Glow discharge direct current

Table 8.60 shows the main features of GD-MS. Whereas d.c.-GD-MS is commercial, r.f.-GD-MS lacks commercial instruments, which limits spreading. Glow discharge is much more reliable than spark-source mass spectrometry. GD-MS is particularly valuable for studies of alloys and semiconductors [371], Detection limits at the ppb level have been reported for GD-MS [372], as compared to typical values of 10 ppm for GD-AES. The quantitative performance of GD-MS is uncertain. It appears that 5 % quantitative results are possible, assuming suitable standards are available for direct comparison of ion currents [373], Sources of error that may contribute to quantitative uncertainty include sample inhomogeneity, spectral interferences, matrix differences and changes in discharge conditions. 

A GD mass spectrometer from Thermo Fisher Scientific with a direct current (dc) glow discharge ion source based on the mass spectrometric arrangement of the Element (Element GD) has been available on the analytical market since 2005 for sensitive multi-element analysis of trace impurities in conducting samples. The experimental arrangement of the dc GD ion source (Grimm type) and... 

Figure 5.27 Schematic diagram of direct current (dc) glow discharge mass spectrometer (VC 9000).

Figure 5.28 Direct current glow discharge ion source a) schematic, b) photograph of Element CD (Thermo Fisher Scientific, Bremen, German), Reproduced by permission of Thermo Fisher Scientific,...

M. Vazquez Pelaez, J. M. Costa-Fernandez, R. Pereiro, N. Bordel and A. Sanz-Medel, Quantitative depth profile analysis by direct current glow discharge time of flight mass spectrometry, J. Anal. At. Spectrom., 18,2003, 864-871. 

Direct Current and Radio Frequency Glow Discharge Operation... 

A plant for this purpose comprises a vacuum chamber with ancillary equipment. The articles to be plated are mounted on a water-cooled cathode and, following evacuation of the chamber and filling with argon to a pressure of 0.002 Torr, direct current from a supply in the range 2000 to 5000 V is applied—to give a glow discharge in the area of the cathode. The article or articles mounted there thus are cleaned by ionic bombardment. Next, the evaporation source is excited, and the atoms of source material are deposited on the work pieces. 

ECR electron cyclotron resonance plasma RF radio frequency plasma DCGD direct current glow discharge plasma DHMy dimethylhydrazine SFs stacking faults, PL photoluminescence. 

The direct introduction of atomic vapour into the AAS flame can also be seen as an equipment variation [148, 152], Here, the evaporation of the steel samples can be carried out with the help of the glow-discharge lamp [148] or an aerosol generator with a low current d.c.-arc discharge [152]. Another example is the combination of gas chromatography and AAS [92], where AAS is used as an element detector. 

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