Optimization of discharge parameters for a flat-type radio-frequency glow discharge source coupled to a quadrupole mass spectrometer system

A radio-frequency (rf)-powered glow discharge (GD) atomization/ionization source for nominally flat sample types (>6 mm o.d.) has been designed and coupled to a commercial GD mass spectrometer system, the VG GloQuad. This source was evaluated and optimized for conducting as well as nonconducting samples. A parametric study has been conducted on this rf-GDMS system with respect to discharge power, Ar flow (cell pressure), limiting orifice plate (anode) diameter, and ion sampling distance. Analytical characteristics under the optimized source parameters-including stabilization times (5 min for conducting samples, 60 min for nonconducting samples); repeatability (overall internal <2% RSD, overall external 18% RSD employing ion beam ratios); quantification; and detection limits-were evaluated for both conducting and nonconducting samples.