Rapid determination of Cs and precise Cs/Cs atomic ratio in environmental samples by single-column chromatography coupled to triple-quadrupole inductively coupled plasma-mass spectrometry

For source identification, measurement of ¹³⁵Cs/¹³⁷Cs atomic ratio not only provides information apart from the detection of ¹³⁴Cs and ¹³⁷Cs, but it can also overcome the application limit that measurement of the ¹³⁴Cs/¹³⁷Cs ratio has due to the short half-life of ¹³⁴Cs (2.06 y). With the recent advancement of ICP-MS, it is necessary to improve the corresponding separation method for rapid and precise ¹³⁵Cs/¹³⁷Cs atomic ratio analysis. A novel separation and purification technique was developed for the new generation of triple-quadrupole inductively coupled plasma-mass spectrometry (ICP-MS/MS). The simple chemical separation, incorporating ammonium molybdophosphate selective adsorption of Cs and subsequent single cation-exchange chromatography, removes the majority of isobaric and polyatomic interference elements. Subsequently, the ICP-MS/MS removes residual interference elements and eliminates the peak tailing effect of stable ¹³³Cs, at m/z 134, 135, and 137. The developed analytical method was successfully applied to measure ¹³⁵Cs/¹³⁷Cs atomic ratios and ¹³⁵Cs activities in environmental samples (soil and sediment) for radiocesium source identification.