A rapid method for analysis of non-equilibrated 90Sr/90Y in infant formula.

A rapid analytical method for quantifying 90Sr in infant formula prior to secular equilibrium is presented. The approach is dependent on the use of two separations of 90Sr from 90Y, with the first providing an 90Y ingrowth start point and the second providing an 90Y ingrowth end point. Data were obtained at activity concentrations of approximately 6 Bq/kg and 160 Bq/kg, the latter of which is representative of the US Food and Drug Administration (FDA) Derived Intervention Levels (DIL). Experiments were designed to collect data from ingrowth periods ranging from 16 h to 2 weeks. Activities obtained with a separation interval as low as 16 h ranged from 92.7 to 109.4% of the known value. When 90Y ingrowth was allowed to occur for 24 h or longer, the activities ranged from 93.2 to 106.2% of the known value and the precision of this group improved from 5.2 to 3.1%. The limit of quantification (LOQ) was 0.5 Bq/kg using 250 g sample portions.