|Year : 2012 | Volume
| Issue : 2 | Page : 77-79
Estimation of uranium isotope in urine samples using extraction chromatography resin
Smita S Thakur1, Jogendra Yadav1, Devender Rao2
1 Health Physics Laboratory, GSO Complex, Bhabha Atomic Research Centre, Tarapur, India
2 Internal Dosimetry Section, Health Physics Division BARC, Trombay, Mumbai, Maharashtra, India
|Date of Web Publication||21-May-2013|
Internal Dosimetry Section, Health Physics Division BARC, Trombay, Mumbai - 400 094
Source of Support: None, Conflict of Interest: None
Introduction: Internal exposure monitoring for alpha emitting radionuclides is carried out by bioassay samples analysis. For occupational radiation workers who handle uranium in reprocessing or fuel fabrication facilities, there exist a possibility of internal exposure and urine assay is the preferred method for monitoring such exposure. Materials and Methods: Separation of Uranium is carried out by extraction chromatography using diamyl amyl phosphonate (U/TEVA) resin. This resin contains diamyl amyl phosphonate extractant supported on inert Amberlite XAD-7 (an acrylic ester) resin.The electrodeposited samples are counted using octet alpha spectrometery. Results and Discussion: The analysis time involved from sample loading to stripping is 2 h compared with the 3.5 h involved in conventional ion exchange method. The radiochemical yield was found in the range of 69-91%. Minimum detectable activity for uranium estimation for 3,60,000 s counting time at an average percentage recovery of 82 8 works out to 0.21 mBq/d. Conclusion: The technique gives good and consistent radiochemical yield of 82% on repeated use of the chromatographic column when compared with ion exchange technique. Analysis time involved from sample loading to stripping using UTEVA is 2 h compared with the time involved of 3.5 h by the conventional ion exchange method.
Keywords: Extraction chromatography, minimum detectable activity, bioassay alpha spectrometry, U/TEVA resin
|How to cite this article:|
Thakur SS, Yadav J, Rao D. Estimation of uranium isotope in urine samples using extraction chromatography resin. Radiat Prot Environ 2012;35:77-9
|How to cite this URL:|
Thakur SS, Yadav J, Rao D. Estimation of uranium isotope in urine samples using extraction chromatography resin. Radiat Prot Environ [serial online] 2012 [cited 2022 Jan 19];35:77-9. Available from: https://www.rpe.org.in/text.asp?2012/35/2/77/112345
| Introduction|| |
Exposure to uranium can result in both chemical and radiological toxicities. The main chemical effect associated with exposure to uranium and its soluble compound is kidney toxicity.
Uranium is one of the densest material known (19 g/cm 3 ), being 1.6 times more dense than lead. Once in the bloodstream, the uranium compounds are filtered by the kidneys, where they can cause damage to the kidney cells. Very high uranium intake (ranging from about 50 to 150 mg depending on the individual) can cause acute kidney failure leading to death. At lower intake levels (around 25-40 mg), damage can be detected by the presence of protein and dead cells in the urine.  During the routine plant operation incidentally/accidentally, uranium may become air borne and pose inhalation hazard to occupational radiation workers in fuel reprocessing and fuel fabrication facilities. There are many analytical methods available to estimate internally deposited uranium isotopes at low level like, neutron activation analysis technique, mass spectrometry, fission track analysis,  and laser fluorometry. This paper deals with the use of extraction chromatographic resin and alpha spectrometric technique for the estimation of uranium in urine samples.
Most of the uranium absorbed into blood is rapidly excreted, mainly in urine. Of the total uptake of uranium, about 65% is excreted during the 1 st day, another 10% during the rest of the 1 st week. There is a continuous slow excretion, about 0.002% of the original uptake to blood per day after a year in urine. Therefore to estimate internally deposited uranium, urine bioassay is the preferred technique. The uranium that is not rapidly excreted gets deposited in various organs and about 10% in kidneys. Since the kidneys' weight is relatively small, the specific activity concentration will be higher than the other organs.
In this paper, the method is described to separate uranium in urine using extraction chromatography and its analysis using alpha spectrometry.
| Materials and Methods|| |
The urine samples collected from non-radiation workers were spiked with 232 U tracer at mBq level to study the chemical yield. Ten such samples were spiked with 232 U tracer activity in the range of 7.5-22.5 mBq. The samples were wet oxidized with Conc. HNO 3 and H 2 O 2 . Uranium along with transuranics such as Am, Pu, and Sr if present gets co-precipitated along with calcium phosphate (Ca 3 (PO4) 2 ). The supernatant was discarded, precipitate was centrifuged, dissolved in Conc. HNO 3 , and allowed to evaporate until dry, repeatedly 2-3 times to destroy any leftover organic matter present in it. Residue dissolved in 10 ml of 1 M Al (NO 3 ) 3 prepared in 3 M HNO 3 . solution is filtered through whatman filter paper No. 41 (25 μm) to remove any insoluble residue and is ready for uranium loading on extraction chromatography column.
Extraction chromatography column preparation
U/TEVA resin of particle size of 100-150 μm was supported on inert material, Amberlite XAD-7. Slurry of this resin was made in distilled water and transferred to a glass column of diameter 0.6 cm and height, 6 cm. The resin bed volume was maintained at 2 ml capacity.
Separated solution containing uranium was loaded on extraction chromatography column, pre-conditioned with 3 M HNO 3 , at the rate of 0.5 mL/min. The column was washed with 10 ml 3 M HNO 3 at the rate of 0.5 mL/min. The column was rinsed with 5 ml of 9 M HCl followed by 20 ml of 0.05 M oxalic acid prepared in 5 M HCl. These two rinses are required to remove the interference of thorium and neptunium  if present in the sample. Uranium was then eluted with 25 ml of 0.01 M HCl at the rate of 0.5 ml/min. Eluted U fraction was electrodeposited on stainless steel planchet in ammonium sulfate medium at 2.2 pH, 300 mA current for 2 h. Electrodeposited samples were counted for 86,400 s by an octete alpha spectrometry system having PIPS semiconductor detector to estimate uranium recovery.
Extraction equilibrium reaction occurring between uranium and extractant as per following Eq.:
| Results and Discussion|| |
[Figure 1] gives the alpha spectra of a bioassay sample spiked with 8 mBq of 232 U counted for 86,400 s. [Table 1] lists the activity of 232 U spiked and recovered from urine sample using the procedure mentioned above. It is observed from [Table 1], that the radiochemical yield ranged from 69% to 95% with an average recovery of 82%. Whereas with conventional ion exchange technique, the average chemical recovery with calcium phosphate co-precipitation method was found to be 60%  and with hydrous titanium oxide co-precipitation method, chemical recovery had been observed to be 76%.  Approximate time involved in the analysis from sample loading to stripping is 2 h when compared with the time involved of 3.5 h by conventional ion exchange method. The radiochemical recovery obtained for U separation by this technique is comparable to that obtained by other researchers , in the field.
|Figure 1: Typical 232U spectrum obtained with octet alpha spectrometry system|
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During this work, an experiment was conducted to optimize eluent volume for maximizing uranium recovery. Urine sample from a non-radiation worker all sample analysed for this study were from non radiation workers was spiked with 232 U tracer having activity Conc. of 41.67 mBq. Uranium from the sample matrix was then pre-concentrated by calcium phosphate co-precipitation and loaded on U/TEVA extraction chromatography resin. Uranium elution from the column was carried out by taking 5 ml of elution volume each time from the total defined volume of 25 ml to observe elution pattern. [Table 2] shows the activity eluted at 5 ml differential volume of 0.01 M HCl.
|Table 2: Elution volume of 0.01 M HCl required for complete recovery of uranium isotopes from the column|
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The experimental result has shown that, 20 ml of (0.01 M HCl elute is required to elute the loaded activity completely.(Purpose of elution study was to know total vol. required for complete elution of uranium from chromatography column as in some other study  15 ml elution volume was used which when replicated gave less than 70% recovery in our few initial experiments.)
| Conclusion|| |
Radiochemical procedure for estimation of Uranium in urine samples using UTEVA extraction chromatographic technique, alpha spectrometry, and 232 U tracer is presented in this paper. The technique gives good and consistent radiochemical yield of 82% on repeated use of the chromatographic column when compared with ion exchange technique. Analysis time involved from sample loading to stripping using UTEVA is 2 h compared with the time involved of 3.5 h by the conventional ion exchange method.
| Acknowledgment|| |
Authors sincerely acknowledge the consistent encouragement provided by Dr. P.K. Sarkar Head, Health Physics Division BARC, in carrying out this work under the planned project XI-N-R and D-06.05.
| References|| |
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[Table 1], [Table 2]