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ARTICLE
Year : 2010  |  Volume : 33  |  Issue : 3  |  Page : 135-136  

Radiochemical procedure for estimation of sulphur-35 in bioassay samples


Health Physics Division, Bhabha Atomic Research Centre, Trombay, Mumbai, India

Date of Web Publication22-Oct-2011

Correspondence Address:
Sanu S Raj
Health Physics Division, Bhabha Atomic Research Centre, Trombay, Mumbai
India
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Source of Support: None, Conflict of Interest: None


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  Abstract 

Occupational workers from Board of Radiation Isotopes and Technology (BRIT) are engaged in synthesis of various compounds of Sulphur-35 ( 35 S) for application in life sciences. There is a possibility of intake of 35 S by these workers during the course of their work. It is necessary to assess intake and assign internal dose to these workers following an inhalation of 35 S. Estimation of intake of 35 S, which is a pure beta emitter, involves analysis of urine samples collected from workers. The present study illustrates standardization of a radiochemical procedure for estimation of 35 S in bioassay samples of these workers using Liquid Scintillation Spectrometer (LSS). The radiochemical recovery achieved in the present study ranged from 80.4% to 98.8 % with an average of about 91.4 %. The method, standardized, can be adopted for bioassay monitoring of workers handling 35 S labeled compounds.

Keywords: Bioassay for 35 S, internal dose, liquid scintillation spectrometer


How to cite this article:
Raj SS, Sawant PD, Bhati S. Radiochemical procedure for estimation of sulphur-35 in bioassay samples. Radiat Prot Environ 2010;33:135-6

How to cite this URL:
Raj SS, Sawant PD, Bhati S. Radiochemical procedure for estimation of sulphur-35 in bioassay samples. Radiat Prot Environ [serial online] 2010 [cited 2022 May 20];33:135-6. Available from: https://www.rpe.org.in/text.asp?2010/33/3/135/86286


  1. Introduction Top


Sulphur - 35 ( 35 S) being a soft beta emitter with maximum energy of 167 keV and half-life of 87.4 days is used for diagnostic and therapeutic purposes. Board of Radiation Isotopes and Technology (BRIT) synthesizes compounds labeled with 35 S for application in life sciences. There is a possibility of intake of the radionuclide by workers handling 35 S labeled compounds and hence Atomic Energy Regulatory Board (AERB), India has recommended individual monitoring of these workers. 35 S is a low energy beta emitter, therefore in - vitro monitoring (urinalysis) is the preferred technique for internal dose assessment for these workers. For this purpose studies were taken - up to standardize a radiochemical procedure for the estimation of organic as well as inorganic 35 S in bioassay samples. Nine urine samples were spiked with 35 S to estimate the radiochemical recovery of the procedure. Standardization of this method is important for the determination of 35 S in urine, which can be used for internal radiation dose assessment.


  2. Materials and Methods Top


For conducting the spiking experiments, Sulphur - 35 as sulphate (96.2 MBq) was procured from BRIT, Vashi (SIGA-3937 M, Con No. 039). The stock solution was diluted with nitric acid to obtain a working standard of 1.74 Bqml -1 . Nine urine samples collected from occupational workers not handling 35 S labeled compounds were spiked with 35 S activity [Table 1]. The radiochemical procedure standardized was as follows. 10 ml of urine sample was transferred into a porcelain dish; 100mg of sulphate carrier (50 mg ml -1 ) and 5 ml of Benedict's reagent were added. The solution was evaporated to dryness under IR lamp and then heated over a burner at red-hot for 5 -10 mins. KClO 3 present in the Benedict's solution acted as a strong oxidizing agent and converted organic as well as inorganic sulfur to sulphate (SO 4 2- ) ions. The residue was then dissolved in 3M HCl and transferred to a centrifuge tube with water washings twice. The solution inside the centrifuge tube was heated by placing the tube in a boiling water bath for 15 mins. To the hot well-stirred solution, 10 ml of 0.2 M BaCl 2 was slowly added to precipitate SO 4 2- ions present in the solution as BaSO 4 . The solution was heated in water bath to precipitate BaSO4 in hot condition which helped in coagulation of the precipitate. The precipitate was then centrifuged, supernatant discarded, mixed with scintillation cocktail (Instagel), and 35 S beta activity was measured using Liquid Scintillation Counter (LSC) (Packard TRICARB 2900 TR) to determine the radiochemical recovery of the procedure.
Table 1: Radiochemical recovery of 35S in urine samples

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  3. Results and Discussion Top


In the spiking experiments, BaSO4 precipitate was slurred with water and added to Instagel cocktail, which lead to quenching and reduction in detection efficiency to about 38 % (Detection efficiency for unquenched 35 S is 95%). This quenched efficiency was used while computing the activity present in the spiked urine samples. The results of the analysis are listed in [Table 1]. The average recovery for 35 S by this method was about 91.4 ± 6.5 %. Minimum detectable activity (MDA) of this technique, based on the analysis of blank urine samples, was 44.1 BqL -1 . The average recovery and MDA observed in the present study is comparable with that observed internationally.


  4. Conclusion Top


Intakes of 35 S in radiation workers can be assessed by analysis of urine samples collected from the workers. The present study demonstrates the capability of the radiochemical procedure standardized for the estimation of 35 S in bioassay samples. The average radiochemical recovery for 35 S by this method is good (> 90 %) and the MDA achieved is about 44.1 BqL -1 . The method standardized is simple, less expensive, rapid and can be employed successfully for routine monitoring of occupational workers to estimate the intake and there from internal dose following an inhalation of 35 S.


  5. References Top


  1. Boecker B, Hall R, Inn K, Lawrence J, Ziemer P, Eisele G, et al. (1991) Current Status of bioassay procedures to detect and quantify previous exposures to radioactive materials Health Phys60(Suppl 1):45-100.
  2. Gacs I, Vargay Z, Csetenyi J (1977). A new decomposition technique for the determination of sulphur or sulphur-35 in organic compounds as sulphuric acid. Mikrochimica-Acta-Australia 3-4:107-19.
  3. Kramer GH, Joseph, Sidney (1984). The simultaneous analysis of chlorine-36, sulphur-35, and phosphorous-32 in urine. Canadian J Chem 62:2344-5.




 
 
    Tables

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Abstract
1. Introduction
2. Materials and...
3. Results and D...
4. Conclusion
5. References
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