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

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.