The determination of sodium in water at ultra-trace concentrations by flameless atomic-absorption spectrophotometry

Abstract

A flameless atomic-absorption technique has been developed for the determination of sodium in water at levels of 0.1 µg kg^–1 and lower. A practical limit of detection of 0.011 µg kg^–1 has been determined and the method was shown to be unaffected by the presence of ammonia at concentrations of up to 8 mg kg^–1. No anion interference has been found for the anions chloride, sulphate and hydroxide. In laboratory tests, a comparison of the atomic-absorption results with those obtained by using a sodium-selective glass electrode indicated a positive bias in the electrode results. This bias was, however, found to be reduced during power-station plant trials when the glass electrode was presented with a low-sodium water over a period of days. Thus the sluggish response of the electrode system may have contributed to the observed bias in the laboratory tests.