THE INTERFERENCE EFFECT OF MORE THAN ONE SALT IN GRAPHITE-FURNACE ATOMIC-ABSORPTION SPECTROMETRY .1. EFFECT OF MAGNESIUM-CHLORIDE SODIUM-CHLORIDE MIXTURE ON MANGANESE

The simultaneous interference effects of sodium chloride and magnesium chloride on the atomization of manganese in a graphite furnace were i nvestigated. For this purpose, the individual interference mechanisms of each salt were also studied. It was found that the interference of sodium chloride originates from expulsion of the analyte with matrix a nd gas phase reaction between manganese and chlorine during the atomiz ation step. In the presence of magnesium chloride, interferences depen d on the pyrolysis temperature. If low pyrolysis temperatures are appl ied, expulsion and gas phase reaction in the atomization step are very likely. At elevated temperatures, MgCl2 is converted to MgO, which do es not cause expulsion or gas phase reaction in the atomization step, although some loss of manganese occurs owing to the volatilization of manganese chloride formed in the pyrolysis step. If sodium chloride an d magnesium chloride are present simultaneously, interferences are red uced at elevated pyrolysis temperatures. Obviously, the magnesium oxid e generated by the hydrolysis of magnesium chloride acts as a modifier and partially protects the analyte, but some losses cannot be complet ely eliminated because of the interference due to sodium chloride and the volatilization of manganese chloride. (C) 1997 Elsevier Science B. V.