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

Abstract

This paper describes a rapid quantification method for radioactive strontium ( 90 Sr) 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 90 Sr 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, 90 Sr 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 90 Sr. 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 90 Sr in fresh foods.

Development of Online Dilution System for Quantification of 90Sr Using Automatic Solid-phase Extraction Inductively Coupled Plasma Mass Spectrometry

“…[5][6][7] Previous reports have demonstrated the applications of the cascade ICP-MS system for 90 Sr quantification in groundwater, rainwater, and solid samples. [5][6][7][8][9] However, the introduction of a large amount of the matrix material into the ICP-MS system, due to multiple measurements of the samples containing the matrix material, causes considerable loss of sensitivity and necessitates the cleaning of the inner parts such as cones and DRC. This probrem, which has been actually faced, should be easily observed in analysis with several grams of marine products because the allowable limit of salt concentration in the samples is <1000 mg/L.…”

“…[ 90 Sr] T / Bq L -1 Counting rate in the main-flow line ± standard deviation / cps Previous method [7][8][9][10] Proposed e. Concordance ratio (%) was given using the following equation: (measured value/spiked value) ×100…”

A Part Per Trillion Isotope Ratio Analysis of 90Sr/88Sr using Energy-Filtered Thermal ionization mass spectrometry

“…8 Nuclear accidents are another source of anthropogenic 90 Sr emissions into the environment, resulting in local fallout with high activities. 90 Sr was one of the major radioactive nuclides released in the Chernobyl [9][10][11] and Fukushima [12][13][14][15] nuclear reactor accidents. When taken up by animals, including humans, 90 Sr has the potential to cause long-term internal exposure.…”

“…19 Conventionally, radiometric methods using solid/liquid scintillators or gas ionization detectors were used to detect 90 Sr in various environmental samples. 5,[12][13][14][15] The radiometric method is fundamentally a counting experiment of the decaying atoms. Because 90 Sr has a half-life of 28.79 years, 24 the fraction of the decaying atom is signi cantly small: approximately 1.3 × 10 9 atoms of 90 Sr corresponds to 1 Bq (or decay per minutes) of activity.…”

“…ICP-MS's major source of noise signals is 90 Zr. 2,24,25 In environmental samples, the ratio between minor 90 Sr and more abundant stable isotopes of Sr or isobaric isotope 90 Zr is extremely high (i.e., at least nine orders of magnitude 15 ). ICP ion source e ciently ionizes 90 Zr, which remains in the sample solution in trace amounts even after Sr extraction chemistry.…”