Errors in atomic absorption spectrophotometric determination of Pb, Zn, Ni and Co in geologic materials

Abstract

Errors in atomic absorption spectrophotometric determinations of Pb, Zn, Ni and Co may occur due to the presence of Fe, Al, Ca, Mg, Na and K in the sample solution. At low concentrations of trace element in solution (i.e., up to about 1 p.p.m.) and low concentrations of major elements (up to about 4,000 p.p.m. total cations), the main source of interference is enhancement due to background absorption; this may be corrected by the hydrogen continuum or by use of a non-absorbing wavelength. At higher concentrations of trace element the enhancement due to molecular absorption is partly or completely nullified through suppression caused by major element interference. Similarly, at higher concentrations of major elements, suppression occurs which is probably a function of atomizer efficiency. In these situations, correction for total molecular absorption results in a residual negative error. The errors in determination of Pb, Zn, Ni and Co in geological materials are often ignored in exploration geochemistry work. This restriction on the accuracy of the analytical data is becoming more important with the increasing use of exploration methods based on rock analyses. The errors may be minimized by ensuring that the concentration of both trace element and major element in solution is too low to cause significant suppression effects. Under these circumstances, reasonable results should be obtained through correction for background absorption.