A method was developed to determine refractory elements by inductively coupled plasma-atomic emission spectrometry (ICP-AES) with sample introduction by electrothermal vaporization (ETV). A slurry of polytetrafluoroethylene (PTFE) was used as fluorinating reagent to promote the vaporization of refractory elements from a graphite furnace and to avoid the formation of difficult volatile carbides. With this treatment the refractory elements can be efficiently vaporized, and subsequently introduced into the plasma. The detection limits of this method were in the picogram to sub-nanogram range and superior to those obtained with conventional nebulization systems, and were comparable with those obtained with similar ETV-ICP-AES techniques. The analyte vaporization and transport process was systematically explored, and the corresponding vaporization and transport mechanisms of refractory elements in this system have been proposed. The matrix effects and sample particle size effects in fluorination assisted ETV-ICP-AES were significantly reduced. Therefore, an effective method for lowering the matrix interferences has been proposed.

A new method of single-drop microextraction combined with low-temperature electrothermal vaporization (LTETV)-ICPMS was proposed for the determination of trace Be, Co, Pd, and Cd with benzoylacetone (BZA) as both extractant and chemical modifier. Several factors that influence the microextraction efficiency, such as sample flow rate, microdrop volume, and extraction time, were investigated and the optimized microextraction conditions were established. Be, Co, Pd, and Cd in the postextraction organic phase were directly determined by LTETV-ICPMS with the use of BZA as chemical modifier. The chemical modification of BZA in LTETV-ICPMS was studied, and the factors affecting the formation of chelates and vaporization/ transportation of chelates were investigated. Under the optimized conditions, the detection limits of the method were 0.12, 0.99, 1.5, and 0.27pg/mL for Be, Co, Pd, and Cd, and the relative standard deviations for 0.1ng/mL Be, Co, Pd, and Cd were 16, 14, 14, and 11%, respectively. After 10min of extraction, the enrichment factors were 160 (Be), 125 (Co), 40 (Pd), and 180 (Cd). The proposed method was applied to the determination of trace Be, Co, Pd, and Cd in biological reference materials, and the determined values were in good greement with the certified values.

A new method for the determination of free La3+ and La organic complexes in solution using a nanometer-sized titanium dioxide as solid-phase extractant and fluorinationassisted electrothermal vaporization (FETV)-ICP-AES as sensitive detector has been developed. The effect of pH on the adsorption characteristics of La3+ and La complexes of citric acid, 2-hydroxyisobutyric acid (HIBA), and humic acid on nanometer-sized TiO2 was investigated and optimized. On the basis of the difference in volatility between fluoride of analyte (lanthanum) and the fluoride of matrix (titanium), an in-situ removal of the adsorbent matrix (TiO2) from a graphite furnace was realized. Therefore, the free La3+ and adsorbed La complexes on nanometersized titanium dioxide could be determined respectively by FETV-ICP-AES without any other chemical pretreatment. The proposed method was applied for the determination of free ion (La3+) and La complexes in synthetic solutions and soil extracts with satisfactory results.

Nanometre-sized alumina was chemically modified with c-mercaptopropyltrimethoxysilane (c-MPTMS). The modified nanometer-sized alumina was characterized by X-ray power diffusion (XRD), X-ray photoelectron energy spectrometer (XPS) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) before it was used as solid phase adsorption material for the inductively coupled plasma mass spectrometry (ICP-MS) determination of trace amounts of Hg, Cu, Au and Pd. The effects of pH, sample flow rate and volume, elution solution and interfering ions on the recovery of the analytes have been investigated. Under the optimized conditions, the adsorption capacity of modified nanometer-sized Al2O3 was found as 10.4, 16.3, 15.3, and 17.4 mg g21 for Hg, Cu, Au and Pd, respectively. The limits of detection were as low as 0.066 and 0.49 ng L21 for Cu and Hg with a concentration factor of 100 times, and 0.46 and 0.26 ng L21 for Au and Pd with a concentration factor of 200 times. The developed method has been applied to the determination of trace Hg and Cu in biological and environmental certified materials and Au and Pd in geological certified materials, and the determined values were in a good agreement with the certified values.

An in-situ electrothermal fluorination-assisted matrix removal method was developed with PTFE as chemical modifier, and trace-levels of Cr, Co and V in ZrO2 powder were determined. The solid samples were directly introduced into the graphite furnace in the form of a slurry, where the Zr matrix reacted with the active carbon fluoride formed by electrothermal decomposition of PTFE during the pyrolysis stage. Without loss of analytes, the Zr matrix was completely vaporized and removed by the carrier gas. As a result, the matrix interference, which was serious without the modifier, was effectively suppressed, and the chemical attack of the excess of the Zr matrix on the graphite tube was also minimized. The standard additions calibration and the aqueous standard calibration were compared and similar results were obtained. The removal of matrix, the background absorption, the chemical modification of PTFE and the temperature-time program of the graphite furnace were investigated and optimized. The proposed method was applied to the direct determination of trace amounts of Cr, Co and V in ZrO2 powder with aqueous calibration and the results obtained were in good agreement with those obtained by pneumatic nebulization ICP-AES after digestion and separation of the matrix Zr with PMBP extraction. The detection limits of Cr, Co and V were 0.20, 0.32 and 3.7mg g21, respectively.