On-line complexation of zinc with 5-Br-PADAP and preconcentration using a knotted reactor for inductively coupled plasma atomic emission spectrometric determination in river water samples

An on-line zinc preconcentration and determination system implemented with inductively coupled plasma atomic emission spectrometry (ICP-AES) associate d with flow injection (FI) was studied. The zinc was retained as zinc-2-(5- bromo-2-pyridylazo)-5-diethylaminophenol (Zn-(5-Br-PADAP)) complex at pH 9. 2. The zinc complex was removed from the knotted reactor (KR) with 30% v/v nitric acid. An enrichment factor of 42 was obtained for the KR system with respect to ICP-AES using pneumatic nebulization. The detection limit for t he preconcentration of 10 mL of aqueous solution was 0.09 mu g/L. The preci sion for 10 replicate determinations at the 5 mu g/L Zn level was 2.3% rela tive standard deviation (RSD), calculated with the peak heights obtained. T he calibration graph using the preconcentration system for zinc was linear with a correlation coefficient of 0.9997 at levels near the detection limit s up to at least 100 mu g/L. The method was succesfully applied to the dete rmination of zinc in river water samples.