Determination of 236U in environmental samples by single extraction chromatography coupled to triple-quadrupole inductively coupled plasma-mass spectrometry

•A simple 236U/238U analytical method has been developed.•The separation required just one DGA column chromatography.•236U/238U atom ratios in soil were measured by ICP-MS/MS.•236U/238U atom ratios of (1.50-13.5) × 10−8 were observed in Japanese samples.•236U activities of (2.25-14.1) × 10−2 mBq kg−1 were found in Japanese samples.

In order to measure trace 236U and 236U/238U in environmental samples with a high matrix effect, a novel and simple method was developed that makes the digestion and purification procedures compatible with advanced triple-quadrupole inductively coupled plasma-mass spectrometry. A total dissolution of sample with HF + HNO3 + HClO4 was followed by chromatographic separation with a single resin column containing normal type DGA resin (N,N,N′,N'-tetra-n-octyldiglycolamide) as the extractant system. The analytical accuracy and precision of 236U/238U ratios, measured as 236U16O+/238U16O+, were examined by using the reference materials IAEA-135, IAEA-385, IAEA-447, and JSAC 0471. The low method detection limit (3.50 × 10−6 Bq kg−1) makes it possible to perform routine monitoring of environmental 236U due to global fallout combined with the Fukushima Daiichi Nuclear Power Plant accident fallout (>10−5 Bq kg−1). Finally, the developed method was successfully applied to measure 236U/238U ratios and 236U activities in soil samples contaminated by the accident. The low 236U/238U atom ratios ((1.50-13.5) × 10−8) and 236U activities ((2.25-14.1) × 10−2 mBq kg−1) indicate 236U contamination was mainly derived from global fallout in the examined samples.

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