Optimisation and Validation of a Multi-matrix Ultrasensible Radiochemical Method for the Determination of Radiostrontium in Solid Foodstuffs by Liquid Scintillation Counting

Radiostrontium is a radiotoxic isotope, chemically an analogue to calcium. For this reason, it may follow similar pathways to this essential nutrient, and it is considered an important contaminant of several food supply chains. Different analytical methods are currently available for the determination of radiostrontium; however, they were optimised especially for the determinations in liquid (milk, water, etc.) and environmental matrices. Moreover, the validation procedures, necessary to assure methods reliability, are still lacking. In this work, a radiochemical analytical method for the determination of radiostrontium in several solid foodstuffs (meat, seafood, dairy products, wheat and derived products) was optimised and validated, following an in-house validation model, according to reference legislation. Good analytical performances were obtained. Method specificity and linearity were ascertained together with measurement uncertainty (equal to 16.0 %). The minimal detectable activity was equal to 8.0 mBq kg −1 , while the mean repeatability (CV%) and recovery values were equal to 14.5 and 90.5 %, respectively. A test on a reference material was also effected, confirming method reliability for 90 Sr quantifications in solid foodstuffs.