Flow injection on-line sorption preconcentration of trace amounts of copper and manganese in a knotted reactor precoated with 1-phenyl-3-methyl-4-benzoylpyrazol-5-one coupled with electrothermal atomic absorption spectrometry

Abstract

A new scheme was developed for the flow injection on-line sorption preconcentration of trace elements in a knotted reactor (KR) precoated with the chelating reagent 1-phenyl-3-methyl-4-benzoylypyrazol-5-one. It offers several advantages in comparison with the conventional preconcentration scheme involving on-line merging of the sample and chelating reagent solution: higher sensitivity owing to the more favourable conditions of analyte preconcentration on the ‘immobilized’ reagent, better optimization of the separated processes of reagent sorption on the KR and analyte preconcentration, no analyte losses due to adsorption of chelate complexes on the tubing outside the KR and no need of a prefill step between samples of different analyte concentration. The performance characteristics of the method for copper and manganese, respectively, are as follows: detection limits (3σ), 5.7 and 5.0 ng l ^–1 ; minimum detectable masses, 0.014 and 0.013 ng; precision (RSD), 2.4% for 0.1 µg l ^–1 copper and 1.9% for 0.1 µg l ^–1 manganese; enhancement factors, 33.6 and 20.8 for a 30 s preconcentration time; and concentration efficiencies, 12.1 and 7.5. The sampling frequency was 21.6 h ^–1 . The accuracy of the method was demonstrated by the analysis of certified reference materials.