Determination of 90Sr in Portuguese foodstuffs

Determination of 90Sr and 210Pb in food samples by liquid scintillation counting after sequential separation with an extraction chromatographic column

90Sr and 210Pb are considered to be key radionuclides in internal exposure resulting from dietary intake, however, the established methods employed for their detection are time-comsuming. A method for the sequential separation of 90Sr and 210Pb using a Sr·spec resin by LSC measurement is developed, which is highly suitable for food safety monitoring as its minimal sample requirements. The sequential separation of Sr and Pb from the sample was using 0.05 mol/L HNO3 and 0.05 mol/L C6H5O7(NH4)3. The chemical recoveries of Sr and Pb measured using ICP-OES were 72-83% and 80-88%, respectively. The minimum detectable activities of 90Sr and 210Pb in the food sample were 36.2 mBq/kg and 28.6 mBq/kg, respectively, obtained from a 0.1 kg fresh sample and 300 min counting time. The method was validated using reference materials and compared with other methods. The feasibility of the developed method for other highly complex food matrices needs further investigation.

Fast and Sensitive Radiochemical Method for Sr-90 Determination in Food and Feed by Chromatographic Extraction and Liquid Scintillation Counting

Strontium-90 (Sr-90) contamination in food is a major public health issue. Several radiochemical methods are available for the determination of Sr-90. However, the application of these procedures is not focused on solid foods, but only on liquid (milk, water, etc.) and environmental matrices, and they were not fully validated. The aims of this work were to establish and validate a fast, sensitive method for the determination of Sr-90 in solid food matrices such as meat and dairy products, seafood, vegetables, and animal feed, using a specific resin for extraction and ultra-low-level liquid scintillation counting for detection. The method was optimised and validated according to relevant legislation. Good analytical performance was obtained, including high specificity and linearity together with low measurement uncertainty (13.1%). The minimal detectable activity was 11 mBq kg−1, and the mean repeatability (CV%) and recovery values were 10.7% and 100.1%, respectively. These parameters assured method applicability for official food safety controls. The method was applied to reference materials and submitted to proficiency test round to confirm its reliability for Sr-90 quantification in solid foodstuffs and feed. The newly established method may be broadly applicable to complex matrices.