ASTM: D4785: Low-Level Iodine-131 in Water

Summary
Analytes
Revision
Data and Sites

Official Method Name

Standard Test Method for Low-Level Iodine-131 in Water

Current Revision

Current edition approved July 10, 2000. Originally published as D4785-88.

Media

WATER

Instrumentation

Gamma Radiation Detector

Method Subcategory

Radiochemical

Method Source

ASTM

Citation

Annual Book of ASTM Standards, Section 11, Water and Environmental Technology, Volume 11.02, Water (I)

Brief Method Summary

Sodium iodide is added as a carrier prior to performing any chemical separations. The samples undergo an oxidation-reduction process to ensure exchange between the carrier and the radioactive iodide. Hydroxylamine hydrochloride and sodium bisulfite are added to convert all the iodine to iodide which is then removed by anion exchange. Subsequent elution of the iodide followed by oxidation-reduction yields elemental iodine. The elemental iodine is purified by solvent extraction, reduced to iodide, and precipitated as cuprous iodide. The chemical yield is determined from the recovery of the iodide carrier.

Scope and Application

This test method covers the quantification of low levels of iodine-131 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.

Applicable Concentration Range

> 0.037 Bq/L

Interferences

Stable iodine in the sample will interfere with the chemical yield determination. One milligram of iodine would produce a bias of about -4 %.

Quality Control Requirements

Prior to using this test method, a quality control (QC) program for the instrumentation (high-resolution gamma-ray spectrometer) shall be established when the system is calibrated. Quality control or tolerance charts shall be established. Control limits shall be established with corrective actions when control limits are exceeded.
The project manager, as part of the external quality control program, shall submit blind quality control samples to the analysts along with routine samples. The quality control samples that are routinely used include blank samples, replicate samples, reference material, and spiked samples.

Sample Handling

Collect a sample in accordance with Practice D 3370.

Maximum Holding Time

Relative Cost

Unknown

Sample Preparation Methods

This method has 1 analyte associated with it.

Analyte	Detection Level	Bias	Precision	Pct False Positive	Pct False Negative	Spiking Level
Iodine-131(10043-66-0) Iodine-131	0.037 Bq/L	104% Rec (ML)	14.70 % RSD (ML)			0.74 Bq/L

Precision Descriptor Notes:	The collaborative test conducted of this test method included 6 laboratories each with one operator. Three activity levels between 0.74 Bq/L (20 pCi/L) and 149 Bq/L (4020 pCi/L) were tested with three replicates per level. The determination of the precision and bias statements were made in accordance with Practice D 2777. NOTE: These collaborative test data were obtained using reagent grade water.
Detection Level Note:	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.

Precision Descriptor Notes:

The collaborative test conducted of this test method included 6 laboratories each with one operator. Three activity levels between 0.74 Bq/L (20 pCi/L) and 149 Bq/L (4020 pCi/L) were tested with three replicates per level. The determination of the precision and bias statements were made in accordance with Practice D 2777. NOTE: These collaborative test data were obtained using reagent grade water.

Detection Level Note:

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.

Revision	PDF/Link
Current edition approved July 10, 2000. Originally published as D4785-88.

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ASTM: D4785: Low-Level Iodine-131 in Water

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