Determination of cadmium and lead by chemical vapor generation atomic absorption spectrometry.

摘要

The development of methods for the determination of cadmium and lead at the ultra-trace concentration level has been the object of great attention during the past 20 years. The reason for this interest is their high toxicity even at these low levels, given the fact that once exposure has occurred the elements are accumulated in the body. Several instrumental techniques have been applied to the determination of cadmium and lead in biological and environmental samples, such as urine, blood, hair, foodstuffs, natural and domestic waters, etc. The variation in the complexity of these matrices is quite large, so that measuring the contents of cadmium and lead is a difficult operation because of the concentration of interfering species coexisting in the samples with a low concentration of the analytes.; The application of chemical vapor generation procedures to this task offers the possibility to transfer the analyte to a medium free of interferences in a concentration that facilitates a determination by means of spectrometric techniques.; In the work described in this dissertation, flow injection methods for the determination of cadmium and lead were devised according to two approaches: the generation of the vapor species with simultaneous transport and detection in an atomization T-cell placed above the burner of a Perkin Elmer 3100 atomic absorption spectrometer; and the generation of the vapor species for their preconcentration on the iridium-coated interior surface of a graphite furnace atomizer, whose temperature was thereafter raised for atomization and detection in two electrothermal atomic absorption spectrometers: a Perkin Elmer 4100ZL, and a Perkin Elmer SIMAA6000. For both approaches, the limits of detection obtained were in the low ng l--1 range.; Special attention was given to: (a) the testing of several different designs of gas-liquid separators to maximize the efficiency in the transfer of the analytes from the sample to the atomizer while minimizing transfer of liquid, (b) corroborate the enhanced efficiency reported for several additives such as surfactants and transition metals, and (c) improve the limits of detection in the determination of lead by minimizing contamination of the analytical blank.