A novel capillary microplasma analytical system: interface-free coupling of glow discharge optical emission spectrometry to capillary electrophoresis

Abstract

It was found that a capillary electrophoresis (CE) process can be induced by starting a low-temperature d.c. liquid-electrode glow discharge (GD). A novel capillary microplasma analytical system (C-μPAS) was constructed by interface-free coupling of d.c. glow discharge optical emission spectrometry (GD-OES) to CE and was applied in elemental (speciation) analysis. A GD was generated at one end of a capillary, and initiated not only a capillary electrophoresis process but also a microplasma; a sample was injected at the other end of the capillary, separated by CE, and detected by GD-OES. This portable C-μPAS integrates introduction of the sample, separation of the analyte species, and detection of the analytical signal into one unit. The performance of this new analytical system was first evaluated by the analysis of a mixed aqueous solution of mercury, cadmium, chromium, sodium and organic or inorganic species without derivatization, and the absolute limits of detection (LODs) were found to be in the range of 0.5 to 500 picograms under the optimized experimental conditions. Preliminary experimental results for mercury speciation showed that it provided effective separation and results as accurate as those obtained by HPLC-ICP-MS. The working mechanism of this system is discussed, with the theoretically calculated electron temperature and electron density of the microplasma. This C-μPAS has the advantages of portable instrumentation, green chemistry (low power consumption, tiny sampling volume and almost no pollutants), high sensitivity (detection of optical emissions), low interference (separation by CE and spectral resolution), versatility (organic, inorganic, cationic or anionic analytes), and fast analysis (several minutes). It should have a very promising future in a range of areas such as environmental analysis, metallomics research, water analysis, online monitoring and field analytical chemistry.