Rapid and sensitive determination of radiocesium (Cs-135, Cs-137) in the presence of excess barium by electrothermal vaporization-inductively coupled plasma-mass spectrometry (ETV-ICP-MS) with potassium thiocyanate as modifier

An electrothermal vaporization-inductively coupled plasma-mass spectrometric (ETV-ICP-MS) method based on selective volatilization of cesium with KSCN as modifier has been developed for determination of radiocesium, i.e. ¹³⁵Cs and ¹³⁷Cs, in the presence of isobaric barium. A 10000 times excess of barium, which was volatilized at a temperature of 1100?°C, resulted only in a 1% signal increase in the signal of mass 135 amu. The recommended concentration of KSCN is 0.3 mM, and pretreatment and volatilization temperatures are 400?°C and 1100?°C, respectively. A ramp time of 1 s is recommeded for the volatilization step. The achieved limit of detection for ¹³⁵Cs is 0.2 pg/mL (10 μBq/mL) and 4 fg (0.2 μBq) absolute for a sample volume of 20 μL. This means a limit of detection for ¹³⁷Cs of 0.2 pg/mL (0.6 Bq/mL) and of 4 fg (0.01 Bq) absolute. Signal variations of ¹³⁵Cs and ¹³⁷Cs, respectively, in spiked samples with various matrices were investigated.