Selective precipitation of potassium in seawater samples for improving the sensitivity of plain γ-ray spectrometry

An analytical method is presented to reduce the amount of ⁴⁰K in sea water samples, in order to lower its interference in γ-ray analysis below 1.4 MeV due to the Compton continuum. Sodium tetraphenylborate was used to successfully precipitate ⁴⁰K in the samples. A custom procedure for precipitation of potassium was developed and it was evaluated for its selectivity, reproducibility and efficiency, using conventional analytical techniques such as atomic absorption spectrophotometry and inductively coupled plasma mass spectrometry (ICP-MS). This work has shown that the selective precipitation of potassium with sodium tetraphenylborate has led to a decrease of detection limit of radio nuclides such as ²³⁸U, ²²⁶Ra, ²²⁸Ra, ¹³⁷Cs, ¹³⁴Cs, ¹³³I, ¹³⁴I, ⁶⁰Co in γ-analysis. In particular, the detection limit for nuclides with emissions in the energy window energy below 1400 keV is improved by almost one order of magnitude