Investigation of the effect of some inorganic salts on the determination of tin in graphite furnace atomic absorption spectrometry

The interference mechanisms of sulfate and chloride salts of sodium, potassium and nickel on tin in graphite furnace atomic absorption spectrometry were studied by using a dual cavity platform. For this purpose, different sets of experiments such as pyrolysis curves for mixed and separated solutions of analyte and interferent, background signals in the pyrolysis stage, and atomization from tube wall and platform were investigated. It was found that sodium and potassium chlorides and sulfates cause gas phase reactions between the analyte and decomposition products of the interferent and/or expulsion of analyte vapor from the furnace together with rapidly expanding matrix gases in the atomization step. The interference effects of nickel chloride and sulfate depend on the pyrolysis temperature. At low pyrolysis temperatures interferents do not change their chemical form, and cause gas phase and/or expulsion interferences in the atomization step. At elevated temperatures both salts are converted to NiO which does not cause interferences any more, and even acts as a modifier for tin. When the sample is atomized from the wall, interferences were always more pronounced than for atomization from the platform because of the more extensive gas-phase and/or expulsion interferences.