Modifier effects in the determination of arsenic, antimony and bismuth by electrothermal atomic absorption spectrometry

The effect of palladium, mixed palladium-magnesium and magnesium modifiers on the determination of arsenic, antimony and bismuth was tested. It was found that palladium modifier works correctly only in nitric acid solution. If the sample solution contains hydrochloric acid then palladium becomes a strong interferent and causes significant losses of the analyte. For arsenic and antimony, but not for bismuth, this shortcoming may be eliminated by use of mixed palladium-magnesium or magnesium modifier. Magnesium modifier was found to be superior to the mixed modifier since it is able to eliminate also the negative effects of perchloric acid and of the iron group elements. It is, however, completely ineffective in relation to bismuth when used individually or in a mixture with palladium. Palladium may be used as a modifier for the determination of antimony and bismuth in hydrochloric acid solution only when it is preliminarily reduced to the metal form. The mechanism of the modifier activity is discussed.