Glow Discharge Sources

4 Clow Discharge Optical Emission Spectroscopy (CD-OESj 223 

Besides the conventional Grimm-type dc source, which has dominated the GD-OES scene for approximately 30 years, other discharge sources are well known. Among those are various boosted sources which use either an additional electrode to achieve a secondary discharge, or a magnetic field or microwave power to enhance the efficiency of excitation, and thus analytical capability none of these sources has, however, yet been applied to surface or depth-profile analysis. 

The introduction of rfpowered sources has extended the capability of GD-OES to non-conductors, and several rf sources of different design have become commercially available. This is of the greatest importance for surface and depth-profile analysis, because there exists a multitude of technically and industrially important non-conductive coating materials (e. g. painted coatings and glasses) which are extremely difficult to analyze by any other technique. 

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Vieth and Huneke have recendy presented a thorough discussion of GDMS quantitation, including the measurement of relative GDMS sensitivity factors and a modeling of glow-discharge source processes to enable semiempirical estimates of... 

To maintain reproducible excitation conditions in the glow discharge source, the working conditions (e. g. argon pressure, dc-current or rf-power) are carefully controlled. 

Glow discharge source (GDMS) Laser ion source (LIMS) Secondary ion source (SIMS) Sputtered neutral source (SNMS) Thermal ionization source (TIMS) Inductively coupled plasma ion source (ICP-MS)... 

Figure 7 Schematic diagram of a coaxial cathode glow discharge source.

Figure 9 Schematic diagram of a Grimm-type glow discharge source. (From Ref. 29.)...

Glow Discharge Sources. Glow discharge (GD) ion sources and some of their applications using different mass analyzers have been discussed in earlier chapters of this volume. Virtually all work that couples these sources to FT-ICR mass analyzers has involved dc discharges (see Chapter 2 for further discussion of the types of GD sources). 

Hang, W Harrison, W. W. Time-of-Flight Mass Spectrometry for a Glow Discharge Source. Presentation 1089 at Pittcon 97, Atlanta, GA, March, 1997. 

Schematic diagram of a glow discharge source with sputtering at the cathode surface and ionization in the discharge.

Hang, W., Yan, X.M., Wayne, D.M. et al. (1999) Glow discharge source interfacing to mass analyzers Theoretical and practical considerations. Anal. Chem., 71 (15), 3231-7. 

Devices for solid sample treatment prior to introduction into atomic spectrometers electrothermal devices and glow-discharge sources... 

Fig. 8.9. Scheme of a dc glow-discharge source and its associated components. (Reproduced with permission of the American Chemical Society.)... 

Glow-discharge sources operate in inert environments and are thus free from atmospheric contaminants ... 

Marcus et al. [234] used a glow-discharge source with direct injection of particles for special samples such as airborne particulates [234]. This novel concept was tested on NIST SRM 1648 Urban Particulate Matter (a composite of airborne particles collected in St Louis, Missouri) as well as on ground caffeine powder and various pure organic substances. 

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