Establishment of a Sr-90 determination method in powdered milk using extraction chromatography and liquid scintillation counting

The Fukushima accident in 2011 raised concerns about spreading radioactive contaminants, particularly Strontium-90 (Sr-90) due to its high environmental mobility and potential bioaccumulation in the food chain. This research developed an analytical method for determining Sr-90 activity concentration in powdered milk, combining extraction chromatography with Liquid Scintillation Counting (LSC). Strontium was separated using a commercially available Sr-resin from Eichrom, and beta activity was measured with an LSC. Method performance was assessed through chemical recovery using Atomic Absorption Spectroscopy (AAS) and method recovery evaluation using LSC. The method was tested on five commercial powdered milk samples imported from Japan to Indonesia to evaluate its applicability. The result of the chemical recovery value was a maximum of 49.60%. The efficiency value of the LSC instrument was 58.08%, and the method recovery in this study was 82.96%. Sample E exhibited the highest Sr-90 activity concentration at 0.823 Bq/kg, while sample B had the lowest concentration at 0.6589 Bq/kg. Compared with the IAEA guidance level for Sr-90 content in milk (100 Bq/kg), the five powdered milk samples analysed were still within safety limits for consumption. Although the influence of quenching in LSC was acknowledged qualitatively, no quantitative correction was performed. The efficiency calibration against a reference standard solution partially compensates for matrix-induced quenching, and future work will establish quench correction curves to improve measurement accuracy and compliance with international protocols. This research is expected to presents a new method that is more effective and efficient in determining Sr-90 activity concentration in powdered milk samples than the conventional method.