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).

Fluorination-assisted electrothermal vaporization (ETV)-inductively coupled plasma-atomic emission spectrometry (ICPAES) for the direct determination of trace amounts of refractory impurity elements in silicon carbide ceramic powders using slurry sampling has been developed. Investigation indicated that a polytetrafluoroethylene (PTFE) emulsion is a useful fluorinating reagent for the destruction of silicon carbide and simultaneous vaporization of the refractory impurities like B, Mo, Ti, and Zr. The vaporization behaviors of the analytes in slurry and solution were comparatively investigated in the presence of PTFE. The fluorinating vaporization processes and the influence factors for this method have been also studied in detail. The experimental results indicated that 80mg silicon carbide (10ml of 0.8% (m/v) slurry) could be destroyed and vaporized completely with 600mg of PTFE under the selected conditions. Calibrationwas performed using the standard addition method with aqueous standard solutions. 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 a wet-chemical decomposition of the sample. Detection limits between 0.5mg g−1 (B) and 0.2mg g−1 (Mo) were achieved. In most cases, the precision expressed as relative standard deviation (R.S.D.) was better than 8%. © 2001 Elsevier Science B.V. All rights reserved.

A new analytical procedure for the direct determination of metal impurities (Cr, Cu, Fe and V) in aluminium oxide ceramic powders by slurry sampling fluorination assisted electrothermal vaporization-inductively coupled plasma-atomic emission spectrometry (ETV-ICPAES) is reported. A polytetrafluoroethylene (PTFE) emulsion was used as a fluorinating reagent to promote the vaporization of impurity elements in aluminium oxide ceramic powders from the graphite tube. A vaporization stage with a long ramp time and a short hold time provided the possibility of temporal analyte-matrix separation. The experimental results indicated that a 10μL1% m/v slurry of aluminium oxide could be destroyed and vaporized completely with 600μg PTFE under the selected conditions. Two aluminium oxide ceramic powder samples were used without any additional pretreatment. Analytical results obtained by using standard addition method with aqueous standard solution were checked by comparison of the results with pneumatic nebulization (PN)-ICP-AES based on the wet-chemical decomposition and analyte-matrix separation. The limits of detection (LODs) between 0.30μg g-1 (Fe ) and 0.08μgg-1 (Cu) were achieved, and, the repeatability of measurements was mainly better than 10%.

Titania microtubules with high specific surface areas and well-developed framework mesopores forming the tubular walls by a surfactant-mediated template in the sol-gel process were fabricated in a laurylamine hydrochloride (LAHC)/tetra-n-butyl-orthotitanate (TBOT) system. The outer diameter and the wall thickness of titania microtubules are 2-8 and 0.2-2μm, respectively. The walls of the microtubules consisted of nanochannels with exceptionally uniform pore size. This technique is a convenient and facile procedure for fabricating hierarchical ordered hollow tubules. The possible mechanism of the formation of the microtubules in the present system was discussed in detail.