The Phosphine Depression in Flame Atomic Spectrometry

Abstract

The presence of PH3 in C2H2 can cause serious depressions of analyte atomic signals in air/C2H2 and N2O/C2H2 flames. In elements other than those in group 1a and 1b, a refractory metal-phosphorus-oxygen compound is formed during analyte desolvation and appears to slow the vaporization process. Data is presented describing the magnitude of the PH3 depression for elements routinely determined in these flames. The effects of the PH3 depression for these elements are compared to H3PO4 depressions, and the success of using chelating agents (EDTA) to reduce the depression is explored. Deviations from mathematical models describing the PH3 effect are discussed, and the possibility of incomplete PH, combustion occurring in the flames is explored.