Rapid Quantification of Radioactive Strontium-90 in Fresh Foods via Online Solid-Phase Extraction–Inductively Coupled Plasma–Dynamic Reaction Cell-Mass Spectrometry and Its Comparative Evaluation with Conventional Radiometry

This paper describes a rapid quantification method for radioactive strontium (⁹⁰Sr) in fresh foods (perishable foods) and has been comparatively evaluated with the common classical radiometric quantification method. Inductively coupled plasma–dynamic reaction cell-mass spectrometry with online solid-phase extraction (cascade-ICP–MS) rapidly determines ⁹⁰Sr in a pure water-based sample. Despite its advantages, its application to fresh foods (perishable foods) has not yet been reported; however, the analytical potential of this method for fresh foods must be evaluated. In this study, ⁹⁰Sr was determined in 12 fresh foods via improved cascade-ICP–MS (Icas-ICP–MS). Addition and recovery tests were demonstrated using real samples of grape, apple, peach, Japanese pear, rice, buckwheat, soybean, spinach, shiitake mushroom, grass, sea squirt, and flounder. With a decomposed solution of Japanese pear, the measurement value coincided with the amount of spiked ⁹⁰Sr. The reproducibility of the measurements was represented by relative standard deviations of 14.2 and 5.0% for spiked amounts of 20 and 200 Bq/kg, respectively (n = 10), and the recovery rates were 93.7 ± 7.1%. In this case, the limit of detection (LOD) was 2.2 Bq/kg (=0.43 pg/kg). These results were compared with the data obtained using a common classical radiometric quantification method (nitrate precipitation-low background gas flow counter (LBC) method) in the same samples. Both the methods showed equivalent performances with regard to reproducibility, precision, and LODs but different analysis times. Icas-ICP–MS required ∼22 min for analysis, whereas the nitrate precipitation-LBC method required 20 days, confirming that Icas-ICP–MS is the suitable method for analyzing ⁹⁰Sr in fresh foods.