1、Designation: D7168 111Standard Test Method for99Tc in Water by Solid Phase Extraction Disk1This standard is issued under the fixed designation D7168; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A numb
2、er in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1NOTEAdded research report footnote to Section 16 editorially in June 2013.1. Scope1.1 This test method describes a solid phase extraction(SPE) procedu
3、re to separate99Tc from environmental watersamples (that is, non-process and effluent waters).Technetium-99 beta activity is measured by liquid scintillationspectrometry.1.2 This test method is designed to measure99Tc in therange of approximately 0.037 Bq/L (1.0 pCi/L) or greater for aone litre samp
4、le.1.3 The values stated in SI units are to be regarded asstandard. Values given in parentheses are provided for infor-mation purposes only.1.4 This method has been used successfully with tap water.It is the users responsibility to ensure the validity of this testmethod for samples larger than 1 L a
5、nd for waters of untestedmatrices.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limita
6、tions prior to use. For specific hazardstatements, see Section 9.2. Referenced Documents2.1 ASTM Standards:2D1129 Terminology Relating to WaterD1193 Specification for Reagent WaterD2777 Practice for Determination of Precision and Bias ofApplicable Test Methods of Committee D19 on WaterD3370 Practice
7、s for Sampling Water from Closed ConduitsD4448 Guide for Sampling Ground-Water Monitoring WellsD5847 Practice for Writing Quality Control Specificationsfor Standard Test Methods for Water AnalysisD6001 Guide for Direct-Push Groundwater Sampling forEnvironmental Site CharacterizationD7282 Practice fo
8、r Set-up, Calibration, and Quality Controlof Instruments Used for Radioactivity Measurements3. Terminology3.1 DefinitionsFor definitions of terms used in this testmethod, refer to Terminology D1129.4. Summary of Test Method4.1 Ameasured aliquant of sample is transferred to a beaker.Hydrogen peroxide
9、 is added to facilitate the formation of theextractable pertechnetate ion. The sample may be heated tooxidize organics if such are suspected to be present. The entiresample is passed through a technetium-selective SPE disk ontowhich the pertechnetate is adsorbed. The disk is transferred toa liquid s
10、cintillation vial, cocktail added, and the contents wellmixed. The beta emission rate of the sample is determined byliquid scintillation spectrometry. Chemical yield correctionsare determined by the method of standard additions.4.2 Minor differences in processing between ExtractionChromatographic Re
11、sin Discs and PTFE Membrane Disks areaddressed in Variations A and B of the method.5. Significance and Use5.1 This method has not been evaluated for all possiblematrices. Method suitability should be determined on specificwaters of interest.6. Interferences6.1 Suspended materials must be removed by
12、filtration orcentrifuging prior to processing the sample. Suspended par-ticulate matter in the sample will be physically trapped in partor in whole on or in the SPE extraction material. This may leadto potential inclusion of radionuclide bearing solids or to signalquenching in the liquid scintillati
13、on measurement.6.2 Technetium-99 activity in the sample may overwhelmthe signal from the99Tc spike addition and interfere withaccurate determination of chemical yield. Samples for which1This test method is under the jurisdiction of ASTM Committee D19 on Waterand is the direct responsibility of Subco
14、mmittee D19.04 on Methods of Radiochemi-cal Analysis.Current edition approved May 15, 2011. Published July 2011. Originallypublished in 2005. Last previous edition published 2005 as D7168 051. DOI:10.1520/D7168-11E01.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact AST
15、M Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1the unspiked sample count rate
16、 exceeds 50 % of the spikedsample count rate should be reprepared with an appropriatelyadjusted aliquant and spike addition levels to minimize contri-butions to uncertainty in the determination of the chemicalyield.6.3 Organic compounds present in significant quantities inthe sample may degrade the
17、extraction performance of the SPEdisk or may lead to elevated levels of quench during liquidscintillation analysis. After the addition of hydrogen peroxide,the sample may be heated to destroy trace organic matter in thesample. If organic components are present in the sample whichmay survive the pero
18、xide digestion, these may be removedwith an appropriate organic removal resin or disk (such asAmberchrom resin or disk) prior to passing the sample throughthe extraction chromatographic resin disc.6.4 The disk may retain tritium-labeled compounds. Settingthe99Tc counting window above the maximum ene
19、rgy for thetritium beta particle will eliminate potential tritium interfer-ence.6.5 Elevated levels of nitrates ( 10 000 ppm) will interferewith uptake of99Tc.6.6 The higher energy region above the maximum energyfor99Tc should be monitored to help identify cases of signifi-cant actinide interference
20、.6.7 Elevated levels of radionuclides present in anionic formsuch as iodate, iron (III) and antimony may interfere withmeasurement of technetium and lead to a positive bias insample results. Significantly elevated levels of actinides(esp.234Th decay progeny of uranium) when present in thesample may
21、cause a high bias in the reported99Tc activity.Manufacturer specific recommendations about interferencesshould be taken into consideration when determining theapplicability of this method for a given matrix.7. Apparatus7.1 Filtering Apparatus, 47-mm diameter filter apparatus asrecommended by the SPE
22、 manufacturer.7.2 Liquid Scintillation Counter, with multiple energy re-gion of interest (ROI) capabilities.7.3 Scintillation Vials, 20-mL vials, low potassium glass orplastic, exhibiting suitable optical reproducibility so as not tocause erratic results between samples.8. Reagents and Materials8.1
23、Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents shall conform to the specifications of the Commit-tee on Analytical Reagents of the American Chemical Society,where such specifications are available. Other grades may beu
24、sed, provided that the reagent is of sufficiently high purity topermit its use without increasing the background of themeasurement. Some reagents, even those of high purity, maycontain naturally-occurring radioactivity, such as isotopes ofuranium, radium, actinium, thorium, rare earths and potassium
25、compounds and/or artificially produced radionuclides.Consequently, when such reagents are used in the analysis oflowradioactivity samples, the activity of the reagents shall bedetermined under analytical conditions that are identical tothose used for the sample. The activity contributed by thereagen
26、ts may be considered to be a component of backgroundand applied as a correction when calculating the test sampleresult. This increased background reduces the sensitivity of themeasurement.8.2 Purity of WaterUnless otherwise indicated, referencesto water shall be understood to mean reagent water conf
27、ormingto Specification D1193, Type III.8.3 Radioactive PurityRadioactive purity shall be suchthat the measured radioactivity of blank samples does notexceed the calculated probable error of the measurement.8.4 Technetium-Specific Solid Phase Extraction (SPE) Disksor Membranes (Extraction Chromatogra
28、phic Resin Discs3orPTFE Membrane Disks3,4).8.5 Hydrochloric Acid, 0.5MAdd 42 mL concentratedHCl to 400 mL of reagent water. Dilute to 1 L with water.8.6 Nitric Acid, concentrated.8.7 Hydrogen Peroxide, 30 %.8.8 Technetium-99 as pertechnetate in water or dilute basesolution, traceable to a national s
29、tandards body (such as NISTin the U.S.).8.9 Liquid Scintillation CocktailCommercially preparedLSC cocktail or equivalent.3,59. Hazards9.1 Use extreme caution when handling all acids. They areextremely corrosive, and skin contact could result in severeburns.9.2 When diluting concentrated acids, alway
30、s use safetyglasses and protective clothing, and add the acid to the water.10. Sampling10.1 Collect a sample in accordance with Practice D3370,D4448 or D6001.11. Preservation11.1 Preservation of samples being analyzed for99Tc is notrequired.11.1.1 Samples may be preserved by freezing. Allowsamples t
31、o come to ambient temperature prior to processing.11.1.2 Samples may be processed if they have been previ-ously preserved to pH less than 2 with nitric or hydrochloricacid. It is noted that high concentrations of nitric acid will3The sole source of supply of the Eichrom TEVA Discs known to thecommit
32、tee at this time is Eichrom Industries, Inc., Lisle, IL. If you are aware ofalternative suppliers, please provide this information to ASTM InternationalHeadquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee,1which you may attend.43M Empore T
33、c Rad Disks (3M, St. Paul, MN) have been found satisfactoryfor this purpose.5Ultima Gold LLT (Perkin Elmer Life and Analytical Sciences, 710 Bridge-port Avenue, Shelton, CT 06484-4794) has been found satisfactory for this purpose.D7168 1112adversely affect chemical yield.Although yield corrections w
34、illcorrect for losses, better results may be obtained by usingunpreserved samples.12. CalibrationNOTE 1See D7282 for additional details on set-up, calibration andquality control of liquid scintillation counters.12.1 The fractional detection efficiency (Tc) is determinedas outlined in subsequent step
35、s.12.1.1 Prepare triplicate working calibration source (WCS)adding at least 20 Bq (540 pCi) of traceable99Tc in thepertechnetate form to each of three 100 mL portions of reagentwater. Each of the three samples is processed using eithermethod variation (A or B), as appropriate.12.1.2 Collect the effl
36、uents from the three WCS. Process thecomposited solution according to the method to verify thatgreater than 99 % of the technetium was retained by the SPEmaterial in the calibration runs.12.1.2.1 If analysis of the combined effluent indicatesgreater than 1% breakthrough of Tc, the concentration of t
37、heWCS activity should be corrected for the losses. If thebreakthrough of99Tc is greater than 5%, the cause for thelosses should be identified and new WCS prepared.12.1.3 An analyte-free aliquant of 100 mL reagent water isalso processed as a background subtraction count (BSC).12.1.4 Count the three v
38、ials containing the WCS and theBSC in a liquid scintillation counter for a time sufficient toamass greater than 10 000 counts for each of the WCS.12.1.5 Calculate the99Tc Detection Efficiency (Tc) for eachof the three vials:Tc5Rg2 RcbAc(1)where:Rg= gross count rate of the vial in the99Tc count windo
39、win counts per second,Rcb= count rate of the BSC associated with the efficiencymeasurement in the99Tc count window in counts persecond, andAc= activity of standard99Tc added to each vial (Bq).12.2 Calculate the average, Tc, and the relative standarddeviation, sr(Tc), for the three efficiency values.
40、 The relativestandard deviation of these parameters is used to estimate therelative standard uncertainty of the average efficiency, ur(Tc),as follows:urHTc! 5 sr2Tc!31ur2Ac! (2)where:ur(Ac) = relative standard uncertainty of the activity ofstandard99Tc added to each vial.12.3 A background subtractio
41、n count (BSC) vial consistingof reagent water shall be processed and analyzed with eachbatch of samples to determine the background count rate incounts per second (Rb) to be used for the calculation of sampleresults.13. ProcedureNOTE 2To minimize the risk of cross-contamination while ensuringreprodu
42、cibility between the sample and its spiked duplicate, each aliquant-spiked aliquant pair should be run simultaneously and in parallel, usingseparate dedicated filtration apparatus.NOTE 3The sample aliquant is typically 1 L but depending on theactivity present and the required detection limit for the
43、 analysis, this mayvary from 0.1 to several litres.NOTE 4A background subtraction count (BSC) consisting of a vial,cocktail and blank disk is performed with each batch to determine thebackground count rate to be subtracted from each measurement (Rbin Eq3). If the BSC is to be reused, the user should
44、 determine its stability andshelf-life.13.1 Method Variation AFor use with Extraction Chro-matographic Resin Discs:13.1.1 For each sample and OC sample to be processed,transfer duplicate 1 L aliquants of sample to each of twobeakers.13.1.2 Acidify samples to pH 2 with nitric acid, if not donepreviou
45、sly.13.1.3 Add a known quantity (20 Bq) of a traceable99Tcsolution to the second aliquant of the sample which is labeledas the spiked sample. (See section 6.2 for comment onappropriate spiking level.)13.1.4 Add 10 mL of 30 % H2O2to each sample whilestirring.13.1.5 If the presence of organic interfer
46、ences is suspected,heat the sample on a hotplate at approximately 80C for about1 hour or until any visible reaction has subsided. Allow thesample to cool to ambient temperature before proceeding withsubsequent steps.13.1.6 Using forceps, carefully position a disc on the filterstand. Secure the funne
47、l reservoir over the disc.13.1.7 Precondition the disc by allowing 25 mL of water topass through the disc by gravity. Check the filter funnel forleaks.13.1.8 Add the sample to the funnel reservoir and allow topass through the disc by gravity flow (nominal flow rate shouldnot exceed 100 mL/min). If n
48、eeded vacuum may be used tomaintain adequate flow.13.1.9 Rinse the disc with 25 mL of 0.5M HCl.13.1.10 Rinse the disc with 100 mL of water.13.1.11 Apply vacuum to the filtration apparatus to removeresidual liquid from the disc.13.1.12 Detach the reservoir from the filter apparatus.13.1.13 Using forc
49、eps, remove and carefully roll the discand transfer to a scintillation vial.13.1.14 Add 15 mL of liquid scintillation cocktail.13.1.15 Cap and shake the contents of the vial, to allow thedisc to disintegrate. A vortex mixer may be used.13.1.16 Count the sample test source (STS) in a liquidscintillation counter using an optimized energy window withinthe range of 20 to 292 keV for a period of time adequate toachieve the required detection limit.13.2 Method Variation BFor use with PTFE ExtractionMembranes:13.2.1 For each sample and QC sample to be
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