MSFIA-LOV system for 226Ra isolation and pre-concentration from water samples previous radiometric detection

• Automatic, rapid and selective method for 226Ra extraction/pre-concentration from water.
• MSFIA-LOV system performs a sample clean-up prior to 226Ra radiometric detection.
• 226Ra sample preparation allows using two radiometric detectors (LBPC and LSC).
• Environmental levels of 226Ra are easily quantified.
• High sensitivity and selectivity are achieved, reaching the 226Ra regulations for drinking water.

An automatic system based on multisyringe flow injection analysis (MSFIA) and lab-on-valve (LOV) flow techniques for separation and pre-concentration of 226Ra 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 226Ra 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 226Ra 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.

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