ASTM D4785-08(2013)e1
(Test Method)Standard Test Method for Low-Level Analysis of Iodine Radioisotopes in Water
Standard Test Method for Low-Level Analysis of Iodine Radioisotopes in Water
SIGNIFICANCE AND USE
5.1 This test method was developed for measuring low levels of radioactive iodine in water. The results of the test may be used to determine if the concentration of several radioisotopes of iodine in the sample exceeds the regulatory statutes for drinking water. With a suitable counting technique, sample size, and counting time, a detection limit of less than 0.037 Bq/L (1 pCi/L) is attainable by gamma-ray spectroscopy. This method was tested for 131I . Other iodine radioisotopes should behave in an identical manner in this procedure. However, other iodine radioisotopes have not been tested according to Practice D2777. The user of this method is responsible for determining applicability, bias, and precision for the measurement of other iodine radioisotopes using this method.
5.2 This procedure addresses the analysis of iodine radioisotopes with half-lives greater than 2 hours, which include 121I, 123I, 124I, 125I, 126I, 129I, 130I, 131I, 132I, 133I, and 135I.
SCOPE
1.1 This test method covers the quantification of low levels of radioactive iodine in water by means of chemical separation and counting with a high-resolution gamma ray detector. Iodine is chemically separated from a 4-L water sample using ion exchange and solvent extraction and is then precipitated as cuprous iodide for counting.
1.2 The values stated in SI units are to be regarded as standard. The values given in parentheses are provided for information purposes only.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. For specific hazard statements, see 8.17, 8.18, 8.19, Section 9, and 13.2.11.
General Information
Relations
Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
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Designation: D4785 − 08 (Reapproved 2013)
Standard Test Method for
Low-Level Analysis of Iodine Radioisotopes in Water
This standard is issued under the fixed designation D4785; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
ε NOTE—Warning notes were editorially updated throughout in June 2013.
1. Scope D3649PracticeforHigh-ResolutionGamma-RaySpectrom-
etry of Water
1.1 This test method covers the quantification of low levels
D5847Practice for Writing Quality Control Specifications
ofradioactiveiodineinwaterbymeansofchemicalseparation
for Standard Test Methods for Water Analysis
and counting with a high-resolution gamma ray detector.
D3856Guide for Management Systems in Laboratories
Iodine is chemically separated from a 4-L water sample using
Engaged in Analysis of Water
ion exchange and solvent extraction and is then precipitated as
cuprous iodide for counting.
3. Terminology
1.2 The values stated in SI units are to be regarded as
3.1 Definitions—For definitions of terms used in this test
standard. The values given in parentheses are provided for
method, refer to Terminology D1129.
information purposes only.
4. Summary of Test Method
1.3 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
4.1 Sodium iodide is added as a carrier prior to performing
responsibility of the user of this standard to establish appro-
any chemical separations. The samples undergo an oxidation-
priate safety, health, and environmental practices and deter-
reduction process to ensure exchange between the carrier and
mine the applicability of regulatory limitations prior to use.
the radioactive iodide. Hydroxylamine hydrochloride and so-
For specific hazard statements, see 8.17, 8.18, 8.19, Section 9,
dium bisulfite are added to convert all the iodine to iodide
and 13.2.11.
which is then removed by anion exchange. Subsequent elution
1.4 This international standard was developed in accor-
of the iodide is followed by oxidation-reduction to elemental
dance with internationally recognized principles on standard-
iodine. The elemental iodine is purified by solvent extraction,
ization established in the Decision on Principles for the
reduced to iodide, and precipitated as cuprous iodide. The
Development of International Standards, Guides and Recom-
chemical recovery is determined from the recovery of the
mendations issued by the World Trade Organization Technical
iodide carrier.
Barriers to Trade (TBT) Committee.
5. Significance and Use
2. Referenced Documents
5.1 This test method was developed for measuring low
2.1 ASTM Standards:
levelsofradioactiveiodineinwater.Theresultsofthetestmay
D1129Terminology Relating to Water
be used to determine if the concentration of several radioiso-
D1193Specification for Reagent Water
topesofiodineinthesampleexceedstheregulatorystatutesfor
D2777Practice for Determination of Precision and Bias of
drinking water. With a suitable counting technique, sample
Applicable Test Methods of Committee D19 on Water
size, and counting time, a detection limit of less than 0.037
D3370Practices for Sampling Water from Closed Conduits
Bq/L (1 pCi/L) is attainable by gamma-ray spectroscopy. This
D3648Practices for the Measurement of Radioactivity
method was tested for I . Other iodine radioisotopes should
behave in an identical manner in this procedure. However,
other iodine radioisotopes have not been tested according to
This test method is under the jurisdiction ofASTM Committee D19 on Water
Practice D2777. The user of this method is responsible for
andisthedirectresponsibilityofSubcommitteeD19.04onMethodsofRadiochemi-
cal Analysis.
determining applicability, bias, and precision for the measure-
Current edition approved June 15, 2013. Published July 2013. Originally
ment of other iodine radioisotopes using this method.
approved in 1988. Last previous edition approved in 2008 as D4785–08. DOI:
10.1520/D4785-08R13E01.
5.2 This procedure addresses the analysis of iodine radio-
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
isotopes with half-lives greater than 2 hours, which include
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
121 123 124 125 126 129 130 131 132 133
I, I, I, I, I, I, I, I, I, I, and
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. I.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
´1
D4785 − 08 (2013)
6. Interferences 8.4 Ammonium Hydroxide (sp gr 0.90)—Concentrated am-
monium hydroxide (NH OH).
6.1 Stable iodine in the sample will interfere with the
chemical recovery determination. One milligram of ambient 8.5 Ammonium Hydroxide (1.4 M)—Mix one volume of
iodine would produce a bias of about −4%. concentrated NH OH (sp gr 0.90) with nine volumes of water.
6.2 There are numerous characteristic iodine X-rays at and 8.6 Anion Exchange Resin—Strongly basic, styrene, quar-
below 33.6 keV which are indicative of iodine, but not a ternary ammonium salt, 20–50 mesh, chloride form, Dowex
specific radioisotope of iodine. It is recommended that only 1-X8, or equivalent.
discreetgammaenergylinesatandabove35.5keVbeusedfor
8.7 Cuprous Chloride Solution(approximately10mgCuCl/
identification and quantification of iodine radioisotopes.
mL)—Dissolve 10 g of CuCl (99.99%) in 26 mL of concen-
trated HCl (sp gr 1.19).Add this solution to 1000 mLof NaCl
7. Apparatus
solution (1 M) slowly with continuous stirring. Add a small
7.1 Analytical Balance, readable to 0.1 mg.
quantity of metallic copper (for example, 5 to 10 copper metal
shot) to the solution for stabilization. Store the CuCl in a
7.2 Flexible Polyvinyl Chloride (PVC) Tubing,6.35mm( ⁄4
desiccator.
in.) outside diameter, 1-m length.
8.8 Hydrochloric Acid (sp gr 1.19)—Concentrated hydro-
7.3 Gamma-Ray Spectrometry System—High resolution
chloric acid (HCl).
gamma spectrometer (high purity germanium or equivalent)
with a useful energy range of approximately 30 keV to 1800
8.9 Hydrochloric Acid Solution (0.3 M)—Dilute 25 mL of
keV (see Practice D3649).
concentrated HCl to 1000 mL with water.
7.4 Glass Fiber Filter Paper, 11.5-cm diameter.
8.10 Hydroxylamine Hydrochloride (NH OH:HCl)—
Crystals.
7.5 Ion Exchange Column, glass tube, 35 6 2-mm inside
diameter, 150-mm length, fitted with No. 8 one-hole rubber
8.11 Iodide Carrier Solution(25mgI/mL)—Dissolve14.76
stoppers and perforated disk.
g of NaI in approximately 80 mL of water in a 500-mL
volumetric flask and dilute to volume. Standardize using the
7.6 Membrane Filters, 0.4 or 0.45-µm pore size, 25-mm
procedure in Section 10.
diameter, with suitable filter holder and vacuum filter flask.
8.12 Iodine-131 Standardizing Solution—National stan-
7.7 Peristaltic Tubing Pump, variable speed, fitted with
dardizing body such as National Institute of Standards and
vinyl or silicone tubing.
Technology (NIST), traceable solution with a typical concen-
7.8 pH Meter.
tration range from 1 to 10 kBq/mL.
7.9 Sintered Glass Filter, Büchner funnel, 150-mL size,
8.13 Nitric Acid (sp gr 1.42)—Concentrated HNO .
medium or coarse porosity with suitable one-hole stopper and
8.14 Nitric Acid (1.4 M)—Mix 1 volume of concentrated
vacuum filter flask.
HNO (sp gr 1.42) with 10 volumes of water.
7.10 Vacuum Desiccator.
8.15 SodiumBisulfiteSolution,(2M)—Dissolve104.06gof
7.11 Vortex Mixer.
NaHSO in approximately 300 mL of water in a 500-mL
volumetric flask and dilute to volume.
8. Reagents and Materials
8.16 Sodium Chloride Solution (1 M)—Dissolve 58.45 g of
8.1 Purity of Reagents—Reagent grade chemicals shall be
NaCl in approximately 500 mL of water in a 1000 mL
used in all tests. Unless otherwise indicated, it is intended that
volumetric flask and dilute to volume.
all reagents shall conform to the specifications of the Commit-
teeonAnalyticalReagentsoftheAmericanChemicalSociety.
8.17 Sodium Hydroxide Solution (12.5 M)—Dissolve 500 g
Othergradesmaybeusedprovidedtheyareofsufficientlyhigh
of NaOH in 800 mL of water and dilute to 1 L. (Warning—
purity to permit their use without reducing the accuracy of the
The dissolution of sodium hydroxide may produce excessive
determination.
heat.)
8.2 Purity of Water—Unless otherwise indicated, reference
8.18 Sodium Hypochlorite (NaOCl)—Approximately 5 to
towatershallbeunderstoodtomeanreagentwaterconforming
6 %. Commercially available bleach is acceptable.
to Specification D1193, Type III.
(Warning—Acidification of NaOCl produces toxic chlorine
gas and must be handled in a fume hood.)
8.3 Radioactive Purity—Radioactive purity shall be such
that the measured radioactivity of blank samples does not
8.19 Toluene.(Warning—Tolueneisacarcinogenandmust
exceed the calculated probable error of the measurement.
be handled and disposed of in an approved manner.)
Reagent Chemicals, American Chemical Society Specifications, American
4 +2
Chemical Society, Washington, DC. For Suggestions on the testing of reagents not CuCl solution is not stable. It can be oxidized to the Cu state by air after a
listed by the American Chemical Society, see Annual Standards for Laboratory period of time, when the solution will turn dark green. If this happens, prepare a
Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia fresh solution. The shelf life of the solution can be extended by displacing the air
and National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville, over the remaining solution with nitrogen or argon gas after each use and then
MD. closing the container promptly.
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D4785 − 08 (2013)
125 129
8.20 CalibrationStandard(s)—Knownamountsof I, I, En 5 Offset1 Ch 3Slope (1)
~ !
and I are used for calibration when determining these
where:
radionuclides. A mixed-gamma standard, for ex-
241 109 57 141 113 137 88 60 En = peak energy (keV),
ample, Am, Cd, Co, Ce, Sn, Cs, Y, and Co,
Offset = energy offset for the energy calibration equation
is used for calibration over an extended energy range as
(keV),
required for the determination of additional radioisotopes of
Ch = peak location channel number, and
iodine. These standards should be mounted on the filter as
Slope = energy calibration equation slope (keV per chan-
describedin7.6.Theknownamountsoftheradionuclidesmust
nel).
be traceable to a national standardizing body such as NIST in
NOTE 1—Most modern spectroscopy software packages perform this
the USA. The standard may be prepared by the laboratory
calculation,andmayincludehigher-orderpolynomialtermstoaccountfor
performing this method or by a commercial supplier of such
minor non-linearity in the energy calibration.
standards.Alternate radionuclides may be used for calibration
11.3 Using the gamma emission data from the calibration
providedthattheyhavegammarayenergiescoveringtherange
standard and the peak resolution data from the calibration
of interest for the iodine radionuclides to be analyzed.
spectrum, establish the resolution versus energy relationship
9. Hazards (energy calibration) as:
9.1 Due to the potential health effects from handling these FWHM 5 Offset1 Ch 3Slope (2)
~ !
compounds, the steps utilizing NaOCl and toluene must be
where:
carried out in a fume hood. Toluene is a carcinogen and
FWHM = full width of the peak at one-half the maximum
acidification of NaOCl liberates toxic Cl gas.
counts in the centroid channel (keV),
10. Standardization of Iodide Carrier
Offset = widthoffsetfortheresolutioncalibrationequation
(keV),
10.1 Pipet 1.0 mLof iodide carrier reagent into each of five
En = peak energy (keV), and
100-mLcentrifuge tubes containing 50 mLof deionized water.
Slope = resolution calibration equation slope (keV/keV).
10.2 Add 0.1 mL of 2 M NaHSO to each solution and stir
NOTE 2—Most modern spectroscopy software packages perform this
vigorously using a vortex mixer. Add 5.0 mL of freshly
calculation,andmayincludehigher-orderpolynomialtermstoaccountfor
prepared CuCl solution.
non-linearity in the resolution calibration.
10.3 Using a pH meter, check the pH of each solution and
11.4 For each gamma-ray photopeak, calculate the full-
adjustthepHtobetween2.40to2.50with0.3 MHClor1.4 M
energy peak efficiency, ε, as follows:
f
NH OH.
R
n
ϵ 5 (3)
f
10.4 Place each solution in a warm (approximately 50 to
R 3DF
γ
60°C) water bath for 5 to 10 min, stirring occasionally.
where:
10.5 Rinse each CuI precipitate onto a separate preweighed
ε = full-energy peak efficiency (counts per gamma ray
f
0.45-µm membrane filter mounted in a vacuum filtration
emitted),
assembly. Rinse the walls of the filter holder with approxi-
R = net gamma-ray count rate in the full-energy peak of
n
mately 50 mL of water.
–1
interest, counts per second (s ),
10.6 Dryallsamplesinavacuumdesiccatorforaminimum
R = gamma-ray emission rate, in gamma-rays per second
γ
–1
of 60 min or to constant weight. Remove and weigh the filter
(s ), as of the reference date and time of the
and precipitate. Record all data.
calibration standard,
–λ(t –t
1 0
DF = decay factor for the calibrating radionuclide, e ),
10.7 Determine the net weight of each CuI precipitate.
λ = (ln 2) / t ,
1/2
10.8 Use the mean of the five weights for the standard
t = half-life of calibrating radionuclide (half-life unit
1/2
weight.The relative standard deviation of the mean should not
must match that used for the time difference, t –t ),
1 0
exceed 0.025.
t = reference date and time of the calibration standard,
and
11. Calibration of High-Resolution Gamma-Ray
t = midpoint of sample count (date and time).
Spectroscopy System
11.5 Many modern spectrometry systems are computerized
11.1 Accumulate an energy spectrum using the calibration
and the determination of the gamma-ray detection efficiencies
standard (8.20) traceable to a national standards body, in the
is performed automatically at the end of an appropriate
geometrical position representing that of the samples to be
counting interval. Refer to the manufacturer instructions for
analyzed.Accumulate sufficient net counts (total counts minus
specific requirements and capabilities.
the Compton baseline) in each full-energy gamma-ray peak of
interest to obtain a relative standard counting uncertainty of
11.6 Plot the values for the full-energy peak efficiency (as
≤1%.
determined in Section 11.5) versus gamma-ray energy. Com-
11.2 Using the gamma-ray emission data from the calibra- pare the efficiency curve to the typical efficiency curve for the
tion sta
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