A simple and selective method of flow injection (FI) using a micro-column packed with chelating resin YPA4 as solid phase extractant was developed for the preconcentration and separation of trace amount of noble metals, Au (Ⅲ), Ag (Ⅰ), Pd (Ⅱ) and Pt (Ⅳ), followed by ICP-AES determination. In HNO3 media, the chelating resin was selective towards Au(Ⅲ), Ag (Ⅰ), Pd (Ⅱ) and Pt (Ⅳ), and the analysed ions were readily desorbed quantitatively with 5ml of 2.5%m/v thiourea. Effects of acidity, sample flow rate and concentration, elution solution and interfering ions on the recovery of the analytes were systematically investigated. Under optimum conditions, the adsorption capacities of YPA4 for Au (Ⅲ), Ag (Ⅰ), Pd (Ⅱ) and Pt (Ⅳ) were 67.2, 43.1, 64.8 and 27.6mg per gram of resin in HNO3 media, respectively. It was found that YPA4 could be used for more than eight runs in HNO3 media without loss of capacity. The proposed method was used for the determination of trace noble metals in geological and environmental samples, and theanalytical results obtained were in good agreement with the recommended 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.

Anovel method for inductively coupled plasma atomic emission spectrometry (ICP-AES) determination of trace amounts of Pt (Ⅱ), Pd (Ⅱ) and Rh (Ⅲ), based on gaseous compounds introduction into the plasma as their diethyldithiocarbamate complexes by electrothermal vaporization (ETV), was developed. At the temperature of 1100℃, the trace amounts of Pt, Pd and Rh were vaporized into plasma. The factors affecting the formation of the chelates and their vaporization behaviors, such as ashing temperature and time, vaporization temperature and time, pH and the concentration of chelating reagents were studied in detail. Under the optimized conditions, the limits of detection (LODs) (3σ) of Pt, Pd and Rh for tested solutions were 5.4, 1.4 and 0.8μgml−1, and for actual sample (auto-catalyst NIST SRM 2557) were 0.27, 0.07 and 0.04g g−1, respectively. The relative standard deviations (RSDs) for Pt, Pd and Rh were 1.4, 2.6 and 2.4% (CPt=0.5 gml−1, CPd, Rh=0.25 gml−1, n=7), respectively. The linear ranges of calibration graphs for Pt, Pd and Rh cover three orders of magnitude. Compared with conventional electrothermal vaporization technique, using the reagent of diethyldithiocarbamate as chemical modifier could not only enhance the analytical sensitivities, but also reduce the vaporization temperature. By combination with a separation/preconcentration step, the proposed method had been successfully applied to the analysis of the artificial seawater, tap water and urine with recoveries ranging from 91 to 106%. The two certified reference material meager platinpalladium ore GBW 07293 and auto-catalyst NIST SRM 2557 was also analyzed for validation, and the determined values obtained were in good agreement with the certified values.

A method of electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS) for the determination of trace lanthanides and yttrium in soil samples with a polytetrafluorethylene (PTFE) emulsion as chemical modifier to promote the vaporization of the analytes from the graphite furnace was developed in this paper. The analytical characteristics, spectral interference and matrix effect of the analytical method were evaluated and critically compared with those of pneumatic nebulization inductively coupled plasma mass spectrometry (PN-ICP-MS). Under the optimized operation conditions, the relative detection limits of lanthanides (La-Lu) and yttrium for ETV-ICP-MS and PN-ICP-MS were 0.4-20ngl−1 and 1.0-21ngl−1, respectively, the absolute detection limits for ETV-ICP-MS were 4-200 fg, which were improved by 1-2 orders of magnitude compared with PN-ICP-MS. While the analytical precision of ETV-ICP-MS is worse than that of PN-ICP-MS, with the R. S. D. S (%) of 4.1-10% for the former and 2.9-7.8% for the latter. Regarding to the matrix effect, both conventional method and stepwise dilution method were employed to observe the effect of matrix and the very similar results were obtained. It was found that the highest tolerance concentration of the matrix is 1000mgl−1 and 800mgl−1 for ETV-ICP-MS and PN-ICP-MS, respectively. To assess the accuracy, the proposed method was applied to the determination of trace lanthanides and yttrium in three different soil standard reference materials and one soil sample, and the determined values are in good agreement with the certified values or reference 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.