Flow injection on-line preconcentration of trace zinc (II) ions in water samples using a synthesized 8-hydroxyquinoline functionalized amberlite XAD-2 resin and determination by flame atomic absorption spectrometry

Abstract

An on-line flow injection preconcentration method for trace amounts of zinc at ppb (parts per billion) levels in real water samples was developed using flow injection flame atomic absorption spectrometry (FI-FAAS). A new chelating resin of 8-hydroxy-quinoline functionalized Amberlite XAD-2 was synthesized, characterized, and used for complexation of zinc. Optimization of the flow injection variables was done for the determination and quantitative preconcentration of zinc. The sample acidity was adjusted to pH 8.0 for the effective retention of zinc ions on the resin. The chelating resin can be reused for 90-100 cycles of sorption-desorption without any significant change in its activity. The adsorbed zinc ions were eluted with 0.3 mol L-1 HNO3. The calibration graph obtained was found to be linear over the concentration range of 0 to 80 μg L-1. An enhancement factor of 137-fold for a sample volume of 15 mL was obtained by using the time-based technique. The detection limit for the preconcentration method was found to be 0.33 μg L-1. The precision (RSD %) for 10 replicate determinations at 40 and 80 μg L-1 concentration was 2.5 and 2.1%, respectively. The sample throughput was 30 h-1 for a 5-mL sample. The effect of common interfering ions present in water samples on the selectivity of the resin towards zinc was also studied and the tolerance limit for them is reported. To test the accuracy of the developed on-line FI-FAAS procedure, standard reference material (SRM) NIST 1643e Trace Elements in Water was analyzed. Further-more, the developed procedure was successfully tested for spiked water samples.