1、Designation: D7168 111D7168 16Standard 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
2、. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1 NOTEAdded research report footnote to Section 16 editorially in June 2013.1. Scope1.1 This test method describes a solid phase extraction (SP
3、E) procedure to separate 99Tc from environmental water samples (thatis, non-process and effluent waters). (non-process-related or effluent water samples). Technetium-99 beta activity is measured byliquid scintillation spectrometry.1.2 This test method is designed to measure 99Tc in the range of appr
4、oximately 0.037 Bq/L (1.0 pCi/L) or greater for a one litresample.1.3 The values stated in SI units are to be regarded as standard. Values given in parentheses are provided for informationpurposes only.1.3 This test method has been used successfully with tap water. It is the usersusers responsibilit
5、y to ensure the validity of thistest method for samples larger than 1 L and for waters of untested matrices.1.4 Technetium-99 alternatively can be determined in water samples using Practice D8026.1.5 The values stated in SI units are to be regarded as standard. The values given in parentheses are pr
6、ovided for informationonly and are not considered standard.1.6 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 and health practices and determine the applicabil
7、ity of regulatorylimitations prior to use. For specific hazard statements, 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 of Applicable Test Methods of Committee D
8、19 on WaterD3370 Practices for Sampling Water from Closed ConduitsD4448 Guide for Sampling Ground-Water Monitoring WellsD5847 Practice for Writing Quality Control Specifications for Standard Test Methods for Water AnalysisD6001 Guide for Direct-Push Groundwater Sampling for Environmental Site Charac
9、terizationD7282 Practice for Set-up, Calibration, and Quality Control of Instruments Used for Radioactivity MeasurementsD7902 Terminology for Radiochemical AnalysesD8026 Practice for Determination of Tc-99 in Water by Inductively Coupled Plasma Mass Spectrometry (ICP-MS)3. Terminology3.1 Definitions
10、Definitions: For definitions of terms used in this test method, refer to Terminology D1129.3.1.1 For definitions of terms used in this standard, refer to Terminologies D7902 and D1129.1 This test method is under the jurisdiction of ASTM Committee D19 on Water and is the direct responsibility of Subc
11、ommittee D19.04 on Methods of RadiochemicalAnalysis.Current edition approved May 15, 2011Nov. 1, 2016. Published July 2011November 2016. Originally published in 2005. Last previous edition published 20052011 asD7168 05111. DOI: 10.1520/D7168-11E01.10.1520/D7168-16.2 For referencedASTM standards, vis
12、it theASTM website, www.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.This document is not an ASTM standard and is intended only to provide the user of an ASTM standa
13、rd 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 published by ASTM
14、is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States14. Summary of Test Method4.1 A measured aliquant of sample is transferred to a beaker. Hydrogen peroxide is added to facilitate the formation of
15、 theextractable pertechnetate ion. The sample may be heated to oxidize organics if such are suspected to be present. The entire sampleis passed through a technetium-selective SPE disk onto which the pertechnetate is adsorbed. The disk is transferred to a liquidscintillation vial, cocktail added, and
16、 the contents well mixed. The beta emission rate of the sample is determined by liquidscintillation spectrometry. Chemical yield corrections are determined by the method of standard additions.4.2 Minor differences in processing between Extraction Chromatographic Resin Discs and PTFE Membrane Disks a
17、readdressed in Variations A and B of the test method.5. Significance and Use5.1 This test method has not been evaluated for all possible matrices. Method Test method suitability should be determined onspecific waters of interest.6. Interferences6.1 Suspended materials must be removed by filtration o
18、r centrifuging prior to processing the sample. Suspended particulatematter in the sample will be physically trapped, in part or in whole, on or in the SPE extraction material. This may lead to potentialinclusion of radionuclide bearing solids or to signal quenching in the liquid scintillation measur
19、ement.6.2 Technetium-99 activity in the sample may overwhelm the signal from the 99Tc spike addition and interfere with accuratedetermination of chemical yield. Samples for which the unspiked sample count rate exceeds 50 % of the spiked sample count rateshould be reprepared with an appropriately adj
20、usted aliquant and spike addition levels to minimize contributions to uncertainty inthe determination of the chemical yield.6.3 Organic compounds present in significant quantities in the sample may degrade the extraction performance of the SPE diskor may lead to elevated levels of quench during liqu
21、id scintillation analysis. After the addition of hydrogen peroxide, the samplemay be heated to destroy trace organic matter in the sample. If organic components are present in the sample which may survivethe peroxide digestion, these may be removed with an appropriate organic removal resin or disk (
22、such as Amberchrom3 resin ordisk) prior to passing the sample through the extraction chromatographic resin disc.6.4 The disk may retain tritium-labeled compounds. Setting the 99Tc counting window above the maximum energy for thetritium beta particle will eliminate potential tritium interference.6.5
23、Elevated levels of nitrates ( 10 000 ppm)(10 000 mg L1) will interfere with uptake of 99Tc.6.6 The higher energy region above the maximum energy for 99Tc should be monitored to help identify cases of significantactinide interference.6.7 Elevated levels of radionuclides present in anionic form such a
24、s iodate, iron (III) and antimony may interfere withmeasurement of technetium and lead to a positive bias in sample results. Significantly elevated levels of actinides (esp. 234Th decayprogeny of uranium) when present in the sample may cause a high bias in the reported 99Tc activity. Manufacturer sp
25、ecificrecommendations about interferences should be taken into consideration when determining the applicability of this test method fora given matrix.7. Apparatus7.1 Filtering Apparatus, 47-mm diameter filter apparatus as recommended by the SPE manufacturer.7.2 Liquid Scintillation Counter,Spectrome
26、ter, with multiple energy region of interest (ROI) capabilities.7.3 Scintillation Vials, 20-mL vials, low potassium glass or plastic, exhibiting suitable optical reproducibility so as not to causeerratic results between samples.8. Reagents and Materials8.1 Purity of ReagentsReagent grade chemicals s
27、hall be used in all tests. Unless otherwise indicated, it is intended that allreagents shall conform to the specifications of the Committee on Analytical Reagents of the American Chemical Society, wheresuch specifications are available. Other grades may be used, provided that the reagent is of suffi
28、ciently high purity to permit itsuse without increasing the background of the measurement. Some reagents, even those of high purity, may containnaturally-occurring radioactivity, such as isotopes of uranium, radium, actinium, thorium, rare earths and potassium compoundsand/orcompounds, or artificial
29、ly produced radionuclides. radionuclides, or combination thereof. Consequently, when such reagentsare used in the analysis of lowradioactivity low radioactivity samples, the activity of the reagents shall be determined under3 Amberchrom is a trademark of the Dow Chemical Company, Midland, MI.D7168 1
30、62analytical conditions that are identical to those used for the sample. The activity contributed by the reagents may be consideredto be a component of background and applied as a correction when calculating the test sample result. This increased backgroundreduces the sensitivity of the measurement.
31、8.2 Purity of WaterUnless otherwise indicated, references to water shall be understood to mean reagent water conforming toSpecification D1193, Type III.8.3 Radioactive PurityRadioactive purity shall be such that the measured radioactivity of blank samples does not exceed thecalculated probable error
32、 of the measurement.8.4 Technetium-Specific Solid Phase Extraction (SPE) Disks or Membranes Membranes(Extraction Chromatographic ResinDiscs4 or PTFE Membrane Disks4, 5).8.5 Hydrochloric Acid, 0.5MAdd 42 mL concentrated HCl to 400 mL of reagent water. Dilute to 1 L with water.8.6 Nitric Acid, concent
33、rated.8.7 Hydrogen Peroxide, 30 %.8.8 Technetium-99 Technetium-99as pertechnetate in water or dilute base solution, traceable to a national standards body(such as NIST in the U.S.).8.9 Liquid Scintillation CocktailCommercially prepared LSC cocktail or equivalent.4, 69. Hazards9.1 Use extreme caution
34、 when handling all acids. They are extremely corrosive, and skin contact could result in severe burns.9.2 When diluting concentrated acids, always use safety glasses and protective clothing, and add the acid to the water.10. Sampling10.1 Collect a sample in accordance with PracticePractices D3370, o
35、r Guides D4448 or D6001.11. Preservation11.1 Preservation of samples being analyzed for 99Tc is not required.11.1.1 Samples may be preserved by freezing. Allow samples to come to ambient temperature prior to processing.11.1.2 Samples may be processed if they have been previously preserved to pH less
36、 than 2 with nitric or hydrochloric acid. Itis noted that high concentrations of nitric acid will adversely affect chemical yield. Although yield corrections will correct forlosses, better results may be obtained by using unpreserved samples.12. CalibrationNOTE 1See Practice D7282 for additional det
37、ails on set-up, calibration and quality control of liquid scintillation counters.12.1 The fractional detection efficiency (Tc) is determined as outlined in subsequent steps.12.1.1 Prepare triplicate working calibration source (WCS) adding at least 20 Bq (540 pCi) of traceable 99Tc in thepertechnetat
38、e form to each of three 100 mL portions of reagent water. Each of the three samples is processed using either testmethod variation (A or B), as appropriate.12.1.2 Collect the effluents from the three WCS. Process the composited solution according to the test method to verify thatgreater than 99 % of
39、 the technetium was retained by the SPE material in the calibration runs.12.1.2.1 If analysis of the combined effluent indicates greater than 1% breakthrough ofTc, the concentration of theWCS activityshould be corrected for the losses. If the breakthrough of 99Tc is greater than 5%, the cause for th
40、e losses should be identified andnew WCS prepared.12.1.3 An analyte-free aliquant of 100 mL reagent water is also processed as a background subtraction count (BSC).12.1.4 Count the three vials containing the WCS and the BSC in a liquid scintillation counterspectrometer for a time sufficientto amass
41、greater than 10 000 counts for each of the WCS.12.1.5 Calculate the 99Tc Detection Efficiency (Tc) for each of the three vials:Tc5Rg 2RcbAc(1)4 The sole source of supply of the Eichrom TEVA TEVA (a trademark of Eichrom Industries) Discs known to the committee at this time is Eichrom Industries, Inc.
42、,Lisle, IL. If you are aware of alternative suppliers, please provide this information to ASTM International Headquarters. Your comments will receive careful considerationat a meeting of the responsible technical committee,1 which you may attend.5 3M Empore Tc Rad Disks (3M, Empore (a trademark of 3
43、M Company, St. Paul, MN) Tc Rad Disks have been found satisfactory for this purpose.6 Ultima Gold LLT (Perkin Gold (a trademark of Perkin Elmer Life and Analytical Sciences, 710 Bridgeport Avenue, Shelton, CT 06484-4794)Shelton, CT) LLT hasbeen found satisfactory for this purpose.D7168 163where:Rg =
44、 gross count rate of the vial in the 99Tc count window in counts per second,Rcb = count rate of the BSC associated with the efficiency measurement in the 99Tc count window in counts per second, andAc = activity of standard 99Tc added to each vial (Bq).12.2 Calculate the average, Tc, and the relative
45、 standard deviation, sr(Tc), for the three efficiency values. The relative standarddeviation of these parameters is used to estimate the relative standard uncertainty of the average efficiency, ur(Tc), as follows:ur HTc!5sr2 Tc!3 1ur2 Ac! (2)where:ur(Ac) = relative standard uncertainty of the activi
46、ty of standard 99Tc added to each vial.12.3 A background subtraction count (BSC) vial consisting of reagent water shall be processed and analyzed with each batchof samples to determine the background count rate in counts per second (Rb) to be used for the calculation of sample results.13. ProcedureN
47、OTE 2To minimize the risk of cross-contamination while ensuring reproducibility between the sample and its spiked duplicate, each aliquant-spikedaliquant pair should be run simultaneously and in parallel, using separate dedicated filtration apparatus.NOTE 3The sample aliquant is typically 1 Lbut dep
48、ending on the activity present and the required detection limit for the analysis, this may vary from0.1 to several litres.NOTE 4Abackground subtraction count (BSC) consisting of a vial, cocktail and blank disk is performed with each batch to determine the backgroundcount rate to be subtracted from e
49、ach measurement (Rb in Eq 3). If the BSC is to be reused, the user should determine its stability and shelf-life.13.1 Test Method Variation AFor use with Extraction Chromatographic Resin Discs:13.1.1 For each sample and OC sample to be processed, transfer duplicate 1 L aliquants of sample to each of two beakers.13.1.2 Acidify samples to pH 2 with nitric acid, if not done previously.13.1.3 Add a known quantity (20 Bq) of a traceable 99Tc solution to the second aliquant of the sample which is labeled asthe spiked sample. (See section 6.2 for
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