Supercritical fluid extraction of cadmium as Cd-oxine complex from human hair -: Determination by square wave anodic or adsorptive stripping voltammetry

A method is presented for the extraction of cadmium as the Cd(OX)2 complex with methanol-modified supercritical CO2. In a first step, aliquots of Cd2+ solutions were spiked onto filter paper and air-dried, and the filter paper with cadmium, oxine and methanol was placed in a 10 ml stainless steel extraction vessel. A study was made of extraction as a function of pressure (6.9-24.1 MPa), oven temperature (40-200degreesC), restrictor temperature (20-100 degreesC), presence of modifier (1.0-4.0 n-d), and static extraction time (10-50 min). Quantitative extractions of cadmium were achieved when the experiments were carried out at 17.2MPa, 80-120degreesC oven temperature, 60degreesC restrictor temperature, 2.0-3.0 ml of methanol, 30 min static extraction, and 5 min in dynamic mode. An aliquot of the extract was placed in an electroanalytical cell that contained a supporting electrolyte, and cadmium was quantified by square wave stripping voltammetry. The calibration graphs using cadmium solutions in the presence of 0.1 M of oxine were linear over a 5.0-120.0 mug1(-1) range. The detection limits using anodic stripping voltammetry or adsorptive stripping voltammetry were 1.5 and 1.4 mug1(-1) of cadmium, respectively. The efficiency of the extraction was evaluated using certified reference human hair. The procedure was then applied to cigarette samples and to hair of cigarette smokers and non-smokers. Cadmium concentration ranges were 0.06-0.57 mug g(-1) (average 0.25 +/- 0.18 mug g(-1)) for smokers and 0.02-0.26 mug g(-1) (average 0.11 +/- 0.07 mug g(-1)) for non-smokers. (C) 2003 Elsevier B.V. All rights reserved.