Determination of trace rare earth elements by inductively coupled plasma optical emission spectrometry after preconcentration with immobilized nanometer titanium dioxide

Nanometer titanium dioxide immobilized on silica gel (immobilized nanometer TiO2) was prepared by the sol-gel method and characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The adsorptive potential of immobilized nanometer TiO2 for rare earth elements (REEs) was assessed in this work. The REE ions can be quantitatively retained by immobilized nanometer TiO2 at a pH range of 6 - 9, and 0.5 mol L-1 HNO3 was sufficient for complete elution. A method has been developed for the determination of trace REEs based on preconcentration with a microcolumn packed with immobilized nanometer TiO2 and determination by inductively coupled plasma optical emission spectrometry (ICP-OES). The material showed relatively high chemical stability towards the action of acidic solutions. The packed microcolumn used in proposed procedure did not show any over pressure or swelling and can be used up to at least 20 adsorption-elution cycles without decrease in the performance. The optimum experimental parameters for preconcentration of REEs, such as pH of the sample, sample flow rate and volume, elution solution and interfering ions, have been investigated. The detection limits for REEs was between 3 and 57 ng L-1, and the relative standard deviations ( RSDs) for the determination of REEs at 10 ng mL(-1) level were found to be less than 6% when processing 100 mL sample solution. The method has been successfully applied to the determination of trace REEs in some environmental samples.