Synthesis and characterization of a novel mesoporous silica functionalized with [1,5 bis(di-2-pyridyl)methylene thiocarbohydrazide] and its application as enrichment sorbent for determination of antimony by FI-HG-ETAAS

A simple, sensitive, low-cost and rapid flow injection (FI) on-line sorption preconcentration/hydride generation system has been synchronously coupled to an electrothermal atomic absorption spectrometer (ETAAS) for the determination of trace amounts of Sb in aqueous environmental samples (river and sea water samples). The system is based on retention of the analyte onto a micro-column filled with a novel mesoporous silica functionalised with [1,5 bis(di-2-pyridyl) methylene] thiocarbohydrazide placed in the injection valve of the FI manifold. The adsorption capacity of the resin for Sb was found to be 160.8 mu mol g(-1). Chemicals and flow variables affecting the continuous preconcentration of antimony, the direct generation of antimony hydride and the final determination of this element by ETAAS were evaluated. The optimized operating conditions selected were: sample pH 5.0, sample flow rate 2.5 ml min(-1), eluent flow rate 5.4 ml min(-1), eluent 2.0% thiourea in 4.0% nitric acid. Under the optimum conditions, the calibration graph obtained was linear over the range 0.025-2.5 mu g L-1. At a sample frequency of 20 h(-1) and 120 s preconcentration time, the enrichment factor was 22. The detection limit of the method (3o) was 1 ng L-1 for a 5.0 mL sample volume and the precision was 0.9% (RSD) for 11 replicate determinations at 1.0 mu g L-1 Sb. The preconcentration factor and detection limit can be improved by increasing the preconcentration time, which can be increased at least up to 5 min. The accuracy of the proposed method was demonstrated by analyzing two certified reference materials and by determining the analyte content in spiked environmental water samples. The results obtained using this method were in good agreement with the certified values of the standard reference materials and the recoveries for the spiked river and sea water samples were 91.3-109.9%. (C) 2014 Elsevier B.V. All rights reserved.