information. SW-846 Update V 6020B - 17**  **Revision 2 July 2014**  **9.8 Lower Limit of Quantitation (LLOQ) check stand ard** 

**9.8.1 The laboratory should establish the LLOQ as t he lowest point of**  **quantitation which, in most cases, is the lowest co ncentration in the calibration curve. The**  **LLOQ is initially verified by the analysis of at le ast 7 replicate samples, spiked at the LLOQ**  **and processed through all preparation and analysis steps of the method. The mean**  **recovery and relative standard deviation of these s amples provide an initial statement of**  **precision and accuracy at the LLOQ. In most cases t he mean recovery should be +/- 35%** 

**of the true value and RSD should be < 20%. In-house limits may be calculated when**  **sufficient data points exist. Monitoring recovery o f LLOQ over time is useful for assessing**  **precision and bias. Refer to a scientifically valid and published method such as Chapter 9**  **of Quality Assurance of Chemical Measurements (Tayl or 1987) or the Report of the**  **Federal Advisory Committee on Detection and Quantit ation Approaches and Uses in**  **Clean Water Act Programs (http://water.epa.gov/scit ech/methods/cwa/det/index.cfm**  **) for calculating precision and bias for LLOQ.** 

**9.8.2 Ongoing LLOQ verification, at a minimum, is o n a quarterly basis to**  **validate quantitation capability at low analyte con centration levels. This verification may**  **be accomplished either with clean control material (e.g., reagent water, method blanks,**  **Ottawa sand, diatomaceous earth, etc.) or a represe ntative sample matrix (free of target**  **compounds). Optimally, the LLOQ should be less tha n the desired regulatory action levels**  **based on the stated project-specific requirements.**

**9.9 Verify the magnitude of elemental and molecula r-ion isobaric interferences and the**  **adequacy of any corrections at the beginning of an analytical run or once every 12 hours of**  **continuing sample analysis, whichever is more frequ ent. Do this by analyzing the SIC solution.**  **Results for the unspiked elements in the SIC soluti on should be less than 2 times the LLOQ.**  **Note that it may not be possible to obtain SIC spik ing solutions that are completely free of the**  **unspiked elements. If the presence and concentratio n of an unspiked element can be confirmed** 

**via vendor documentation and/or determination of mu ltiple isotopes of the element in the correct**  **ratios, the concentration actually present may be s ubtracted from the determined value prior to**  **comparing to the LLOQ limits. Refer to Sec. 4.0 fo r a discussion on interferences and potential**  **solutions to those interferences if additional guid ance is needed.** 

**9.10 The intensities of each internal standard mus t be monitored for every analysis to**  **ensure that it does not decrease below 30%, with re spect to its intensity during the initial**  **calibration. If this occurs, a significant matrix effect must be suspected. Under these**  **conditions, the IDL has degraded, and therefore the correction capability of the internal**  **standardization technique must then be questioned. If this happens, perform the following**  **procedure:**

**9.10.1 Make sure the instrument has not drifted by observing the internal**  **standard intensities in the nearest clean matrix, i .e., the calibration blank. If the low** 

**internal standard intensities are also observed in the nearby calibration blank, terminate**  **the analysis, correct the problem, recalibrate the instrument, verify the new calibration,**  **and reanalyze the affected samples.**

**9.10.2 If drift has not been demonstrated to occur as outlined in Sec. 9.10.1,**  **matrix effects need to be removed by diluting the a ffected sample. Dilute the sample five-** **SW-846 Update V 6020B - 18 Revision 2**  **July 2014 fold (1:5), taking into consideration the need to a**  **dd the appropriate amounts of internal standards, and reanalyze. If the first dilution do**  **es not eliminate the problem, repeat the dilution procedure in an iterative fashion, using e**  **ver-increasing dilutions, until the internal standard intensities exceed the 30% acceptance limi**  **t. Correct the reported results using the appropriate dilution factors.** 

**9.11 To obtain analyte data of known quality, it i s necessary to measure more than the**  **analytes of interest in order to apply corrections or to determine whether interference**  **corrections are necessary. For example, tungsten o xide molecular-ion species can be very**  **difficult to distinguish from mercury isotopes. If the concentrations of interference sources (such**  **as C, Cl, Mo, Zr, W) are such that, at the correcti on factor, the analyte is less than the LLOQ**  **and the concentration of interferents are insignifi cant, then the data may go uncorrected.** 

**NOTE : Monitoring the interference sources does not ine**  **vitably necessitate monitoring of the interferant itself, but that a molecular species ma**  **y be monitored to indicate the presence of the interferent.** 

**When correction equations are used, all QC criteri a must also be met. Extensive QC for** 

**interference corrections is needed at all times. T he monitored masses must include those**  **elements whose hydrogen, oxygen, hydroxyl, chlorine , nitrogen, carbon and sulfur molecular**  **ions could impact the analytes of interest. Unsusp ected interferences may be detected by**  **adding pure major matrix components to a sample to observe any impact on the analyte signals.**  **When an interference source is present, the sample elements impacted must be flagged to**  **indicate (a) the percentage interference correction applied to the data; or (b) an uncorrected**  **interference, by virtue of the elemental equation u sed for quantitation. The isotope proportions**  **for an element or molecular-ion cluster provide inf ormation useful for QA.** 

**NOTE : Only isobaric elemental, molecular, and doubly c**  **harged interference corrections, which employ the observed isotopic-response ratios or par**  **ent-to-oxide ratios (provided an**

**oxide internal standard is used as described in Sec . 4.2) for each instrument system,**  **are acceptable corrections for use in this method.**

**9.12 It is recommended that the laboratory adopt a dditional QA practices for use with**  **this method. The specific practices that are most productive depend upon the needs of the**  **laboratory and the nature of the samples. Whenever possible, the laboratory should analyze**  **reference materials and participate in relevant per formance evaluation (PE) studies.** 

**9.13 If less than acceptable bias and precision da ta are generated for the matrix**  **spike(s), the additional QC protocols in Sections 9 .13.1 and/or 9.13.2 should be performed prior**  **to reporting concentration data for the elements in this method. At a minimum these tests should**  **be performed with each batch of samples prepared/an alyzed with corresponding unacceptable**  **data quality results. If matrix interference effec ts are confirmed, then an alternative test method** 

**should be considered or the current test method mod ified, so that the analysis is not affected by** 

**the same interference. The use of a standard-additi on analysis procedure may also be used to**  **compensate for this effect (refer to Method 7000). SW-846 Update V 6020B - 19**  **Revision 2 July 2014**  **9.13.1 Dilution test**

**If the analyte concentration is within the linear range of the instrument and**  **sufficiently high (minimally, a factor of 25 times greater than the LLOQ), an analysis of a**  **1:5 dilution should agree to within ± 20% of the or iginal determination. If not, then a**  **chemical or physical interference effect must be su spected. The matrix spike is often a**  **good choice of sample for the dilution test, since reasonable concentrations of most**  **analytes are present. Elements that fail the diluti on test are reported as estimated values.** 

**9.13.2 Post-digestion MS**

**If a high concentration sample is not available fo r performing the dilution test, then**  **a post-digestion MS should be performed. The test o nly needs to be performed for the**  **specific elements that failed original matrix spike limits, and only if the spike concentration**  **added was greater than the concentration determined in the unspiked sample. Following**  **preparation, which may include, but is not limited to, pre-filtration, digestion, dilution and**  **filtration, an aliquot, or dilution thereof, should be obtained from the final aqueous,**  **unspiked-analytical sample, and spiked with a known quantity of target elements. The**  **spike addition should be based on the indigenous co ncentration of each element of**  **interest in the sample. The recovery of the post-d igestion MS should fall within a ± 25 %**  **acceptance range, relative to the known true value, or otherwise within the laboratory**  **derived acceptance limits. If the post-digestion M S recovery fails to meet the acceptance**  **criteria, the sample results must be reported as es timated values.** 

**9.14 Ultra-trace analysis necessitates the use of clean chemistry practices. Several**  **suggestions for the reduction of contaminants in th e analytical blank are provided in Chapter**  **Three, Inorganic Analytes.**

**10.0 CALIBRATION AND STANDARDIZATION**

**10.1 Conduct mass calibration and resolution verif ication checks in the mass regions of**  **interest using the mass spectrometer tuning solutio n (Sec. 7.26). The mass calibration and**  **resolution verification acceptance criteria must be met prior to the analysis of samples. If the**  **mass calibration differs by more than 0.1 u from th e true value, then the mass calibration must**  **be adjusted to the correct value. The resolution m ust also be verified to be less than 0.9 u full**  **width at 10% peak height.**

**10.2 At a minimum, the elements required for the p roject plus any required for** 

**interference correction must be calibrated. Recomme nded isotopes for the analytes in Sec. 1.2**  **are provided in Table 2. Flush the system in betwe en each standard and sample using the**  **rinse blank (Sec. 7.22.3). The rinse time needs to be sufficient to ensure that analytes present**  **in the linear range are effectively cleaned out pri or to analysis of the subsequent sample. Use**  **the average of at least three readings (of a single injection) for both calibration standard and**  **sample analyses.**

**10.3 Calibration standards should be prepared on an as-needed basis unless stability**  **warrants preparing fresh daily, (or each time a bat ch of samples is analyzed). If the ICV**  **standard is prepared daily and the results of the I CV analyses meet the acceptance criteria,** **SW-846 Update V 6020B - 20 Revision 2**  **July 2014 then the calibration standards do not need to be pr**  **epared daily and may be prepared and stored for as long as the calibration standard viab**  **ility can be verified through the use of the ICV. If the ICV fails to meet the acceptance criteria, t**  **rouble shoot the situation, and then prepare a**

**new set of calibration standards if needed and reca librate the instrument** 

**10.4 A calibration curve must be analyzed daily. Th e instrument may be calibrated**  **using a single point standard and a calibration bla nk (ICB) or a multipoint calibration curve. If a**  **multipoint curve is used a minimum of three standar ds are required and the correlation**  **coefficient (r) should be > 0.995 or the coefficient of determination (r**  **2 ) should be >**  **0.990. Relative Standard Error may be used as an alternati**  **ve to r or r 2**  **, and should be < 20%. If a**  **multipoint calibration is used the low standard mus t be at or below the LLOQ.** 

**NOTE: Inversely weighted linear regressions or othe r methods may be used in order to**  **minimize curve fitting errors at the low end of the calibration curve.** 

**10.5 After the initial calibration is completed it is verified using several checks.** 

**10.5.1 Initial Calibration Verification (ICV) - The ICV is a standard prepared from** 

**a different source than the initial calibration sta ndards. It is analyzed at approximately the** 

**mid-level of the calibration and serves as a check that the initial calibration standards are**  **at the correct concentrations. The acceptance range is 90-110% of the true value.** 

**10.5.2 Low-level readback or verification - For a m ulti-point calibration, the low**  **level standard should quantitate to within 80-120% of the true value. For a single point**  **calibration, a standard from the same source as the calibration standard and at or below**  **the LLOQ is analyzed and should recover within 80-1 20% of the true value.** 

**10.5.3 Mid-level readback or verification - For a m ulti-point calibration, the mid**  **level standard should quantitate to within 90-110% of the true value. For a single point**  **calibration, a standard from the same source as the calibration standard and at the mid**  **point of the linear range is analyzed and should re cover within 90-110% of the true value.** 

**10.5.4 Initial Calibration blank (ICB) - If a multi -level calibration is used, an ICB is**  **analyzed immediately after the calibration (or afte r the ICV) and must not contain target**  **analytes above half the LLOQ. If a single point cal ibration is used, the calibration is forced**  **through the ICB, but a second ICB is analyzed as a check and must not contain target**  **analytes above half the LLOQ. If the ICB consistent ly has target analyte concentrations**  **greater than half the LLOQ, the LLOQ should be re-e valuated.** 

**NOTE : After cleaning the sampler and skimmer cones, im**  **proved performance in calibration stability has been observed by method users if the**  **instrument is exposed to the SIC solution. Improved performance has also been observ**  **ed if the instrument is allowed to rinse for 5 - 10 minutes before starting the calibr**  **ation process.**

**10.5.5 Verify the ongoing validity of the calibrat ion curve after every 10 samples,**  **and at the end of each analysis batch run, through the analysis of a CCV standard (Sec.**  **7.25) and a CCB (Sec. 7.22.1). For the curve to be considered valid the analysis result of** 

**the CCV standard must be within ± 10% of its true v alue and the CCB must not contain**  **target analytes above the LLOQ. If the calibration cannot be verified, sample analysis** **SW-846 Update V 6020B - 21 Revision 2**  **July 2014 must be discontinued, the cause of the problem dete**  **rmined and the instrument recalibrated. All samples following the last accep**  **table CCV standard must be reanalyzed Flow-injection systems may be used as long as they**  **can meet the performance criteria of**

**the method.**

**11.0 PROCEDURE**

**11.1 Preliminary treatment of most samples is nece ssary because of the complexity and**  **variability of sample matrices. Groundwater sample s which have been pre-filtered and acidified**  **will not need acid digestion. Samples which are no t digested must either use an internal**  **standard or be matrix-matched with the standards (i .e., acid concentrations should match).**  **Solubilization and digestion procedures are present ed in Chapter Three, Inorganic Analytes.** 

**NOTE : If mercury is to be analyzed, the digestion proc**  **edure must use mixed nitric and hydrochloric acids through all steps of the digesti**  **on. Mercury will be lost if the sample is digested when hydrochloric acid is not present.**  **If it has not already been added to the sample as a preservative, Au should be added to**  **give a final concentration of 2 mg/L (use 2.0 mL of gold preservative stock (Sec. 7**  **.20.11) per 100 mL of sample) to preserve the mercury and to prevent it from plating**  **out in the sample introduction system.** 

**11.2 Initiate an appropriate operating configurati on of the instrument computer**  **according to the instrument manufacturer's instruct ions.** 

**11.3 Set up the instrument with the proper operati ng parameters according to the** 

**instrument manufacturer's instructions.**

**11.4 Operating conditions**

**Tune the instrument by following the instructions provided by the instrument manufacturer.**  **Allow at least 30 minutes for the instrument to equ ilibrate before analyzing samples.** 

**NOTE : The instrument should have features that protect**  **it from high ion currents. If not, precautions must be taken to protect the detector.**  **A channel electron multiplier or active film multiplier will suffer from fatigue aft**  **er being exposed to high ion currents. This fatigue can last from several seconds to hours**  **depending on the extent of exposure. During this time period, response factor**  **s are constantly changing, which invalidates the calibration curve, causes instabili**  **ty, and invalidates sample analyses.**

**11.5 Calibrate the instrument following the proced ure outlined in Sec. 10.0.** 

**11.6 Flush the system with the rinse blank soluti on (Sec. 7.22.3) until the signal levels**  **return to the data quality objectives or method LLO Qs (usually about 30 seconds) before the**  **analysis of each sample. Nebulize each sample unti l a steady-state signal is achieved (usually**  **about 30 seconds) prior to collecting data.**

**11.7 Dilute and reanalyze samples that exceed the linear range for an analyte (or**  **species needed for a correction) or measure an alte rnate, but less-abundant, isotope. The** **SW-846 Update V 6020B - 22 Revision 2**  **July 2014 linearity at the alternate mass must be confirmed b**  **y appropriate calibration (see Sec. 10.4). Alternatively apply solid-phase chelation chromatog**  **raphy to eliminate the matrix as described in**

**Sec. 4.3.**

**11.8 Determination of percent dry weight**

**When sample results are to be calculated on a dry-w eight basis, a separate portion of**  **sample for this determination should be weighed out at the same time as the portion used for**  **analytical determination.**

**CAUTION : The drying oven should be contained in a hood or**  **vented. Significant laboratory**

**contamination may result from a heavily contaminate d hazardous waste sample.** 

**11.8.1 Immediately after weighing the sample aliquo t to be digested, weigh an**  **additional 5- to 10-g aliquot of the sample to the nearest 0.01g into a tared crucible. Dry**  **this aliquot overnight at 105** Ε **C. Allow the sample to cool in a desiccator before weighing.** 

**11.8.2 Calculate the % dry weight as follows:**

**This oven-dried aliquot is not used for the extract ion and should be appropriately disposed**  **of once the dry weight is determined.**

**12.0 DATA ANALYSIS AND CALCULATIONS**

**12.1 If dilutions were performed, apply the approp riate corrections to the sample values.** 

**12.2 If appropriate, or required by the project or regulation for data reporting, calculate**  **results for solids on a dry-weight basis as follows :** 



### S W V C ion Concentrat DW 

### ×

×

=

**where:**

**Concentration DW**  **= Concentration on a dry weight basis (mg/kg)**

**C = Digest concentration (mg/L) V = Final volume after sample preparation (L)**  **W =Wet sample mass (kg) S = % Solids/100 = % dry weight/100** 

**Calculations must include appropriate interference corrections (see Sec. 4.2 for**  **examples), internal-standard normalization, and the summation of signals at 206, 207, and 208** 

m/z **for lead (to compensate for any differences in the abundances of these isotopes between**  **samples and standards). 100**  **x sample**  **of g**  **sample dry**  **of g**  **= weight**  **dry %** **SW-846 Update V 6020B - 23 Revision 2**  **July 2014 13.0 METHOD PERFORMANCE** 

**Performance data and related information are provid ed in SW-846 methods only as**  **examples and guidance. The data do not represent r equired performance criteria for users of**  **the methods. Instead, performance criteria should be developed on a project-specific basis,**  **and the laboratory should establish in-house QC per formance criteria for the application of this**  **method. These performance data are not intended to be and must not be used as absolute QC**  **acceptance criteria for purposes of laboratory accr editation.** 

**Table 3 summarizes the method performance data for aqueous and sea water samples with**  **interfering elements removed and samples preconcent rated prior to analysis. Table 4**  **summarizes the performance data for a simulated dri nking water standard. These data are**  **provided for guidance purposes only.**

**14.0 POLLUTION PREVENTION**

**14.1 Pollution prevention encompasses any techniqu e that reduces or eliminates the**  **quantity and/or toxicity of waste at the point of g eneration. Numerous opportunities for pollution**  **prevention exist in laboratory operations. The EPA has established a preferred hierarchy of**  **environmental management techniques that places pol lution prevention as the management**  **option of first choice. Whenever feasible, laborat ory personnel should use pollution prevention**  **techniques to address their waste generation. When wastes cannot be feasibly reduced at the**  **source, the Agency recommends recycling as the next best option.** 

**14.2 For information about pollution prevention th at may be applicable to laboratories** 

**and research institutions consult** Less is Better: Laboratory Chemical Management for Waste

Reduction **, a free publication available from the American Ch emical Society (ACS), Committee**  **on Chemical Safety, http://portal.acs.org/portal/fileFetch/C/WPCP_01229**  **0/pdf/WPCP_012290.pdf.**

**15.0 WASTE MANAGEMENT**

**The Environmental Protection Agency requires that laboratory waste management**  **practices be conducted consistent with all applicab le rules and regulations. The Agency urges**  **laboratories to protect the air, water, and land by minimizing and controlling all releases from**  **hoods and bench operations, complying with the lett er and spirit of any sewer discharge permits**  **and regulations, and by complying with all solid an d hazardous waste regulations, particularly** 

**the hazardous waste identification rules and land d isposal restrictions. For further information**  **on waste management, consult the ACS publication listed in Sec. 14.2.** **SW-846 Update V 6020B - 24 Revision 2**  **July 2014 16.0 REFERENCES** 

**1. Horlick, G., et al., Spectrochim. Acta 40B, 1555 (1985).** 

**2. Gray, A.L., Spectrochim. Acta 40B, 1525 (1985); 41B, 151 (1986).** 

**3. Tan, S.H., and Horlick, G., Appl. Spectrosc. 40, 445 (1986).** 

**4. Vaughan, M.A., and Horlick, G., Appl. Spectrosc. 40, 434 (1986).** 

**5. Holden, N.E., "Table of the Isotopes," in Lide, D.R., Ed., CRC Handbook of Chemistry and**  **Physics, 74th Ed., CRC Press, Boca Raton, FL, 1993.**

**6. Hinners, T.A., Heithmar, E., Rissmann, E., and S mith, D., Winter Conference on Plasma**  **Spectrochemistry, Abstract THP18; p. 237, San Diego , CA (1994).** 

**7. Lichte, F.E., et al., Anal. Chem. 59, 1150 (1987 ).** 

**8. Evans E.H., and Ebdon, L., J. Anal. At. Spectrom . 4, 299 (1989).** 

**9. Beauchemin, D., et al., Spectrochim. Acta 42B, 4 67 (1987).** 

**10. Houk, R.S., Anal. Chem. 58, 97A (1986).**

**11. Thompson, J.J., and Houk, R.S., Appl. Spectrosc . 41, 801 (1987).** 

**12. Newberry, W.R., Butler, L.C., Hurd, M.L., Laing , G.A., Stapanian, M.A., Aleckson, K.A.,**  **Dobb, D.E., Rowan, J.T., and Garner, F.C., Final Re port of the Multi-Laboratory**  **Evaluation of Method 6020 CLP-M Inductively Coupled Plasma-Mass Spectrometry**  **(1989).**

**13. Taylor, Daniel B., Kingston, H.M., Nogay, Donal d J., Koller, Dagmar, and Hutton, Robert.**  **On-Line Solid-phase Chelation for the Determination of Eight Metals in Environmental**  **Waters by Inductively Coupled Plasma Mass Spectrome try.** 

**14. Kingston, H. M., Siriraks, A., and Riviello, J. M., Patent Number 5,126,272, "A Method and**  **Apparatus for Detecting Transition and Rare Earth E lements in a Matrix", U.S. Patent,**  **Filed U.S. Patent Office, March 1989, 31 pages, Gra nted June 30, 1992, Patent held by** 

**US Government.**

**15. Kingston, H. M., Siriraks, A., and Riviello, J. M., Patent Number 5,244,634 , "A Method**  **and Apparatus for Detecting Transition and Rare Ear th Elements in a Matrix", U.S. Patent**  **, Filed U.S. Patent Office, March 1989, 31 pages, G ranted Sept. 14, 1993, Patent held by** 

**US Government.**

**16. Dobb, David E., Rowan, J.T., and Cardenas, D., Lockheed Environmental Systems and**  **Technologies Co., Las Vegas, NV; and Butler, L.C., and Heithmar, E.M., U.S.EPA, Las**  **Vegas, NV; Determination of Mercury by ICP-MS. SW-846 Update V 6020B - 25**  **Revision 2 July 2014**  **17. Taylor, J. K., “Quality Assurance of Chemical M easurements”, Lewis Publishers (1987).** 

**18. Federal Advisory Committee on Detection and Qua ntitation Approaches and Uses in**  **Clean Water Act Programs, Final Report, http://water.epa.gov/scitech/methods/cwa/det/index.**  **cfm (December 28, 2007).**

**17.0 TABLES, DIAGRAMS, FLOW CHARTS, AND VALIDATION DATA** 

**The pages to follow contain the tables, and figure s referenced by this method.** **SW-846 Update V 6020B - 26 Revision 2 July 2014**  **TABLE 1**

**RECOMMENDED SPECTRAL INTERFERENCE CHECK (SIC) SOLUT ION** 

**COMPONENTS AND CONCENTRATIONS**

**Solution Component**  **SIC Concentration (mg/L)** 

**Al 100.0**

**Ca 300.0**

**Fe 250.0**

**Mg 100.0**

**Na 250.0**

**P 100.0**

**K 100.0**

**S 100.0**

**C 200.0**

**Cl 2000.0**

**Mo 2.0**

**Ti 2.0 SW-846 Update V 6020B - 27 Revision 2**  **July 2014 TABLE 2** 

**RECOMMENDED ELEMENTAL ISOTOPES FOR SELECTED ELEMENT S** 

**Element of Interest Mass of Isotope**

**Aluminum** 27 **Antimony 121,**  123

**Arsenic** 75

**Barium 138, 137, 136,**  135 **, 134 Beryllium**  9 **Bismuth (IS) 209**

**Cadmium** 114 **, 112,** 111 **, 110, 113, 116, 106 Calcium (I)**  **42, 43,** 44 **, 46, 48 Chlorine (I) 35, 37, (77, 82)**  **a**

**Chromium** 52

**,** 53

**,** 50 **, 54**

**Cobalt** 59 **Copper** 63

**,** 65 **Holmium (IS) 165 Indium (IS)**  115 **, 113 Iron (I)**  56

**,** 54

**,** 57 **, 58 Lanthanum (I) 139** 

**Lead** 208

**,** 207

**,** 206 **, 204 Lithium (IS) 6**  **b , 7**  **Magnesium (I) 24,**  25

**,** 26 **Manganese** 55 **Mercury 202,**  200 **, 199, 201 Molybdenum (I)**  **98, 95, 96, 92,** 97 **, 94, (108) a** 

**Nickel 58,**  60 **, 62,** 61 **, 64 Potassium (I)**  39 **Rhodium (IS) 103 Scandium (IS) 45** 

**Selenium 80,**  78

**,** 82

**,** 76

**,** 77 **, 74**

**Silver** 107

**,** 109 **Sodium (I)** 23 **Terbium (IS) 159**

**Thallium** 205 **, 203**

**Vanadium** 51

**,** 50 **Tin (I) 120,**  118 **Yttrium (IS) 89**

**Zinc 64,**  66

**,** 68

**,** 67 **, 70**

**NOTE : Method 6020 is recommended for only those analyt**  **es listed in Sec.1.2. Other elements are included in this table because they are potential i**  **nterferents (labeled I) in the determination of recommended analytes, or because they are commonly**  **used internal standards (labeled IS). Isotopes are listed in descending order of natural**  **abundance. The most generally useful isotopes are underlined and in boldface, although certain ma**  **trices may necessitate the use of alternative isotopes.** 

**a These masses are also useful for interference corre**  **ction (Sec. 4.2).**

**b Internal standard must be enriched in the**  **6 Li isotope. This minimizes interference from indig**  **enous**
**lithium. SW-846 Update V** **6020B - 28 Revision 2** **July 2014 TABLE 3** **METHOD PERFORMANCE DATA FOR AQUEOUS AND SEA WATER S AMPLES** **a WITH INTERFERING ELEMENTS REMOVED AND SAMPLES PRECO** **NCENTRATED PRIOR TO ANALYSIS CONCENTRATION (ng/mL)** **b ELEMENT ISOTOPE 9.0 mL 27.0 mL CERTIFIED** **Manganese 55 1.8±0.05 1.9±0.2 1.99±0.15** **Nickel 58 0.32±0.018 0. 32±0.04 0.30±0.04** **Cobalt 59 0.033±0.002 0.028 ±0.003 0.025±0.006** **Copper 63 0.68±0.03 0.6 3±0.03 0.68±0.04** **Zinc 64 1.6±0.05 1. 8±0.15 1.97±0.12** **Copper 65 0.67±0.03 0 .6±0.05 0.68±0.04** **Zinc 66 1.6±0.06 1. 8±0.2 1.97±0.12** **Cadmium 112 0.020±0.0015 0. 019±0.0018 0.019±0.004** **Cadmium 114 0.020±0.0009 0. 019±0.002 0.019±0.004** **Lead 206 0.013±0.0009 0.019 ±0.0011 0.019±0.006** **Lead 207 0.014±0.0005 0.019 ±0.004 0.019±0.006** **Lead 208 0.014±0.0006 0.019 ±0.002 0.019±0.006** **NOTE : Data obtained from Ref. 12.** **a The dilution of the sea-water during the adjustment** **of pH produced 10 mL samples containing 9 mL of se a-water and 30 mL** **samples containing 27 mL of sea-water. Samples con taining 9.0 mL of CASS-2, n=5; samples containing 2** **7.0 mL of CASS-2, n=3.** **b 95% confidence limits** **SW-846 Update V 6020B - 29 Revision 2 July 2014**  **TABLE 4**

**ANALYSIS OF NIST SRM 1643b - TRACE METALS IN WATER a** 

**CONCENTRATION (ng/mL) b** 

**ELEMENT ISOTOPE DETERMINED CERTFIED**

**Manganese 55 30±1.3 28±2**

**Nickel 58 50±2 49±3**

**Cobalt 59 27±1.3 26±1**

**Nickel 60 51±2 49±3**

**Copper 63 23±1.0 21.9±0.4**

**Zinc 64 67±1.4 66±2**

**Copper 65 22±0.9 21.9±0.4**

**Zinc 66 67±1.8 66±2**

**Cadmium 111 20±0.5 20±1**

**Cadmium 112 19.9±0.3 20±1**

**Cadmium 114 19.8±0.4 20±1**

**Lead 206 23±0.5 23.7±0.7**

**Lead 207 23.9±0.4 23.7±0.7**

**Lead 208 24.2±0.4 23.7±0.7**

**NOTE : Data obtained from Ref. 12.** 

**a 5.0 mL samples, n=5** 

**b 95% confidence limits** **SW-846 Update V 6020B - 30 Revision 2 July 2014**  **TABLE 5**

**COMPARISON OF TOTAL MERCURY RESULTS IN HEAVILY CONT AMINATED SOILS** 

**Mercury in μg/g**

**Soil Sample ICP-MS CVAA**

**1 27.8**  **29.2**

**2 442**  **376**

**3 64.7**  **58.2**

**4 339**  **589**

**5 281**  **454**

**6 23.8**  **21.4**

**7 217**  **183**

**8 157**  **129**

**9 1670**  **1360**

**10 73.5**  **64.8**

**11 2090**  **1830**

**12 96.4**  **85.8**

**13 1080**  **1190**

**14 294**  **258**

**15 3300**  **2850**

**16 301**  **281**

**17 2130**  **2020**

**18 247**  **226**

**19 2630**  **2080**

**NOTE : Data obtained from Ref. 16.** **SW-846 Update V 6020B - 31 Revision 2 July 2014**  **METHOD 6020A**

**INDUCTIVELY COUPLED PLASMA - MASS SPECTROMETRY SW-846 Update V 6020B - 32 Revision 2**  **July 2014 Appendix A** 

**Summary of Revisions to Method 6020 (From Revision 1, February 2007):** 

**1. Improved overall method formatting for consisten cy with new SW-846 methods style**  **guidance. 2. Section 1.2 – Changed “Inductively coupled plasm**  **a—atomic emission spectrometry” to “Inductively coupled plasma—optical emission spectr**  **ometry”.**

**3. Section 1.6 - inserted references to additional 3000 series preparatory methods to ICP**  **analysis. Also added method 6800 to sections 1.6 an d 9.2 as a preparatory method.**  **4. Inserted additional safety guidance regarding th e use of HF.**  **5. Inserted new section (7.27) regarding analysis o f non-aqueous solvents.**  **6. Reformatted certain paragraphs with the heading "NOTE" or "WARNING" to better denote**  **the importance of the recommendations provided ther ein.**  **7. Extensively reformatted “REAGENTS AND STANDARDS” section and to meet current**  **SW-846 method guidelines. 8. Significantly updated and expanded “QUALITY CONT**  **ROL” section for better adherence to current SW-846 method guidelines and for improve**  **d alignment with current universal practices for published analytical methods.**  **9. Inserted new sections (Sections 7.23 and 9.9) to describe the preparation and use of the**  **spectral interference check (SIC) solution; also ad ded instructions to match the matrix of** 

**this solution to that of the calibration standards.**
**10. Renamed "QC standard" as "ICV standard" in Sec. 7.24.**  **11. Added new Sec. 7.25 describing the preparation of a "CCV" standard, consistent with the**  **equivalent section in 6010. 12. Replaced the term “unity” with “uniform” in Sec**  **tion 7.27. 13. Removed all references to method 7000 except fo**  **r guidance regarding the method of**

**standard addition. 14. The term “accuracy” was replaced by “bias” wher**  **e appropriate. 15. In Section 9.4, the requirement to repeat the d**  **emonstration of proficiency for new staff and instrumentation changes was changed to a recommenda**  **tion. 16. Section 9.7.2 – Added a note regarding MS/MSD s**  **pike concentrations and unspiked laboratory duplicates.**  **17. The section regarding analysis of reference mat erials (Sec. 9.7.4) was revised for clarity**  **and the term “Standard Reference Material” was repl aced with “reference material”**  **throughout the method. 18. Inserted new section (Sec. 9.8) describing the**  **preparation and use of an LLOQ standard. This section includes two new references for guidan**  **ce on assessing precision and bias. 19. The section describing matrix interference chec**  **k samples (Sec. 9.13) has been revised for clarity. The post-digestion MS is only recommended**  **if a high concentration sample is not available for performing the dilution test.**  **20. Substituted certain terms with new terms (i.e. “must” in place of “shall”) to conform with the**  **Performance-based Methods Approach goal of flexibil ity.**  **21. Removed reference to “linear dynamic range” as noted by the Inorganic Methods Work**  **Group. Section 9.6 regarding the linear range was a dded.** 

**22. Mid-level read back or verification standard ad ded to Section 10.5.3.**  **23. Moved the sentence “If the ICB consistently has target analyte concentrations greater than**  **half the LLOQ, the LLOQ should be re-evaluated.” Fr om Section 10.5.5 to Section 10.5.4.**  **24. Added 95 as mass of isotope for molybdenum. SW-846 Update V 6020B - 33 Revision 2**  **July 2014 25. Tables 3 and 4 from 6020A presenting example pr**  **ecision and accuracy data for aqueous**

**and solid matrices were removed. 26. Language was updated in Section 9.7.1 regarding**  **method blanks.**