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Using a coupling of ICP with a closed electrolyte cathode discharge ELCAD cell as nebulizer unit it was possible to observe a well defined element dependency of the cathode sputtering process on the electrolyte surface. Investigating the ICP signal ratio referred to the pneumatic nebulization, the ELCAD sputtering produces about three times higher mass transport for Al, Cr, Pb and Cd than for Mg and Cu. B, Ba and Ca have an even lower signal while Hg shows a “super-sputtering” effect, having a 17 times higher signal with ELCAD than with pneumatic nebulization. Assuming that positively charged particles are forced back to the cathode by the 107V m−1field in the cathode dark space these observations fit to the model of stepwise charge neutralization by hydrolysis in the vapor-phase, which process is known in mass spectrometry. The sputtering process in the ELCAD can be described with a four-zone kinematic model of the cathode dark space.

A capillary version of the atmospheric electrolyte cathode glow discharge ELCAD cell is described which could act as a multimetal detector for chromatographic or flow injection analysis applications. The sample that is fed into the cell is analyzed through cathode-sputtering of the electrolyte surface at the end of the capillary. In contrast to the earlier ELCAD cells having large electrolyte pool cathode of 2–3 cm diameter and 10 ml min−1flow rate, the novel cathode flow system consists of a glass capillary of 1 mm id. This new cell has a volume of 15 µl and requires only 3.5 ml min−1flow. Excellent discharge stability is achieved by using the “electrolyte wire” in an insulator capillary as a well defined central current route to the cathode layer of the discharge. Cathodic current density is substantially higher and the cathode fall value reaches 860 V, that is ∼50 higher than that at the large cathode pool surface. Fluctuation-dampened solution feeding provides further improvement in the position stability of the cathode layer of the plasma. Blocking of the anode glow emission in the plasma imaging optics greatly reduces the noise in the emission line intensity measurement. All these positive effects result in 0.5–1.2 ng absolute and 14–34 ppb concentration detection limits for Cd, Zn, Cu, Pb and Ni in a 37 µl injection volume.

The intensity of the spectral lines emitted by the electrolyte cathode glow discharge plasma was investigated as a function of the air pressure at different discharge currents and pH values of the cathode solution. The observed increase in the metal line intensity is explained by three-body collisional recombination of positive metal ions in the cathode dark space (M++e+e→M+e) followed by diffusion of neutral metal atoms into the negative glow, where electron impact excitation of the neutral atoms takes place. On the basis of these two processes, the dependence of the intensity on pressure was calculated by an approximating equation, giving an excellent agreement with the experimental results in the pressure range 530–1200 mbar. Furthermore, the model predicts the appearance of an intensity maximum as a function of the air pressure. This maximum was observed in preliminary experiments in the pressure range 1200–2300 mbar.