A novel solution cathode glow discharge geometry for improved coupling to optical emission spectrometry

The Solution-Cathode Glow-Discharge (SCGD) is an atmospheric pressure glow discharge used for atomic emission spectrometry that is typically sustained between a metallic pin-anode and a liquid cathode, wherein sample solutions are introduced as a flowing stream emanating from a cylindrical capillary. A novel SCGD is reported here which sustains the SCGD plasma in a horizontal arrangement between a flat anode and a cathode constructed from a thin, rectangular capillary. This new arrangement creates a sheet-like plasma in which the negative glow of the SCGD approximates the shape of the entrance slit of a spectrophotometer, improving the efficiency of optical sampling. The analytical capability of the horizontal cathode SCGD is compared with a conventional SCGD and found to improve sensitivity and decrease limits of detection as much as 33-times for the 24 elements examined. Improvement is particularly significant for elements whose atomic emission is concentrated near the liquid cathode surface. The current/voltage characteristics and spatial distribution of atomic emission of the SCGD are reported, matrix effects associated with the design are examined, and a simple preconcentration technique for ground water analysis is also explored.