On-line preconcentration/determination of cadmium in drinking water on activated carbon using 8-hydroxyquinoline in a flow injection system coupled to an inductively coupled plasma optical emission spectrometer

An on-line cadmium preconcentration and determination system implemented with inductively coupled plasma optical emission spectrometry associated to flow injection was studied. Cadmium was retained as Cd–8-hydroxyquinoline complex at pH 10.0. The cadmium complex was removed from the conical minicolumn packed with activated carbon with 20% (v/v) nitric acid. An enrichment factor of 80-fold for a sample volume of 50 ml was obtained. The detection limit (DL) value for the preconcentration of 50 ml of sample was 18 ng l−1. The relative standard deviation was 2.5%, calculated from the peak heights obtained. The calibration graph using the preconcentration system for cadmium was linear with a correlation coefficient of 0.9995 at levels near the DLs up to at least 100 ng ml−1. The method was successfully applied to the determination of total cadmium in drinking water samples.