Glow discharge mass spectrometry instrumentation

In the last decade or two, the advent of new instrumentation directed at elemental analysis has provided fertile new ground for expanded use of isotope dilution. Glow discharge mass spectrometry is in many ways the modem replacement for spark source and has similar impediments to ready application of isotope dilution. A recent report of Barshick et al. describes assaying lead in oil residues using the technique [21]. The obstacles spark source and glow discharge mass spectrometry both present to ready use of isotope dilution make it unlikely that widespread application of the technique will occur in conjunction with them. 

Figure 7 Radio frequency glow discharge mass spectrometry (rf GD-MS) source designs employed on a VG GloQuad instrument for the analysis of a, Pin-type samples. (From Ref. 28.) b, Flat samples. (From Ref. 29.)...

Fig. 120. Glow discharge mass spectrometry. A Sector field based instrument (a) glow discharge source (b) magnetic sector field (c) electrostatic energy analyzer (d) Daly detector (e) ...

Another particular but interesting observation of new rare earth ionic species has been made in the ion sources of elemental analytic MS instruments. Rare earth argide ions, MAr, have been detected in plasma MS (ICP-MS, LA-ICP-MS, and glow discharge mass spectrometry (GD-MS)), with the... 

Jakubowski, N., Feldmann, I., and Stuewer, D. (1997). Grimm-type glow discharge ion source for operation with a high resolution inductively coupled plasma mass spectrometry instrument./. Ana/. At. Spectrom. 12(2), 151. 

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. 

Today, as a direct solid-state analytical technique, dc GDMS is more frequently applied for multi-element determination of trace contaminants, mostly of high purity metallic bulk samples (or of alloys) especially for process control in industrial laboratories. The capability of GDMS in comparison to GD-OES (glow discharge optical emission spectrometry) is demonstrated in a round robin test for trace and ultratrace analysis on pure copper materials.17 All mass spectrometric laboratories in this round robin test used the GDMS VG 9000 as the instrument, but for several... 

Atomic mass spectrometry has been around for many years, but the introduction of the inductively coupled plasma in the 1970s and its subsequent development for mass spectrometry led to its successful commercialization by several instrument companies. Today inductively coupled plasma mass spectrometry (ICP-MS) is a widely used technique for the simultaneous determination of more than 70 elements in a few minutes. Some other sources, such as the glow discharge, are also used for atomic mass spectrometry. Because the ICP predominates, however, the discussion here focuses on ICP-MS. 

As in the sources used in optical atomic spectrometry a considerable ionization takes place, they are also of use as ion sources for mass spectrometry. Although an overall treatment of instrumentation for mass spectrometry is given in other textbooks [68], the most common types of mass spectrometers will be briefly outlined here. In particular, the new types of elemental mass spectrometry sources have to be considered, namely the glow discharges and the inductively and eventually the microwave plasmas. In contrast with classical high voltage spark mass spectrometry (for a review see Ref. [69]) or thermionic mass spectrometry (see e.g. Ref. [70]), the plasma sources mentioned are operated at a pressure which is considerably... 

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