Comparison and validation of methods for the determination of ⁹⁰Sr by Cerenkov counting in biological and sediment samples, including green chemistry metrics

In this work, a comparative study of two popular radiochemical procedures for ⁹⁰Sr determination in biological and sediment samples via Cerenkov counting was performed. Comparative tests were carried out with a Liquid Scintillation Counter (LSC) and several key factors related to green analytical chemistry were considered. Chemical yields, time of analysis, cost per sample, hazardous reagents used (H-factor), wastes generated (E-factor) and energy consumed (Q-factor) were calculated. The separation methods are based on two contrasted extraction mechanisms: chromatographic extraction (using Sr resin, a crown-ether diluted in octanol) and liquid–liquid solvent extraction (using HDEHP, an organophosphorus compound), where the chromatographic extraction method was optimized. The developed analytical procedure based on HDEHP was cheaper and faster than the analytical procedure based on Sr resin, according to the green chemistry. On the other hand, the Sr resin method provided a minimum detectable activity (MDA) of 1.1 Bq kg⁻¹, lower than 1.5 Bq kg⁻¹ corresponding to HDEHP method, due to the higher capacity of sample that can be loaded into the resin. The accuracy and reproducibility of both methods was confirmed in the analysis of certified reference materials provided by the International Atomic Energy Agency (IAEA).