Investigations of interferences in graphite furnace atomic absorption spectrometry using a dual-cavity platform. Part 2. Influence of sodium chloride and nickel chloride on the atomisation of lead

Abstract

The interferences from sodium and nickel chlorides on the determination of lead which occur in the absence of a modifier are not due to gas-phase interactions. Some lead chloride is lost in the form of gaseous molecules at temperatures above 500 °C. In the presence of nickel chloride, lead is lost primarily by co-volatilisation with the hydrogen chloride gas, which is generated by the decomposition of the salt. Expulsion of the analyte by matrix vapours was found to be a source of interference with both of the chlorides investigated. Nitric acid had no influence on the interference from sodium chloride but reduced the interference from nickel chloride. The stabilising effect found on the addition of both nitric acid and nickel chloride was due to nickel only. Various interactions between the gas phase and the condensed phase were observed when analyte and interferent were separated on the dual-cavity platform. The determination of lead in the presence of sodium or nickel chlorides was free from interferences when ammonium phosphate-magnesium nitrate was added as a modifier.