A method of glow discharge atomic emission spectroscopy (GD-AES) is described for the determination of rare earth elements (REEs) after separation and preconcentration by micro-column packed with immobilized 1-phenyl-3-methyl-4-benzoyl-5-pyrazone (PMBP) on icrocrystalline naphthalene. The graphite electrode with solution residue on its surface was used as a cathode. Various factors (the form of cathode, working condition) influencing the determination of the analytes were studied in detail. Under the experimental conditions selected, the detection limits for the determination of La, Nd, Eu, Dy and Y are 0.24, 0.32, 0.01, 0.07 and 0.06mg/mL, respectively, with relative standard deviations (RSDs) in the range of 5-10%. The method was applied to determine La, Nd, Eu, Dy and Y in geological samples, and the analytical results are in good agreement with the reference values.

In this paper, several fluoride chemical modifiers have been tested for electrothermal vaporization-inductively coupled plasma atomic emission spectrometry (ETV-ICP-AES) determination of different volatile elements, such as refractory element Ti, medium volatile element Ni and easy volatile element Pb. Reagents tested include polytetrafluoroethylene (PTFE), NH4F, NaF and CuF2•2H2O. The best overall results are obtained using 6% PTFE added to sample. Under the compromise operating conditions, the detection limits of analytes are in the range of 0.8-59μgml 1 and the calibration curves are linear for over three orders of magnitude. The direct determination of Ti, Ni and Pb in GBW 08505 tea leaves reference sample is shown as an example of PTFE chemical modification.

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 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.