Flow injection on-line minicolumn preconcentration and determination of trace copper ions using an alumina/titanium oxide grafted silica matrix and FAAS

We describe the analytical performance of a hybrid material composed of SiO2, Al2O3 and TiO2. 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 X-ray 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 mu g L-1, respectively, and the calibration plot is linear in the range from 5.0 to 245.0 mu g L-1 (r = 0.999). The relative standard deviation is 3.20 (for n = 7 and at a Cu(II) concentration of 10 mu g L-1). The method was applied to the determination of trace copper ions in water, vegetable and alcohol fuel samples.