DC glow discharge includes of the separate regions, Aston dark space, cathode glow, cathode dark space, negative glow, faraday dark space, positive column, anode dark space.
Plasma regions were distinguish, especially at 300 and 400 volts, where the peaks at 3.3 cm and 3.9 cm represent the negative glow and the cathode glow in addition to areas of darkness between them.
Following this pioneering study, significant variations of the ELCAD design have been developed, including solution cathode glow discharge (SCGD) [9, 10], direct current atmospheric pressure glow discharge (DC-APGD) [11, 12], liquid sampling-atmospheric pressure glow discharge (LS-APGD) [13, 14], liquid electrode plasma atomic emission spectroscopy (LEP-AES) [15, 16], alternating current electrolyte atmospheric liquid discharge (AC-EALD) [17, 18], drop spark discharge (DSD) [19, 20], and liquid electrode chip discharge [21, 22].
Recently, based on the principle of ELCAD, we also successfully developed a novel liquid cathode glow discharge-atomic emission spectrometry (LCGD-AES) for the simultaneous determination of multimetal elements in water samples  and ores samples , in which the glow discharge is sustained between a needle-like Pt anode and the electrolyte (as cathode) overflowing from a quartz capillary.
The liquid cathode glow discharge-atomic emission spectrometry (LCGD-AES) was successfully applied for measurement of K, Ca, Na, and Mg in salt mines samples.
Zhu et al., "Evaluation of flow injection-solution cathode glow discharge-atomic emission spectrometry for the determination of major elements in brines," Talanta, vol.
Zuev, "Use of electrolyte jet cathode glow discharges as sources of emission spectra for atomic emission detectors in flow-injection analysis," Journal of Analytical Chemistry, vol.
Shi, "Determination of trace heavy metals in environmental and biological samples by solution cathode glow discharge-atomic emission spectrometry and addition of ionic surfactants for improved sensitivity," Talanta, vol.
Lu et al., "Evaluation of liquid cathode glow discharge-atomic emission spectrometry for determination of copper and lead in ores samples," Talanta, vol.