Vesicular Hydride Generation–In Situ Preconcentration–Electrothermal Atomic Absorption Spectrometry Determination of Sub-parts-per-billion Levels of Cadmium

Abstract

Studies to increase the sensitivity of cadmium determination by atomic absorption spectrometry using continuous hydride generation from a vesicular medium within situ preconcentration in a graphite tube are described. Parameters influencing the efficiency of the continuous generation and transport of cadmium hydride are studied in detail using a Pd-coated graphite platform for in situ preconcentration. Continuous stirring of the sample solutions enhanced, approximately ten-fold, the determination of cadmium. The detection limit (LOD) observed for Cd was 5 ng l–1 when preconcentrating 1.4 ml of sample. Improved LOD can be achieved by preconcentrating larger volumes of sample solution, limited only by a maximum deposition of 0.2 ng Cd on to the platform. The observed relative standard deviation for ten replicate analyses of 0.14 ng of total Cd (1.4 ml of a 100 ng l–1 solution) was excellent (±1.1%). The use of W- and Zr-coated platforms and uncoated graphite tubes for preconcentrating Cd in situ was compared with the Pd-coated platform procedure described. The proposed method has been applied successfully to the determination of ng l–1 levels of this toxic metal in river water and tea infusions.