Ultratrace determination of cadmium by atomic absorption spectrometry using hydride generation with in situ preconcentration in a palladium-coated graphite atomizer

Abstract

A very sensitive ETAAS method, with in situ trapping of the metal, is described for ultratrace determinations of Cd in liquid solutions. It is based on volatile Cd HG from a vesicular solution with subsequent trapping of the metal in a graphite platform coated with Pd. This Pd coating, on a pyrolytic graphite L'vov platform, acts as the atomizer. Sodium tetrahydroborate (III) in a vesicular medium of didodecyldimethylammonium bromide is used to generate Cd hydride from the sample solution. This volatile species is trapped by the Pd coating, pre-heated at 150 °C, the preconcentrated Cd then atomized at 1600 °C and the transient AAS signal measured. Detection limits (DL) observed are in the ng l–1 range (e.g., using a 1.4 ml Cd sample volume for preconcentration the DL was 60 ng l–1). Higher preconcentrations up to a maximum of 1.4 ng of total Cd deposited are possible with the proposed methodology. The RSD for ten replicate analyses of 1.4 ml of 500 ng l–1 Cd solution (0.7 ng of total Cd) was 1.7%. The combination of vesicles-mediated HG with the ease of decomposition of Cd hydride on the Pd coating at 150 °C, provides a convenient Cd preconcentration method for enhancing the sensitivity of direct determinations of Cd by conventional ETAAS or by HGAAS.