On-line Preconcentration and Determination of Zn in Natural Water Samples Employing a Styrene-Divinylbenzene Functionalized Resin and Flame Atomic Absorption Spectrometry

In this work, flame atomic absorption spectrometry (FAAS) was used as a detector for the determination of zinc in natural water samples with a flow-injection system coupled to solid-phase extraction (SPE). In order to promote the on-line preconcentration of zinc from samples a minicolumn packed with 35 mg of a styrene-divinylbenzene resin functionalized with (S)-2-[hydroxy-bis(4-vinylphenyl)methyl]pyrrolidine-1-carboxylic acid ethyl esther was utilized. The system operation was based on Zn(II) ion retention at pH 9.5 ± 0.5 in such a minicolumn with analyte elution, at the back flush mode, with 1 mol L-1 HCl directly to the FAAS nebulizer. The influence of the chemical (sample pH, buffer concentration, HCl eluent concentration and effect of the ionic strength) and flow (sample and eluent flow rates and preconcentration time) parameters that could affect the performance of the system were investigated as well as the possible interferents. At the optimum conditions, for 2 min of preconcentration time (9.9 ml of sample volume), the developed methodology presented a detection limit of 1.1 µg L-1, a RSD of 3.5% at 10 µg L-1 and an analytical throughput of 24 h-1. Whereas, for 4 min of the preconcentration time (19.8 ml of sample volume) a detection limit of 0.98 µg L-1, a RSD of 6.5% at 5 µg L-1 and a sampling frequency of 13 h-1 are reported.