The determination of 21 elements was investigated in the presence of the palladium nitrate-magnesium nitrate (Pd-Mg) mixed modifier. Significantly higher pyrolysis temperatures could be used for the majority of elements compared with previously recommended modifiers, making possible an efficient removal of concomitants prior to the atomization of analyte elements. A 10 pg amount (1 g I-') of NaCl had no influence on the determination of all of the elements investigated and most of the analyte elements were not affected even by a ten times higher concentration. The concentration of potassium sulfate, which had no influence on the determination, was lower for most of the elements. The tolerance towards NaCl and K2S04 increased significantly for a number of elements when the pyrolysis temperature was lowered by 200-300 "C and the pyrolysis time was increased. For most of the elements investigated the characteristic mass values were comparable to, or better than published data. For some elements, however, such as bismuth, lead and tellurium, the characteristic mass was significantly higher. This resulted from the high stabilizing power of the Pd-Mg modifier, which necessitated higher atomization temperatures for these elements for which diffusional losses were more pronounced. The advantages and limitations of the Pd-Mg modifier are discussed.

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A sensitive method has been developed for the determination of mercury (0.2-1.2 p.p.m.1 using phenanthroline and eosin in an aqueous medium. The reaction occurs at pH 4.5. Various metal ion interferences have been evaluated.

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