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Calibration of two commercially available glow discharge double focusing mass spectrometers, the VG 9000 and Element GD, is described using synthetic pin standards pressed from solution doped copper and zinc matrices. A special pressing die was developed for this purpose and optimal results were obtained with the highest possible pressures, i.e., 95 kN·cm- 2. This calibration approach permits the determination of trace element mass fractions down to µg·kg- 1 with small uncertainties and additionally provides traceability of the GD-MS results in the most direct manner to the SI (International System of Units). Results were validated by concurrent measurements of a number of compact copper and zinc certified reference materials. The impact of the sample pin cross-section (circular or square) was investigated with the use of a new pin-sample holder system for the Element GD. The pin-sample holder was designed by the manufacturer for pin-samples having circular cross-section; however, samples with square pin cross-section were also shown to provide acceptable results. Relative Sensitivity Factors for some 50 analytes in copper (VG 9000, Element GD) and zinc matrices (VG 9000) are presented. The field of applicability of GD-MS may be considerably extended via analysis of pin geometry samples based on their ease of preparation, especially with respect to the accuracy and traceability of the results and the enhanced number of analytes which can be reliably calibrated using such samples.
Synthetic pressed metal powder standards doped with standard solutions were used for the calibration of both commercially available high resolution GD-MS instruments Element GD and VG 9000 for zinc matrix. Different quantification procedures (IBR, Standard RSF, matrix matched RSF from the calibration with CRMs and use of doped synthetic standards) are compared using zinc matrix as an example, whereas the calibration with doped pellets turned out to be the best quantification technique for high-purity materials. The applicability of the Standard RSF concept is scrutinised. In this context, RSF values for several Matrices (Co, Cu, Fe, In and Zn) are reported additionally.
The hollow cathode (HC) effect was investigated in non-cooled 15 mm deep drilled flat metallic analytical samples that were easy to prepare. The deep cavity used ("complete HC" in contrast to "recessed HC" with 2-3 mm deep cavity) intensified the HC effect notably and therefore distinctly improved the detection power of the common GD-OES with planar cathodes. A signal enhancement of up to a factor of 150, not reported earlier, in comparison with flat conventional samples was achieved. A better separation of the analytical lines from spectral interferences was observed when the HC assembly was applied. Additionally, an effect of strongly enhanced intensities of atomic lines and somewhat decreased intensities of ionic lines was detected in the case of HC in comparison to usual planar cathodes. The investigations were carried out with samples of copper, steel and zinc matrices using both the same and individually optimised glow discharge (GD) electrical parameters.