COMPARISON OF SODIUM-CHLORIDE AND MAGNESIUM-CHLORIDE INTERFERENCES IN CONTINUUM SOURCE ATOMIC-ABSORPTION SPECTROMETRY WITH WALL, PLATFORM AND PROBE ELECTROTHERMAL ATOMIZATION

Various masses between 10 and 500-mu-g of NaCl or MgCl2 were added to 1 ng of Cr, Cu and Mn, 2 ng of Cd and Pb and 4 ng of Co, Mo, Ni and V to study the interferences encountered when wall, platform and probe atomization are applied in continuum source electrothermal atomic absorption spectrometry. No char step was used and a compromise atomization temperature of 2700-degrees-C was selected for simultaneous multi-element measurements. No great difference was observed in the analyte signal recovery values obtained with the three atomization modes when NaCl was the interferent. However, with MgCl2, greater interferences were observed with wall atomization. Overall, probe atomization proved as good as, if not better than platform atomization for the elements considered. With both procedures, freedom from NaCl or MgCl2 interferences was achieved at chloride salt:analyte mole ratios of 1 x 10(3)-1 x 10(5). Although it was not possible to make a definitive assessment of the procedures responsible for the interferences observed, there was some evidence that vapour-phase chemical effects are more important for MgCl2 than for NaCl, occlusion of Cd, Mn and Pb occurs in NaCl and expulsion of Co, Cr, Cu, Mn and Ni occurs due to co-vaporization with NaCl.