Liquid sampling-atmospheric pressure glow discharge (LS-APGD) microplasmas for diverse spectrochemical analysis applications
Over the last 15 years there has been a great deal of interest in the potential development of spectrochemical sources that come with lower operational overhead than the inductively-coupled plasma (ICP). There are many driving forces for the development of such devices, even with the likely sacrifices in terms of analytical performance. Some of these devices operate in ambient atmospheres in the electrical regime of glow discharge (GD) plasmas, wherein one of the electrodes is an electrolytic solution that serves as the medium for sample introduction. The basic operational space and analytical performance of these devices has been reviewed in the recent past. We focus in this review on the design and operational attributes of the liquid sampling-atmospheric pressure glow discharge (LS-APGD) microplasma. The rationale for the development and basic source designs are first considered, followed by practical contrasts to the other devices provided. A number of studies have been performed to assess the fundamental plasma characteristics including kinetic and excitation temperatures, as well as charged particle densities. Perhaps the greatest difference between the LS-APGD and the other plasmas is the analytical versatility that has been demonstrated. Analytes can be determined by optical emission spectroscopy or mass spectrometry (OES/MS), with sampling regimes consisting of solution phase introduction, particles produced via laser ablation, or through an ambient desorption mechanism directly from the solid state. Finally, the microplasma can be operated in alternative modes wherein either elemental or molecular-form mass spectra are obtained. It is believed that the simplicity of the LS-APGD design, combined with its analytical versatility, suggest that this singular platform could be implemented to address diverse analytical challenges.