A method for the determination of trace amounts of La, Y and Eu, based on the formation of volatile chelates between rare earth elements and 1-phenyl-3-methyl-4-benzoyl-pyrazolone [5] (PMBP) in a graphite furnace, is described. PMBP was used as a chemical modifier for the volatilization of La, Y and Eu from the electrothermal vaporizer into the ICP. The factors affecting the chelating reaction between La, Y and Eu and PMBP were studied in detail, and the vaporization behavior of the chelates formed in the graphite furnace was also investigated. It was found that the presence of an excess of PMBP was necessary to prevent the thermal decomposition of the chelates during the volatilization and transportation processes. Under the optimized conditions, the limits of detection for La, Y and Eu are 8.0, 1.0 and 0.9 ng ml-1, respectively, and the relative standard deviations range from 3.3% (La) to 4.0% (Y). The linear ranges of the calibration graphs span three orders of magnitude. The method was applied to the analysis of an environmental reference material and the results obtained were in good agreement with the reference values.

The vaporization behavior of silicon and three refractory trace elements (Al, Ti and Y) were studied in the presence and absence of a PTFE emulsion as fluorinating reagent and applying an electrothermal ICP-AES coupled system.It was found that during a 60 s ashing step at 700℃ about 90% of 100mg of Si3N4 can be decomposed and evaporated without considerable losses of the trace elements investigated. Calibration could be carried out by the standard addition method and the calibration curve method applying spiked slurries and aqueous standard solutions with peak height intensity measurements, respectively. The detection limits varied from 0.11 mg g−1 (Al) to 0.09mg g−1 (Ti) with RSD 1.9-4.2%.

A method has been developed for the determination of trace impurities in silicon nitride (Si3N4) powders by fluorination assisted electrothermal vaporization (ETV)/ICP-AES using the slurry sampling technique. Polytetrafluoroethylene (PTFE) emulsion as a fluorinating reagent not only effectively destroys the skeleton of Si3N4, but also carries out selective volatilization between the impurity elements (Cu, Cr) and the matrix (Si). The experimental parameters influencing fluorination reactions were optimized. The detection limits for Cu and Cr are 1.05ng/mL (Cu) and 1.58ng/mL (Cr), the RSDs are in the range of 1.9-4.2%. The proposed method has been applied to the determination of Cu and Cr in Si3N4 ceramic powders. The analytical results were compared with those obtained by independent methods.

Fluorination assisted electrothermal vaporization (ETV) was employed as sample introduction technique for the direct determination of trace amounts of impurities in titanium dioxide solid powder by inductively coupled plasma atomic emission spectrometry (ICP-AES). A polytetrafluoroethylene (PTFE) emulsion is used as a fluorination reagent to promote the vaporization of impurity elements in TiO2 powder from the graphite tube; the vaporization behavior of matrix element (Ti) and analyte (Cr, Cu, Fe and V) were studied. Under the selected conditions, about 100mg solid sample (10ml of 1%m/v TiO2 slurry) was pipetted into furnace, a pre-volatilization of the matrix could be performed by an ashing time of 70 s at 800℃ to eliminate the matrix effect, and then the analytes were vaporized into plasma at the vaporizing temperature of 2600℃. Calibration was performed using the standard addition method. The accuracy was checked by comparison of the results with solution fluorination assisted ETV-ICP-AES and pneumatic nebulization (PN)-ICP-AES based on the wet-chemical decomposition. Limits of detection between 0.07μg g−1 (Cr) and 0.2μg g−1 (V) were achieved. © 2000 Elsevier Science B.V. All rights reserved.

hermal vaporization inductively coupled plasma atomic emission spectrometry (ETV-ICP-AES) was employed for the direct determination of trace impurities in silicon carbide ceramic powders. The vaporization behaviors of silicon and five trace elements (Al, Cr, Cu, Fe and V) were studied in the presence and absence of polytetrafluoroethylene (PTFE) as fluorinating reagent. It was found that, during a 60 s ashing step at 800℃, about 97% of 100 mg of SiC can be decomposed and evaporated without considerable losses of the trace elements investigated. Calibration was performed using the standard addition method and the calibration curve method, applying spiked slurries and aqueous standard solutions, respectively. The accuracy was checked by comparison of the results with those obtained by solution fluorination assisted ETV-ICP-AES and pneumatic nebulization (PN)-ICP-AES involving wet chemical decomposition of the sample. Detection limits between 0.3μg g-1 (Al) and 0.08μg g-1 (Cu) were achieved. The precision, expressed as the relative standard deviation (RSD), was between 6.0% (for 18.2μg g-1 of Cr) and 2.8% (for 177μg g-1 of Fe).