We describe the analytical performance of a hybrid material composed of SiO 2 , Al 2 O 3 and TiO 2 . It was prepared by a sol-gel process and can act as an adsorbent in the continuous-flow enrichment of copper. A minicolumn was packed with the material, copper ions are adsorbed at pH 9.13, then eluted with 1.0 mol L −1 nitric acid, and determined by FAAS. The material was characterized by infrared spectroscopy, scanning electron and energy dispersive spectroscopy, energy dispersive X-ray fluorescence analysis, powder Xray diffraction, and specific surface area analysis. No significant interference was observed for most ions in up to copper/ interferent ratios of 1:100 and of 1:500 in case of Ca(II), Ba (II), and Mg(II). The breakthrough capacity is 1.4 mg g −1 under dynamic conditions. The limits of detection and of quantification are 0.50 and 1.4 μg L −1 , respectively, and the calibration plot is linear in the range from 5.0 to 245.0 μg L −1 (r00.999). The relative standard deviation is 3.20 (for n07 and at a Cu(II) concentration of 10 μg L −1 ). The method was applied to the determination of trace copper ions in water, vegetable and alcohol fuel samples.

In the present study, a flow injection system using dual mini-columns, SiO(2)/Al(2)O(3)/TiO(2) and silica gel functionalized with [3-(2-aminoethylamino)propyl] trimethoxysilane (SiO(2)/AAPTMS) for the sequential preconcentration of Cr(III) and Cr(VI), respectively, from water samples with FAAS detection was proposed. A two-level full factorial design (2(4)) and desirability function were employed for the optimization of variables related to the system performance. The detection limits of 0.66 and 0.27 μg L(-1) for Cr(III) and Cr(IV), respectively, were obtained under the optimized preconcentration conditions (flow rate of 7.0 mL min(-1)), pH 5.0, buffer concentration (acetate buffer) of 0.01 mol L(-1), and eluent (2.5 mol L(-1) HCl) flow rate of 5.0 mL min(-1). The other parameters including preconcentration factor (PF), consumptive index (CI), and concentration efficiency (CE) were found to be 17.62/32.98, 1.13/0.6 mL, and 6.2/11.54 min(-1) for Cr(III)/Cr(VI), respectively. The developed method was applied to the Cr(III) and Cr(VI) determination in water samples [tap, lake and mineral water, artificial saliva and parenteral solutions (physiological serum, water for injection, and glucose physiological solution)]. The method accuracy was checked by the analysis of standard reference materials (trace elements in water).

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