Electrothermal atomic absorption spectrometric determination of lead, cadmium, copper and zinc in high-salt content samples after simultaneous separation on polyethylene powder impregnated with 1-(2-pyridylazo)-2-naphthol: application to the analysis of hemodialysis fluids

A simultaneous separation and preconcentration of lead, cadmium, zinc and c opper from high-salt content matrices for subsequent electrothermal atomic absorption spectrometric determination was developed. The metals were preco ncentrated on a micro-column filled with polyethylene powder impregnated wi th the complexing agent 1-(2-pyridylazo)-2-naphthol. The determinations, wi thout the interference of the saline matrix, were carried out after metals elution with a small volume of an ethanolic solution of nitric acid. The sa line matrices were sodium, potassium, magnesium and calcium chlorides, sodi um acetate and bicarbonate, which constitute concentrates for hemodialysis. The immobilisation capacity of the complexing agent is about 2.5 mu mol pe r gram of polyethylene and the column capacity with respect to each metal i s about 0.75 mu mol per gram resin for copper, cadmium and zinc and 0.25 mu mol per gram for lead. For the optimisation of the procedure, effects of s ample flow rate and pH, eluent composition and concentration, and the influ ence of salts on the complexation of the metals were investigated. The prop osed method was characterised by a precision of about 95% (n = 3) and recov eries from spiked samples of the salts were 81-112%. All results were in ag reement with those obtained by anodic stripping voltammetry, the technique used for comparison. The method was applied to the analysis of saline conce ntrates for hemodialysis, where the investigated metals were found in conce ntrations between 3.1 mu g l(-1) for cadmium and 90.5 mu g l(-1) for zinc.