Fast-response flow-based method for evaluating 131I from biological and hospital waste samples exploiting liquid scintillation detection.

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 (135 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 2 h of measurement for each vial. 131I is retained as iodine ion and eluted with sodium sulphide 0.2 mol L-1. The maximum sample volume that can be preconcentrated is 20 mL, reaching an extraction efficiency of 85 ±â€¯5%. The minimum detectable activity (MDA) is 0.05 Bq, showing a precision of 7% RSD (n = 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.