Although there are numerous cations and anions in real samples generally, the interference effects of a matrix consisting of one cation and one anion on the atomization of an element in graphite furnace atomic absorption spectrometry (GFAAS) have been investigated. Therefore, it would be more realistic to investigate the interference of a matrix containing more than one cation and anion. In this study, the simultaneous interference effects of sodium, magnesium, sulphate and chlorine, which are the most common and abundant ions in many samples, e.g. sea water, on the atomization of manganese in GFAAS were studied. As a first step, the individual interferences of some possible salts consisting of simple combinations of the ions studied such as sodium chloride, magnesium chloride, sodium sulphate and magnesium sulphate, were investigated. It was found that in the presence of these four ions and in their wide concentration range, sodium chloride and magnesium sulphate are the major salts formed after the drying step which were supported by X-ray diffraction (XRD) studies. Sodium chloride causes a significant depressive effect at low pyrolysis temperatures. The interference of sodium chloride originates from expulsion of the analyte with matrix and gas phase reaction between manganese and chloride ions during atomization. Magnesium sulphate does not cause any depression and in fact higher pyrolysis temperatures compared to matrix-free manganese can be applied without loss of any analyte. The depressive effect of sodium chloride on manganese markedly decreased in the presence of magnesium sulphate due to its protecting effect. The mutual interaction mechanism of these two salts and their effects on manganese have been discussed. (C) 1999 Elsevier Science B.V. All rights reserved.