RESUMO
This paper presents a fast and automatic flow-based method to extract 131I from biological samples and hospital waste, previous to liquid scintillation detection. 131I is a radionuclide extensively used in Nuclear Medicine due to their beta and gamma disintegrations, whereby hospitals have to manage the associated waste generation. The automatic developed system is based on Lab-On-Valve (LOV) flow-technique exploiting Cl-resin (135â¯mg per extraction). This methodology allows performing sample extractions and measurements on the same day, since the extraction frequency takes 1.4-4 h-1, depending on the analysed sample volume, plus up to 2â¯h of measurement for each vial. 131I is retained as iodine ion and eluted with sodium sulphide 0.2â¯molâ¯L-1. The maximum sample volume that can be preconcentrated is 20â¯mL, reaching an extraction efficiency of 85⯱â¯5%. The minimum detectable activity (MDA) is 0.05 Bq, showing a precision of 7% RSD (nâ¯=â¯5). Both, biological samples (urine and saliva) and hospital waste samples can be satisfactorily analysed by the proposed system, obtaining recoveries between 90 and 110%. The developed method is then suitable to implement in hospitals, improving the surveillance of the 131I environmental release.
Assuntos
Análise de Injeção de Fluxo/métodos , Hospitais/provisão & distribuição , Radioisótopos do Iodo/análise , Resíduos de Serviços de Saúde/análise , Contagem de Cintilação/métodos , Humanos , Radioisótopos do Iodo/urina , Saliva/químicaRESUMO
An automatic system based on multisyringe flow injection analysis (MSFIA) and lab-on-valve (LOV) flow techniques for separation and pre-concentration of (226)Ra from drinking and natural water samples has been developed. The analytical protocol combines two different procedures: the Ra adsorption on MnO2 and the BaSO4 co-precipitation, achieving more selectivity especially in water samples with low radium levels. Radium is adsorbed on MnO2 deposited on macroporous of bead cellulose. Then, it is eluted with hydroxylamine to transform insoluble MnO2 to soluble Mn(II) thus freeing Ra, which is then coprecipitated with BaSO4. The (226)Ra can be directly detected in off-line mode using a low background proportional counter (LBPC) or through a liquid scintillation counter (LSC), after performing an on-line coprecipitate dissolution. Thus, the versatility of the proposed system allows the selection of the radiometric detection technique depending on the detector availability or the required response efficiency (sample number vs. response time and limit of detection). The MSFIA-LOV system improves the precision (1.7% RSD), and the extraction frequency (up to 3 h(-1)). Besides, it has been satisfactorily applied to different types of water matrices (tap, mineral, well and sea water). The (226)Ra minimum detectable activities (LSC: 0.004 Bq L(-1); LBPC: 0.02 Bq L(-1)) attained by this system allow to reach the guidance values proposed by the relevant international agencies e.g. WHO, EPA and EC.