Effects of Alkali and Alkaline Earth Metal Chlorides on the Atomization of Lead and Chromium in Graphite Furnace Atomic Absorption Spectrometry

Abstract

Potassium chloride, calcium chloride, sodium chloride and magnesium chloride cause many different types of interference in the determination of lead and chromium by graphite furnace atomic absorption spectrometry. Simultaneous volatilization of the analyte and the interferent from different, but close, points in the tube are very helpful in the explanation of interference mechanisms. The kind of interference that affects the sensitivity of the determination depends on the thermal behavior of the matrix before and during atomization of the elements. If chloride vapor is formed by decomposition of the matrix before or during atomization of the analyte elements, the formation of a metal chloride in the gas phase may be responsible for decreasing in the sensitivity. If, on the other hand, the matrix is present as a solid or liquid while the elements atomize, the occlusion of the analyte in the bulk of the matrix and the loss by a carrier-type mechanism or a slower transfer of heat to the analyte delaying the atomization cause some changes in the sensitivity. Expulsion of analyte vapors by expanding matrix gases was not effective due to the low heating-rate of the system used.