Direct analysis of Al2O3 powders by total reflection X-ray fluorescence spectrometry
A direct analysis procedure for the determination of trace impurities of Ca, V, Cr, Mn, Fe, Ni, Cu, Zn and Ga in Al2O3 ceramic powders by total reflection X-ray fluorescence spectrometry (TXRF) is described. The powders were analysed in the form of slurries containing 1–10 mg mL−1 of powder. The use of the procedure in the case of powders with differing grain size and for different slurry concentrations was investigated. Three different quantification possibilities were compared, namely the use of Al as a matrix component, the use of Fe as a trace element contained in the sample or of Co added in concentrations of 200 μg g−1 as internal standard. The homogeneity of elemental distributions in sample layers deposited on the TXRF quartz carriers by evaporating 5 μL of the 10 mg mL−1 slurries was studied by scanning the 4- to 5-mm-diameter spots of two samples by synchrotron radiation TXRF at Hasylab. For powders with differing graininess but mainly finer than about a few 10 μm, no systematic influence of the grain size on the accuracy of the determinations of Ca, V, Fe, Ni, Cu and Zn could be observed. The measurement precision, however, seemed to be limited by inhomogeneous distributions of the trace elements in the samples as testified by the synchrotron radiation TXRF scans. Detection limits of the developed TXRF procedure for Ca, V, Cr, Mn, Fe, Ni, Cu, Zn and Ga were found to be in the 0.3–7 μg g−1 range and were shown to increase slightly with the grain size of the samples. Quantification using Al (matrix) as internal standard led to systematically higher values out of the accuracy required, whereas the other two approaches in all cases led to reliable results.
Microwave Digestion of Thermoluminescent Aluminium-Oxide Powders and Determination of Trace Impurities by Inductively Coupled Plasma Optical Emission Spectroscopy
Abstract. Five commercial and three laboratory prepared thermoluminescent aluminium-oxide powders as well as three reference samples were digested by a microwave digestion system and the impurities were determined by ICP-OES. The physico-chemical properties of the different samples were found to influence highly the decomposition efficiency. Optimized decompositi on parameters were determined for the samples with different physico-chemical properties (phase composition, grain size). The detection limits of the impurities of interest are presented, the analysis results for the aluminium- oxide dosimetric samples and the standards are given as well for Be, Ca, Ce, Cu, Fe, Cd, Mg, Mo, Na, Ni, Ti and Zn in the < 2–400 μg/g range.
Optimization of the electrothermal vaporization conditions for inductively coupled plasma excitation spectrometry: Selective volatilization versus covolatilization approaches
A new version of the outlet port of a graphite furnace electrothermal vaporizer (upward streaming system) is described, in which the hot sample vapour is mixed with an auxiliary carrier argon stream of ambient temperature. The operation procedures using carrier volatilization of organic liquids as gas phase additives are also outlined. The selective volatilization and transport efficiency for As, Cd, Hg, Pb, Sb, Se and Zn could be increased by applying sodium thiosulfate as chemical modifier to solution samples with controlled nitric acid content. On the other hand, a near simultaneous vaporization of 16 elements using chlorination with CCl4 vapour at 2100° C could be performed for a multielement analysis. By wetting the auxiliary carrier argon stream, the linearity of the analytical curves was improved (except for chromium), when applying multielement standards. Linear analytical curves could also be obtained in the presence of alkali and alkaline earth metal matrices in multielement standards using halocarbon assisted electrothermal vaporization sample introduction.