1、Designation: D4785 08 (Reapproved 2013)1Standard Test Method forLow-Level Analysis of Iodine Radioisotopes in Water1This standard is issued under the fixed designation D4785; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year
2、 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.1NOTEWarning notes were editorially updated throughout in June 2013.1. Scope1.1 This test method covers the quantification of
3、low levelsof radioactive iodine in water by means of chemical separationand counting with a high-resolution gamma ray detector.Iodine is chemically separated from a 4-L water sample usingion exchange and solvent extraction and is then precipitated ascuprous iodide for counting.1.2 The values stated
4、in SI units are to be regarded asstandard. The values given in parentheses are provided forinformation purposes only.1.3 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-priat
5、e safety and health practices and determine the applica-bility of regulatory limitations prior to use. For specific hazardstatements, see 8.17, 8.18, 8.19, Section 9, and 13.2.11.2. Referenced Documents2.1 ASTM Standards:2D1129 Terminology Relating to WaterD1193 Specification for Reagent WaterD2777
6、Practice for Determination of Precision and Bias ofApplicable Test Methods of Committee D19 on WaterD3370 Practices for Sampling Water from Closed ConduitsD3648 Practices for the Measurement of RadioactivityD3649 Practice for High-Resolution Gamma-Ray Spectrom-etry of WaterD5847 Practice for Writing
7、 Quality Control Specificationsfor Standard Test Methods for Water AnalysisD3856 Guide for Management Systems in LaboratoriesEngaged in Analysis of Water3. Terminology3.1 DefinitionsFor definitions of terms used in this testmethod, refer to Terminology D1129.4. Summary of Test Method4.1 Sodium iodid
8、e is added as a carrier prior to performingany chemical separations. The samples undergo an oxidation-reduction process to ensure exchange between the carrier andthe radioactive iodide. Hydroxylamine hydrochloride and so-dium bisulfite are added to convert all the iodine to iodidewhich is then remov
9、ed by anion exchange. Subsequent elutionof the iodide is followed by oxidation-reduction to elementaliodine. The elemental iodine is purified by solvent extraction,reduced to iodide, and precipitated as cuprous iodide. Thechemical recovery is determined from the recovery of theiodide carrier.5. Sign
10、ificance and Use5.1 This test method was developed for measuring lowlevels of radioactive iodine in water. The results of the test maybe used to determine if the concentration of several radioiso-topes of iodine in the sample exceeds the regulatory statutes fordrinking water. With a suitable countin
11、g technique, samplesize, and counting time, a detection limit of less than 0.037Bq/L (1 pCi/L) is attainable by gamma-ray spectroscopy. Thismethod was tested for131I . Other iodine radioisotopes shouldbehave in an identical manner in this procedure. However,other iodine radioisotopes have not been t
12、ested according toPractice D2777. The user of this method is responsible fordetermining applicability, bias, and precision for the measure-ment of other iodine radioisotopes using this method.5.2 This procedure addresses the analysis of iodine radio-isotopes with half-lives greater than 2 hours, whi
13、ch include121I,123I,124I,125I,126I,129I,130I,131I,132I,133I, and135I.6. Interferences6.1 Stable iodine in the sample will interfere with thechemical recovery determination. One milligram of ambientiodine would produce a bias of about 4 %.1This test method is under the jurisdiction of ASTM Committee
14、D19 on Waterand is the direct responsibility of Subcommittee D19.04 on Methods of Radiochemi-cal Analysis.Current edition approved June 15, 2013. Published July 2013. Originallyapproved in 1988. Last previous edition approved in 2008 as D4785 08. DOI:10.1520/D4785-08R13.2For referenced ASTM standard
15、s, visit the ASTM website, www.astm.org, orcontact ASTM 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 19
16、428-2959. United States16.2 There are numerous characteristic iodine X-rays at andbelow 33.6 keV which are indicative of iodine, but not aspecific radioisotope of iodine. It is recommended that onlydiscreet gamma energy lines at and above 35.5 keV be used foridentification and quantification of iodi
17、ne radioisotopes.7. Apparatus7.1 Analytical Balance, readable to 0.1 mg.7.2 Flexible Polyvinyl Chloride (PVC) Tubing, 6.35 mm (14in.) outside diameter, 1-m length.7.3 Gamma-Ray Spectrometry SystemHigh resolutiongamma spectrometer (high purity germanium or equivalent)with a useful energy range of app
18、roximately 30 keV to 1800keV (see Practice D3649).7.4 Glass Fiber Filter Paper, 11.5-cm diameter.7.5 Ion Exchange Column, glass tube, 35 6 2-mm insidediameter, 150-mm length, fitted with No. 8 one-hole rubberstoppers and perforated disk.7.6 Membrane Filters, 0.4 or 0.45-m pore size, 25-mmdiameter, w
19、ith suitable filter holder and vacuum filter flask.7.7 Peristaltic Tubing Pump, variable speed, fitted withvinyl or silicone tubing.7.8 pH Meter.7.9 Sintered Glass Filter, Bchner funnel, 150-mL size,medium or coarse porosity with suitable one-hole stopper andvacuum filter flask.7.10 Vacuum Desiccato
20、r.7.11 Vortex Mixer.8. Reagents and Materials8.1 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 onAnalytical Reagents of theAmerican Chemical Society.3Other grades
21、may be used provided they are of sufficiently highpurity to permit their use without reducing the accuracy of thedetermination.8.2 Purity of WaterUnless otherwise indicated, referenceto water shall be understood to mean reagent water conformingto Specification D1193, Type III.8.3 Radioactive PurityR
22、adioactive purity shall be suchthat the measured radioactivity of blank samples does notexceed the calculated probable error of the measurement.8.4 Ammonium Hydroxide (sp gr 0.90)Concentrated am-monium hydroxide (NH4OH).8.5 Ammonium Hydroxide (1.4 M)Mix one volume ofconcentrated NH4OH (sp gr 0.90) w
23、ith nine volumes of water.8.6 Anion Exchange ResinStrongly basic, styrene, quar-ternary ammonium salt, 2050 mesh, chloride form, Dowex1-X8, or equivalent.8.7 Cuprous Chloride Solution (approximately 10 mg CuCl/mL)Dissolve 10 g of CuCl (99.99 %) in 26 mL of concen-trated HCl (sp gr 1.19). Add this so
24、lution to 1000 mL of NaClsolution (1 M) slowly with continuous stirring. Add a smallquantity of metallic copper (for example, 5 to 10 copper metalshot) to the solution for stabilization.4Store the CuCl in adesiccator.8.8 Hydrochloric Acid (sp gr 1.19)Concentrated hydro-chloric acid (HCl).8.9 Hydroch
25、loric Acid Solution (0.3 M)Dilute 25 mL ofconcentrated HCl to 1000 mL with water.8.10 Hydroxylamine Hydrochloride (NH2OH:HCl)Crystals.8.11 Iodide Carrier Solution (25 mg I/mL)Dissolve 14.76g of NaI in approximately 80 mL of water in a 500-mLvolumetric flask and dilute to volume. Standardize using th
26、eprocedure in Section 10.8.12 Iodine-131 Standardizing SolutionNational stan-dardizing body such as National Institute of Standards andTechnology (NIST), traceable solution with a typical concen-tration range from 1 to 10 kBq/mL.8.13 Nitric Acid (sp gr 1.42)Concentrated HNO3.8.14 Nitric Acid (1.4 M)
27、Mix 1 volume of concentratedHNO3(sp gr 1.42) with 10 volumes of water.8.15 Sodium Bisulfite Solution, (2 M)Dissolve 104.06 g ofNaHSO3in approximately 300 mL of water in a 500-mLvolumetric flask and dilute to volume.8.16 Sodium Chloride Solution (1 M)Dissolve 58.45 g ofNaCl in approximately 500 mL of
28、 water in a 1000 mLvolumetric flask and dilute to volume.8.17 Sodium Hydroxide Solution (12.5 M)Dissolve 500 gof NaOH in 800 mL of water and dilute to 1 L. (WarningThe dissolution of sodium hydroxide may produce excessiveheat.)8.18 Sodium Hypochlorite (NaOCl)Approximately 5 to6 %. Commercially avail
29、able bleach is acceptable.(WarningAcidification of NaOCl produces toxic chlorinegas and must be handled in a fume hood.)8.19 Toluene. (WarningToluene is a carcinogen and mustbe handled and disposed of in an approved manner.)8.20 Calibration Standard(s)Known amounts of125I,129I,and131I are used for c
30、alibration when determining theseradionuclides. A mixed-gamma standard, for example,241Am,109Cd,57Co,141Ce,113Sn,137Cs,88Y, and60Co, is used forcalibration over an extended energy range as required for the3Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washing
31、ton, DC. For Suggestions on the testing of reagents notlisted by the American Chemical Society, see Annual Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.4CuCl soluti
32、on is not stable. It can be oxidized to the Cu+2state by air after aperiod of time, when the solution will turn dark green. If this happens, prepare afresh solution. The shelf life of the solution can be extended by displacing the airover the remaining solution with nitrogen or argon gas after each
33、use and thenclosing the container promptly.D4785 08 (2013)12determination of additional radioisotopes of iodine. Thesestandards should be mounted on the filter as described in 7.6.The known amounts of the radionuclides must be traceable toa national standardizing body such as NIST in the USA. Thesta
34、ndard may be prepared by the laboratory performing thismethod or by a commercial supplier of such standards.Alternate radionuclides may be used for calibration providedthat they have gamma ray energies covering the range ofinterest for the iodine radionuclides to be analyzed.9. Hazards9.1 Due to the
35、 potential health effects from handling thesecompounds, the steps utilizing NaOCl and toluene must becarried out in a fume hood. Toluene is a carcinogen andacidification of NaOCl liberates toxic Cl2gas.10. Standardization of Iodide Carrier10.1 Pipet 1.0 mL of iodide carrier reagent into each of five
36、100-mL centrifuge tubes containing 50 mL of deionized water.10.2 Add 0.1 mL of 2 M NaHSO3to each solution and stirvigorously using a vortex mixer. Add 5.0 mL of freshlyprepared CuCl solution.10.3 Using a pH meter, check the pH of each solution andadjust the pH to between 2.40 to 2.50 with 0.3 M HCl
37、or 1.4 MNH4OH.10.4 Place each solution in a warm (approximately 50 to60C) water bath for 5 to 10 min, stirring occasionally.10.5 Rinse each CuI precipitate onto a separate preweighed0.45-m membrane filter mounted in a vacuum filtrationassembly. Rinse the walls of the filter holder with approxi-matel
38、y 50 mL of water.10.6 Dry all samples in a vacuum desiccator for a minimumof 60 min or to constant weight. Remove and weigh the filterand precipitate. Record all data.10.7 Determine the net weight of each CuI precipitate.10.8 Use the mean of the five weights for the standardweight. The relative stan
39、dard deviation of the mean should notexceed 0.025.11. Calibration of High-Resolution Gamma-RaySpectroscopy System11.1 Accumulate an energy spectrum using the calibrationstandard (8.20) traceable to a national standards body, in thegeometrical position representing that of the samples to beanalyzed.
40、Accumulate sufficient net counts (total counts minusthe Compton baseline) in each full-energy gamma-ray peak ofinterest to obtain a relative standard counting uncertainty of1%.11.2 Using the gamma-ray emission data from the calibra-tion standard and the peak location data from the calibrationspectru
41、m, establish the energy per channel relationship (energycalibration) as:En 5 Offset1Ch 3Slope! (1)where:En = peak energy (keV),Offset = energy offset for the energy calibration equation(keV),Ch = peak location channel number, andSlope = energy calibration equation slope (keV per chan-nel).NOTE 1Most
42、 modern spectroscopy software packages perform thiscalculation, and may include higher-order polynomial terms to account forminor non-linearity in the energy calibration.11.3 Using the gamma emission data from the calibrationstandard and the peak resolution data from the calibrationspectrum, establi
43、sh the resolution versus energy relationship(energy calibration) as:FWHM 5 Offset1Ch 3Slope! (2)where:FWHM = full width of the peak at one-half the maximumcounts in the centroid channel (keV),Offset = width offset for the resolution calibration equation(keV),En = peak energy (keV), andSlope = resolu
44、tion calibration equation slope (keV/keV).NOTE 2Most modern spectroscopy software packages perform thiscalculation, and may include higher-order polynomial terms to account fornon-linearity in the resolution calibration.11.4 For each gamma-ray photopeak, calculate the full-energy peak efficiency, f,
45、 as follows:f5RnR3DF(3)where:f= full-energy peak efficiency (counts per gamma rayemitted),Rn= net gamma-ray count rate in the full-energy peak ofinterest, counts per second (s1),R= gamma-ray emission rate, in gamma-rays per second(s1), as of the reference date and time of thecalibration standard,DF
46、= decay factor for the calibrating radionuclide, e(t1t0), = (ln 2) / t1/2,t1/2= half-life of calibrating radionuclide (half-life unitmust match that used for the time difference, t1t0),t0= reference date and time of the calibration standard,andt1= midpoint of sample count (date and time).11.5 Many m
47、odern spectrometry systems are computerizedand the determination of the gamma-ray detection efficienciesis performed automatically at the end of an appropriatecounting interval. Refer to the manufacturer instructions forspecific requirements and capabilities.11.6 Plot the values for the full-energy
48、peak efficiency (asdetermined in Section 11.5) versus gamma-ray energy. Com-pare the efficiency curve to the typical efficiency curve for thedetector type. The curve should be smooth, continuous andhave a shape similar to the detector being used. The plot willallow the determination of efficiencies
49、at energies throughoutthe range of the calibration energies and will show that thealgorithms used in computerized systems are providing validefficiency calibrations. Select the fit that has the best 95 %confidence limit around the fitted curve, has all data pointsD4785 08 (2013)13within 68 % of the value of the fitted curve, or both. This isaccomplished by calculating the bias between the actualefficiency and the efficiency calculated with the fitted curve.11.7 Save or store the values of energy versus efficiency forfuture refer
