VESICULAR HYDRIDE GENERATION - IN-SITU PRECONCENTRATION - ELECTROTHERMAL ATOMIC-ABSORPTION SPECTROMETRY DETERMINATION OF SUB-PARTS-PER-BILLION LEVELS OF CADMIUM

Studies to increase the sensitivity of cadmium determination by atomic absorption spectrometry using continuous hydride generation from a ve sicular medium with in situ preconcentration in a graphite tube are de scribed. Parameters influencing the efficiency of the continuous gener ation and transport of cadmium hydride are studied in detail using a P d-coated graphite platform for in situ preconcentration. Continuous st irring of the sample solutions enhanced, approximately ten-fold, the d etermination of cadmium. The detection limit (LOD) observed for Cd was 5 ng l(-1) when preconcentrating 1.4 ml of sample, Improved LOD can b e achieved by preconcentrating larger volumes of sample solution, limi ted only by a maximum deposition of 0.2 ng Cd on to the platform, The observed relative standard deviation for ten replicate analyses of 0.1 4 ng of total Cd (1.4 ml of a 100 ng l(-1) solution) was excellent (+/ - 1.1%). The use of Wand Zr-coated platforms and uncoated graphite tub es for preconcentrating Cd in situ was compared with the Pd-coated pla tform procedure described. The proposed method has been applied succes sfully to the determination of ng l(-1) levels of this toxic metal in river water and tea infusions.