Application of a field flow preconcentration system with a minicolumn packed with amberlite XAD-4/1-(2-pyridylazo)-2-naphthol and a flow injection-flame atomic absorption spectrometric system for lead determination in sea water

A field flow preconcentration technique involving a minicolumn containing Amberlite XAD-4 impregnated with the complexing agent 1-(2-pyridylazo)-2-naphthol was used to preconcentrate lead from seawater. Elution of retained lead on the mini-columns was performed by a flow-injection-flame atomic absorption spectrometric system. Factorial designs have been used to optimise the field flow preconcentration system and the flow injection elution process. Factors such as sample pH, sample flow-rate, eluent concentration and volume (hydrochloric acid), elution flow-rate and minicolumn diameter were considered. The results suggest that the sample flow-rate and the eluent volume are statistically significant factors. The detection limit (3sigma) of the procedure was 5 ng/L for a sample volume of 1000 mL. The precision (expressed as relative standard deviation) for eleven independent determinations reached values of 4.0-3.1% in lead solutions of 50-200 ng/L. This procedure has been successfully applied to the determination of lead in seawater from Galicia (Spain).