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Title: Quantification of Technetium-99 in Complex Groundwater Matrixes using a Radiometric Preconcentrating Minicolumn Sensor in an Equilibration-based Sensing Approach

Abstract

A preconcentrating minicolumn sensor for pertechnetate detection in water consists of a packed bed containing a mixture of anion exchange resin and scintillating plastic beads. The column materials are contained in a transparent plastic flow cell placed between two photomultiplier tubes for radiometric detection. Upon retention of pertechnetate anions, the radioactive decay of Tc-99 results in detectable scintillation pulses that are counted in coincidence. In equilibration-based sensing mode, the sample is pumped through the packed bed until complete chromatographic equilibrium is achieved between the activity concentration in the water sample and the concentration on the anion exchange resin. The analytical signal is the observed steady state count rate at equilibrium. The sensitivity is related to a measurement efficiency parameter that is the product of the retention volume and the absolute radiometric detection efficiency. This sensor can readily detect pertechnetate to levels ten times below the drinking water standard of 0.033 Bq/mL. The potential for other anions in natural groundwater and contaminated groundwater plumes to interfere with pertechnetate detection and quantification have been examined in detail, with reference to the groundwater chemistry at the Hanford Site in Washington State. Individual anions such as nitrate, carbonate, chloride and iodide, at natural ormore » elevated concentrations, do not interfere significantly with pertechnetate uptake on the anion exchange resin. Elevated chromate or sulfate anion concentrations can interfere with pertechnetate uptake by the resin, but only at levels substantially higher than typical concentrations in groundwater or contamination plumes. Nevertheless, elevated anion concentrations may reduce pertechnetate uptake and sensitivity of the sensor when present in combination. Chromate is retained on the anion exchange resin from water at ppb levels, leading to an orange stain that interferes with pertechnetate detection by the absorption of scintillation light pulses (color quench). Radioactivity from radioiodine, tritium, and uranium are not expected to create a significant positive bias in groundwater analyses. A method of automated fluidic standard addition is demonstrated that corrects for matrix interferences leading to accurate analyses over a wide range of groundwater compositions.« less

Authors:
; ;
Publication Date:
Research Org.:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org.:
USDOE
OSTI Identifier:
948398
Report Number(s):
PNNL-SA-62996
30400; KP1504010; TRN: US0901615
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Journal Name:
Analytical Chemistry, 81(3):1068-1078
Additional Journal Information:
Journal Volume: 81; Journal Issue: 3
Country of Publication:
United States
Language:
English
Subject:
38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY; 54 ENVIRONMENTAL SCIENCES; GROUND WATER; RADIOCHEMICAL ANALYSIS; TECHNETIUM 99; ION EXCHANGE; EXTRACTION COLUMNS; RADIOMETRIC ANALYSIS; COINCIDENCE METHODS; SENSITIVITY; PERTECHNETATES; PHOTOMULTIPLIERS; Environmental Molecular Sciences Laboratory

Citation Formats

O'Hara, Matthew J, Burge, Scott R, and Grate, Jay W. Quantification of Technetium-99 in Complex Groundwater Matrixes using a Radiometric Preconcentrating Minicolumn Sensor in an Equilibration-based Sensing Approach. United States: N. p., 2009. Web. doi:10.1021/ac8021604.
O'Hara, Matthew J, Burge, Scott R, & Grate, Jay W. Quantification of Technetium-99 in Complex Groundwater Matrixes using a Radiometric Preconcentrating Minicolumn Sensor in an Equilibration-based Sensing Approach. United States. doi:10.1021/ac8021604.
O'Hara, Matthew J, Burge, Scott R, and Grate, Jay W. Sun . "Quantification of Technetium-99 in Complex Groundwater Matrixes using a Radiometric Preconcentrating Minicolumn Sensor in an Equilibration-based Sensing Approach". United States. doi:10.1021/ac8021604.
@article{osti_948398,
title = {Quantification of Technetium-99 in Complex Groundwater Matrixes using a Radiometric Preconcentrating Minicolumn Sensor in an Equilibration-based Sensing Approach},
author = {O'Hara, Matthew J and Burge, Scott R and Grate, Jay W},
abstractNote = {A preconcentrating minicolumn sensor for pertechnetate detection in water consists of a packed bed containing a mixture of anion exchange resin and scintillating plastic beads. The column materials are contained in a transparent plastic flow cell placed between two photomultiplier tubes for radiometric detection. Upon retention of pertechnetate anions, the radioactive decay of Tc-99 results in detectable scintillation pulses that are counted in coincidence. In equilibration-based sensing mode, the sample is pumped through the packed bed until complete chromatographic equilibrium is achieved between the activity concentration in the water sample and the concentration on the anion exchange resin. The analytical signal is the observed steady state count rate at equilibrium. The sensitivity is related to a measurement efficiency parameter that is the product of the retention volume and the absolute radiometric detection efficiency. This sensor can readily detect pertechnetate to levels ten times below the drinking water standard of 0.033 Bq/mL. The potential for other anions in natural groundwater and contaminated groundwater plumes to interfere with pertechnetate detection and quantification have been examined in detail, with reference to the groundwater chemistry at the Hanford Site in Washington State. Individual anions such as nitrate, carbonate, chloride and iodide, at natural or elevated concentrations, do not interfere significantly with pertechnetate uptake on the anion exchange resin. Elevated chromate or sulfate anion concentrations can interfere with pertechnetate uptake by the resin, but only at levels substantially higher than typical concentrations in groundwater or contamination plumes. Nevertheless, elevated anion concentrations may reduce pertechnetate uptake and sensitivity of the sensor when present in combination. Chromate is retained on the anion exchange resin from water at ppb levels, leading to an orange stain that interferes with pertechnetate detection by the absorption of scintillation light pulses (color quench). Radioactivity from radioiodine, tritium, and uranium are not expected to create a significant positive bias in groundwater analyses. A method of automated fluidic standard addition is demonstrated that corrects for matrix interferences leading to accurate analyses over a wide range of groundwater compositions.},
doi = {10.1021/ac8021604},
journal = {Analytical Chemistry, 81(3):1068-1078},
number = 3,
volume = 81,
place = {United States},
year = {2009},
month = {2}
}