Direct determination of ultra-trace sodium in reactor secondary coolant waters and other waters by electrolyte cathode discharge atomic emission spectrometry

Abstract

A simple, rapid and sensitive method has been described for direct determination of ultra-trace sodium in reactor secondary coolant waters and other waters by electrolyte cathode discharge atomic emission spectrometer (ELCAD-AES). This method obviates the need of any sample digestion except simple dilution followed by analysis of these waters. Direct analysis of the samples for their very low level sodium is found to be feasible by ELCAD-AES with 3% v/v formic acid without going for chemical processing/treatment like evaporation of matrix or separation and pre-concentration of sodium. The 3% v/v formic acid improves the detection limit of sodium which is found to be 0.5 ng mL−1. Repeatability of the method was found to be 8% whereas the accuracy was between 10 and 20% at ultra-trace levels. As the certified reference materials for these waters are not available, the method is validated with the corresponding results determined by graphite furnace atomic absorption spectrometer (GFAAS). The proposed method is found to be useful for direct determination of trace and ultra-trace sodium in reactor coolant waters, high purity waters and in tap and ground waters. Therefore, ELCAD-AES can be an alternative analytical technique to check ultra-trace levels of sodium and quality of the coolant waters for nuclear industries.