1、Designation: D 4785 00aStandard Test Method forLow-Level Iodine-131 in Water1This standard is issued under the fixed designation D 4785; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parenth
2、eses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the quantification of low levelsof iodine-131 in water by means of chemical separation andcounting with a high-resolution gamma
3、 ray detector. Iodine ischemically separated from a 4-L water sample using ionexchange and solvent extraction and is then precipitated ascuprous iodide for counting.1.2 The values stated in SI units are to be regarded asstandard. The values given in parentheses are provided forinformation purposes o
4、nly.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-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. For specif
5、ic hazardstatements, see Note 2, Note 3, Note 8, and Section 9.2. Referenced Documents2.1 ASTM Standards:D 1129 Terminology Relating to Water2D 1193 Specification for Reagent Water2D 2777 Practice for Determination of Precision and Bias ofApplicable Test Methods of Committee D-19 on Water2D 3370 Pra
6、ctices for Sampling Water from Closed Con-duits2D 3648 Practices for Measurement of Radioactivity3D 3649 Practice for High-Resolution Gamma-Ray Spec-trometry of Water33. Terminology3.1 DefinitionsFor definitions of terms used in this testmethod, refer to Terminology D 1129.4. Summary of Test Method4
7、.1 Sodium iodide 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 iodidewhic
8、h is then removed by anion exchange. Subsequent elutionof the iodide followed by oxidation-reduction yields elementaliodine. The elemental iodine is purified by solvent extraction,reduced to iodide, and precipitated as cuprous iodide. Thechemical yield is determined from the recovery of the iodideca
9、rrier.5. Significance and Use5.1 This test method was developed for measuring lowlevels of iodine-131 in water. The results of the test may beused to determine if the concentration of iodine-131 in thesample exceeds the regulatory statutes for drinking water. Witha suitable counting technique, sampl
10、e size, and counting time,a detection limit of less than 0.037 Bq/L (1 pCi/L) is attainableby gamma-ray spectroscopy.6. Interferences6.1 Stable iodine in the sample will interfere with thechemical yield determination. One milligram of iodine wouldproduce a bias of about 4 %.7. Apparatus7.1 Analytica
11、l 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 resolution us-ing a high-purity germanium or lithium-drifted germaniumdetector (see Practice D 3649).7.4 Glass Fiber Filter Paper, 11.5-cm di
12、ameter.7.5 Ion Exchange Column, glass tube, 35 6 2-mm insidediameter, 150-mm length, fitted with No. 8 one-hole stoppersand perforated disk.7.6 Membrane Filters, 0.4 or 0.45-m pore size, 25-mmdiameter, with suitable filter holder and vacuum filter flask.7.7 Peristaltic Tubing Pump, variable speed, f
13、itted withvinyl or silicone tubing.7.8 pH Meter.7.9 Sintered Glass Filter, Buchner funnel, 150-mL size,medium or coarse porosity with suitable one-hole stopper andvacuum filter flask.7.10 Vacuum Desiccator.1This test method is under the jurisdiction of ASTM Committee D19 on Waterand is the direct re
14、sponsibility of Subcommittee D19.04 on Methods of Radiochemi-cal Analysis.Current edition approved July 10, 2000. Published October 2000. Originallypublished as D 4785 88. Last previous edition D 4785 00.2Annual Book of ASTM Standards, Vol 11.01.3Annual Book of ASTM Standards, Vol 11.02.1Copyright A
15、STM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.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
16、specifications of the Commit-tee onAnalytical Reagents of theAmerican Chemical Society.4Other grades may be used provided they are of sufficiently highpurity to permit their use without reducing the accuracy of thedetermination.8.2 Purity of Water Unless otherwise indicated, referenceto water shall
17、be understood to mean reagent water conformingto Specification D 1193, 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 Ammonium Hydroxide (sp gr 0.90)Concentrated am-mo
18、nium hydroxide (NH4OH).8.5 Ammonium Hydroxide (1.4 M)Mix one volume ofconcentrated NH4OH (sp gr 0.90) with 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 (approximatel
19、y 10 mg CuCl/mL)Dissolve 10 g of CuCl (99.99 %) in 26 mL of concen-trated HCl (sp gr 1.19). Add this solution 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.5Store the
20、CuCl in adesiccator.8.8 Hydrochloric Acid (sp gr 1.19)Concentrated hydro-chloric acid (HCl).8.9 Hydrochloric 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
21、 in approximately 80 mL of water in a 500-mLvolumetric flask and dilute to volume. Standardize using theprocedure in Section 10.8.12 Iodine-131 Standardizing SolutionNational Instituteof Standards and Technology (NIST), traceable solution with atypical concentration range from 1 to 10 kBq/mL.8.13 Ni
22、tric Acid (sp gr 1.42)Concentrated HNO3.8.14 Nitric Acid (1.4 M)Mix 1 volume of HNO3(sp gr1.42) with 10 volumes of water.8.15 Sodium Bisulfite Solution (2 M)Dissolve 104.06 gof NaHSO3in approximately 300 mL of water in a 500-mLvolumetric flask and dilute to volume.8.16 Sodium Chloride Solution (1 M)
23、Dissolve 58.45 g ofNaCl in approximately 500 mL of 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.NOTE 1Caution: The dissolution of sodium hydroxide may produceexcessive heat.8.18 Sodium Hypoch
24、lorite (NaOCl)Approximately 5 to6 %. Commercially available bleach is acceptable.NOTE 2Warning: Acidification of NaOCl produces toxic chlorinegas and must be handled in a fume hood.8.19 Toluene.NOTE 3Warning: Toluene is a carcinogen and must be handled anddisposed of in an approved manner.9. Hazards
25、9.1 Due to the 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 int
26、o each of five100-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 w
27、ith 0.3 M HCl 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
28、approxi-mately 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
29、relative standard deviation of the mean should notexceed 0.025.11. Calibration of High-resolution Gamma-raySpectroscopy System11.1 Prepare a set of three calibration sources in accordancewith the following:11.1.1 Add 50 mL of reagent water to a 150-mL beaker.11.1.2 Quantitatively add approximately 3
30、.7 kBq of NIST-traceable iodine-131 solution and swirl gently to mix.11.1.3 Follow 13.3.1-13.3.6.11.1.4 Count the calibration sources individually and accu-mulate 20 thousand to 50 thousand counts in the 365.48-kVphotopeak.4Reagent Chemicals, American Chemical Society Specifications, AmericanChemica
31、l Society, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, see Analar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockvil
32、le,MD.5CuCl solution 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 arg
33、on gas after each use and thenclosing the container promptly.D 4785 00a211.1.5 The absolute detection efficiency, E for the 364.5 keVgamma-ray, based on one calibration source is calculated asfollows:E 5 Cr/ AC*I! (1)where:Cr= the net count rate for the 364.5 keVgamma-ray line ofone of the reference
34、 iodine-131 sources in the samechemical form and geometerical arrangement as thesample,Ac= the activity in becquerels of that calibration source atthe midpoint of the counting period,I = the intensity for the 364.8 keV gamma-ray line,0.812.6Use the mean of three results. The relative standard devia-
35、tion of the mean should not exceed 5.0 %.12. Sampling12.1 Collect a sample in accordance with Practice D 3370.13. Procedure13.1 Sample Preparation:13.1.1 Measure or weigh 4 L of the sample into a suitableplastic container. While stirring, add 1.0 mL of iodide carrierand 5.0 mL of 5 to 6 % NaOCl. Sti
36、r approximately 3 to 5 min.13.1.2 Add 2.0 g of NH2OH:HCl, stir, and add 5.0 mL of 2M NaHSO3.Adjust the pH to 6.5 using 12.5 M NaOH or 1.4 MHNO3. Stir for 30 min.13.1.3 Filter the sample through a glass fiber filter anddiscard the residue.13.2 Anion Exchange Separation:13.2.1 Slurry 100 mL (wet volum
37、e) of washed anion ex-change resin into a 35-mm inside diameter glass column fittedat the lower end with a one-hole rubber stopper, perforateddisk, and a short length of 5-mm glass tubing connecting to theinlet side of the peristaltic pump (see Fig. 1).NOTE 4The resin should be washed with water unt
38、il the wash watershows no change in pH. This is most conveniently done by batchsequential washing of a relatively large quantity of resin and storing thewashed resin as a slurry.13.2.2 Leave approximately 25 mL of water on top of theresin bed and insert a glass wool plug, being careful not totouch t
39、he resin. Place a one-hole rubber stopper, fitted with ashort length of 5-mm glass tubing, in the top of the column andconnect it to a 1-m length of flexible PVC tubing.NOTE 5If a peristaltic pump is not available, the sample can be passedthrough the column by gravity flow using an appropriate reser
40、voir.13.2.3 Pump approximately 100 mL of water through theresin-packed column and check the final effluent pH with pHpaper. Repeat the wash if the test indicates residual activity. Besure to leave approximately 25 mL of water standing on top ofthe resin bed in the glass column or be certain that the
41、 feed tuberemains full of water in order to prevent air from entering theresin bed before the sample reaches the column.13.2.4 Place the flexible PVC inlet tube into the samplecontainer. It may be desirable to attach a 250 to 300-mm lengthof glass tubing to the sample container end of the PVC tofaci
42、litate removal of the sample from the container.13.2.5 Place the pump discharge tube into a beaker or bottleto collect the column effluent.13.2.6 Start the pump and vary the speed control to give aflow rate of 40 mL/min.NOTE 6It is necessary to calibrate the variable speed control of theperistaltic
43、pump by timing the flow of known liquid quantities at eachsetting of the control.13.2.7 When the sample container is empty, remove theupper stopper, and glass wool plug from the top of the columnand pour the resin into a 600-mL beaker.13.2.8 Wash the resin with three successive 100-mL por-tions of w
44、ater. Stir briefly and allow the resin to settle to thebottom of the beaker. Decant and discard the wash water.13.2.9 Place a magnetic stirring bar in the beaker with thewashed resin and add 250 mL of 5 to 6 % NaOCl. Place thebeaker on a magnetic stirrer and stir for 10 min.Allow the resinto settle.
45、 Filter the NaOCl solution by suction through a glassfiber filter supported in a sintered glass Bchner-type funnel.Save the filtrate.NOTE 7The NaOCl solution oxidizes the iodide absorbed on the resinto periodate which is released to the solution.13.2.10 Add 250 mLof fresh 5 to 6 % NaOCl solution to
46、theresin remaining in the beaker and stir for another 10 min.Allow the resin to settle and filter the NaOCl solution into theBchner funnel. Save the filtrate.13.2.11 Add 50 mL of water solution to the resin remainingin the beaker and stir for 5 min. Filter the solution and resininto the Bchner funne
47、l and rinse the resin thoroughly withwater. Save the filtrate. Transfer the NaOCl solution from thisstep and 13.2.10 and 13.2.11 into a 2000-mL beaker anddiscard the resin.NOTE 8Precaution: Chlorine Gas Released. Acidification of the6Firestone, R.B. and Shirley, V.S., Table of the Isotopes, (Eighth
48、Edition), JohnWiley and Sons, Inc., New York, 1996.FIG. 1 Iodine Procedure: Ion ExchangeD 4785 00a3residual NaOCl decomposes it, releasing chlorine gas (green color) whichis highly toxic. This destroys residual NaOCl which would interfere in thereduction of iodate to elemental iodine. All subsequent
49、 steps through13.2.16 are to be performed in a well-ventilated fume hood.13.2.12 In an adequate fume hood, slowly add concentratedHNO3(sp gr 1.42) to the NaOCl solution from 13.2.11 untilthe pH is brought to 1. (Approximately 45 mL of HNO3arerequired.) Stir magnetically until the bulk of the chlorine gashas evolved from the solution.13.2.13 Pour the acidified solution into a 1000-mL separa-tory funnel containing 100 mL of toluene and2gofNH2OHHCl.NOTE 9Hydroxylamine hydrochloride is a mild reducing agent ca-pable of reducing iodate to iodine (
