1、Designation: D6800 12D6800 18Standard Practice forPreparation of Water Samples Using Reductive PrecipitationPreconcentration Technique for ICP-MS Analysis of TraceMetals1This standard is issued under the fixed designation D6800; the number immediately following the designation indicates the year ofo
2、riginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 Toxic elements may be present in ambient waters and may ent
3、er the food chain via uptake by plants and animals; the actualconcentrations of toxic metals are usually sub-ng/mL. The U.S. EPAhas published its Water Quality Standards in the U.S. FederalRegister 40 CFR 131.36, Minimum requirements for water quality standards submission, Ch. I (7-1-00 Edition), se
4、eAnnex, TableA1.1. The U.S. EPA has also developed Method 1640 to meet these requirements, see Annex, Table A1.2.1.2 Inductively Coupled Plasma Mass Spectroscopy (ICP-MS) is a technique with sufficient sensitivity to routinely measuretoxic elements in ambient waters, both fresh and saline (Test Meth
5、od D5673). However saline and hard water matrices poseanalytical challenges for direct multielement analysis by ICP-MS at the required sub-ng/mL levels.1.3 This standard practice describes a method used to prepare water samples for subsequent multielement analysis usingICP-MS. The practice is applic
6、able to seawater and fresh water matrices, which may be filtered or digested. Samples prepared bythis method have been analyzed by ICP-MS for the elements listed in Annex, Table A1.3).1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this
7、 standard.1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability ofregulatory limitations prio
8、r to use.1.6 This international standard was developed in accordance with internationally recognized principles on standardizationestablished in the Decision on Principles for the Development of International Standards, Guides and Recommendations issuedby the World Trade Organization Technical Barri
9、ers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D1129 Terminology Relating to WaterD1193 Specification for Reagent WaterD5673 Test Method for Elements in Water by Inductively Coupled PlasmaMass SpectrometryD5810 Guide for Spiking into Aqueous SamplesD5847 Practice for Writing
10、 Quality Control Specifications for Standard Test Methods for Water Analysis2.2 Other Documents:U.S. Federal Register 40 CFR 131.36, Minimum Requirements for Water Quality Standards Submission, Ch. I (7-1-00 Edition)3U.S. EPA Method 1640, Determination of Trace Elements in Water by Preconcentration
11、and Inductively Coupled Plasma-MassSpectrometry (1997)4U.S. EPA Method 1669, Sampling Ambient Water for Trace Metals at EPA Water Quality Criteria Levels41 This practice is under the jurisdiction of ASTM Committee D19 on Water and is the direct responsibility of Subcommittee D19.05 on Inorganic Cons
12、tituents in Water.Current edition approved March 1, 2012July 15, 2018. Published March 2012July 2018. Originally approved in 2002. Last previous edition approved in 20072012 asD6800 02 (2007)D68001. 12. DOI: 10.1520/D6800-12.10.1520/D6800-18.2 For referencedASTM standards, visit theASTM website, www
13、.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.3 Available from DODSSP, Bldg. 4, Section D,DLA Document Services, Building 4/D, 700 Robbins Ave., Philadelphia, PA 191
14、115098.19111-5094, http:/quicksearch.dla.mil.4 Available from United States Environmental ProtectionAgency (EPA),Ariel Rios William Jefferson Clinton Bldg., 1200 PennsylvaniaAve., NW, Washington, DC 20460,http:/www.epa.gov.This document is not an ASTM standard and is intended only to provide the use
15、r of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as
16、 published by ASTM is to be considered the official document.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13. Terminology3.1 DefinitionsDefinitions: For definitions of
17、 terms used in this test method refer to Terminology D1129.3.1.1 For definitions of terms used in this standard, refer to Terminology D1129.3.2 Definitions of Terms Specific to This Standard:3.2.1 continuing calibration blank, na solution containing no analytes (of interest) which is used to verify
18、blank response andfreedom from carryover.3.2.2 continuing calibration verification, na solution (or set of solutions) of known concentration used to verify freedom fromexcessive instrumental drift; the concentration is to cover the range of calibration curve.3.2.3 intermediate stock-standard solutio
19、n, na diluted solution prepared from one or more of the stock-standard solutions.3.2.4 laboratory control sample (LCS), nan aliquot of solution with known concentrations of method analytes.3.2.4.1 DiscussionThe LCS should be obtained from a reputable source or prepared at the laboratory from a separ
20、ate source from the calibrationstandards. The LCS is analyzed using the same sample preparation, analytical method and QA/QC procedure used for test samples.Its purpose is to determine whether method performance is within accepted control limits.3.2.5 laboratory duplicate (LD), na second sample aliq
21、uot that is analyzed using the same sample preparation, analyticalmethod and QA/QC procedure used for test samples.3.2.5.1 DiscussionThe purpose of the LD is to determine whether method performance is within accepted control limits.3.2.6 matrix spike (MS), na second sample aliquot to which known con
22、centrations of target analyte(s) are added in thelaboratory and which are analyzed using the same sample preparation and analytical method used for test samples.3.2.6.1 DiscussionThe purpose of the MS is to determine whether the sample matrix contributes bias to the analytical results. The backgroun
23、dconcentration of the matrix must be determined in a separate aliquot and the measured values in the MS corrected for theconcentrations found. Recommended spike levels are listed in Annex, Table A1.3.3.2.7 method blank (MB), nsuitable reagent-water aliquots that are analyzed using the same sample pr
24、eparation, analyticalmethod, and QA/QC procedure used for test samples.3.2.7.1 DiscussionThe MB is used to determine if method analytes or other interferences are present in the laboratory environment, the reagents orapparatus.3.2.8 method detection limit (MDL), na limit determined as described in t
25、he U.S. Federal Register (see 40 CFR Part 136,Appendix B).3.2.9 reagent water, nstandard laboratory water purified to meet Specification D1193 Type I or better.3.2.10 reporting detection limit (RDL), nthe lowest concentration at which an analyte can be reliably quantified.3.2.10.1 DiscussionThe RDL
26、represents the minimum concentration at which method performance becomes quantitative and is not subject to thedegree of variation observed at concentrations between the MDL and the RDL3.2.11 spiked blank (SB), na reagent-water aliquot to which known concentrations of analyte(s) are added in the lab
27、oratory,using the same solution as used to prepare the matrix spike.3.2.11.1 DiscussionThe spike blank is analyzed using the same sample preparation, analytical method and QA/QC procedure used for test samples.The purpose of the spike blank is to determine whether method performance is within accept
28、able limits. The spike blank is alsoD6800 182useful for troubleshooting matrix-spike results that are outside the acceptance limits, by allowing the analyst to differentiatebetween: 1)(1) spike-solution and spiking-technique problems, and 2.)(2) matrix interferences. Recommended spike levels arelist
29、ed in Annex, Table A1.3.3.2.12 stock-standard solution, na concentrated solution (containing one or more analytes), obtained as a certified solutionfrom a reputable source.3.2.13 surrogate spikes, nlanthanum and terbium are added at a concentration of 5 ng/mL(each) in the initial 100-mLsample.3.2.13
30、.1 DiscussionThe surrogate spikes are then preconcentrated to approximately 50 ng/mLin the final 10-mLsample without correcting for the finalpreconcentration. The surrogate spikes are used to determine potential method problems such as improper pH adjustment or faultyfilters used when collecting the
31、 precipitate.3.2.14 total recoverable, nthe concentration of analyte determined on a whole, unfiltered water or solid sample followingvigorous digestion as described in USU.S. EPA Method 1640.4. Summary of Practice4.1 In this practice, trace elements are separated from seawater matrix elements (in p
32、articular Na, Ca, and Mg) andpreconcentrated by a factor of 10 by reductive precipitation using sodium borohydride as a reducing agent.4.2 Iron (Fe) and palladium (Pd) are added to the samples to aid co-precipitation of metal borides and to enhance theprecipitation of metals in their elemental form.
33、4.3 For total metals, the whole sample is acidified at the time of collection with ultrapure nitric acid at an equivalentconcentration of 0.20 % to a pH 2.4.4 For dissolved metals, the sample is filtered through a 0.450.4 m filter at the time of collection then acidified with ultrapurenitric acid at
34、 an equivalent concentration of 0.20 % to a pH 2.NOTE 1It is important to minimize the amount of nitric acid used to preserve the samples. A pH adjustment to a pH between 8 and 10 usingammonium hydroxide is performed during the co-precipitation reaction and it is important to minimize the amount of
35、ammonium hydroxide required forthis adjustment to reduce potential contamination of the samples.4.5 The precipitate is collected by filtration through a 0.4 mmm filter and the salt matrix is eliminated with the filtrate. Thefilter and precipitate are digested with nitric acid and hydrogen peroxide f
36、or analysis by ICP-MS.5. Significance and Use5.1 Ambient marine waters generally contain very low concentrations of toxic metals that require sensitive analytical methods,such as ICP-MS, to detect and measure the metals concentrations.5.2 Due to the high dissolved salt concentrations present in seaw
37、ater, sample pretreatment is required to remove signalsuppression and significant polyatomic interferences due to the matrix both of which compromise detection limits.6. Interferences6.1 ContaminationConcentrations of trace metals in ambient marine waters may be very low and it is imperative that ex
38、tremecare be taken to avoid contamination when collecting, preparing and analyzing ambient water samples. U.S. EPA Method 1669details appropriate clean sampling protocols.6.2 Isobaric polyatomic ion interferences are caused by ions consisting of more than one atom which have the same nominalmass-to-
39、charge ratio as the isotope of interest, and which may not be resolved by the mass spectrometer in use. These ions arecommonly formed in the plasma or interface system from support gases or sample components. Most of the common interferenceshave been identified, and are listed in Test Method D5673.
40、Such interferences must be recognized, and when they cannot beavoided by the selection of alternative analytical isotopes, appropriate corrections must be made to the data. Equations for thecorrection of data should be established at the time of the analytical run sequence, as the polyatomic ion int
41、erferences will be highlydependent on the sample matrix and chosen instrument operating parameters. Major interfering ions from seawater matrixes areeliminated in this practice by the selective precipitation of metals.6.3 Palladium reagent in the analyzed samples interferes with both silver masses 1
42、07Ag and 109Ag due to the formation of thePdH+ ion.7. Hazards7.1 The toxicity or carcinogenicity of reagents used in this method has not been fully established. Each chemical should beregarded as a potential health hazard and exposure to these compounds should be as low as reasonably achievable.Aref
43、erence fileof materialsafety data handling sheets (MSDS)(SDS) for each chemical used in this procedure should be available to all personnelinvolved in the chemical analysis.D6800 1838. Sample Collection, Containers, Preservation, and Storage8.1 All samples must be collected using a sampling plan tha
44、t addresses the considerations discussed in U.S. EPAMethod 1669.Contamination control is critical at all steps of sample handling due to the low measurement limit goals of this method.8.2 Water samples must be acidified with an equivalent concentration of 0.2 % ultrapure nitric acid (that is, 1 mL H
45、NO3 to 500mL 500-mL sample). Samples are kept at room temperature in plastic bins. Use the minimum amount of acid necessary to reducethe sample pH 2. Excess acid will complicate the pH adjustment during the reductive precipitation reaction.8.3 Use only acid washed sample containers prepared as descr
46、ibed in USU.S. EPA Method 1669. High-density polyethylene(HDPE) is preferred.8.4 Sample Preservation:8.4.1 Total Recoverable MetalsFor determination of total recoverable elements in aqueous samples, preserve the wholesample by adding ultra pure nitric acid to pH 2 (normally 1 mL per 500 mL of sample
47、) at the time of collection or upon receiptwith an equivalent concentration of 0.2 % ultrapure nitric acid (that is, 1 mL HNO3 to 500 mL 500-mL sample).NOTE 2Samples that cannot be acid preserved at the time of collection because of sampling limitations or transport restrictions, should be acidified
48、with ultra pure acid to pH 2 upon receipt in the laboratory. These samples must be then held for 16 h prior to sample preparation.8.4.2 Dissolved MetalsFor the determination of dissolved elements, the samples are filtered through a 0.450.4 m membranefilter or equivalent. Acidify the filtrate with ul
49、tra pure nitric acid to pH 2 immediately following filtration.9. Apparatus and Equipment9.1 Laboratory EquipmentFor the determination of trace levels of elements, contamination and loss are of primaryconsideration. Potential contamination sources include improperly cleaned laboratory apparatus and general contamination withinthe laboratory environment from dust, etc. A clean laboratory work area, designated for trace element sample handling must beused. Sample containers can introduce positive and negative errors in the determination of tra
