Optimization of hollow cathode diameter for particle beam/hollow cathode glow discharge atomic emission spectrometry

An evaluation of the effect of cathode diameter on analyte emission intensity for the particle beam/hollow cathode glow discharge atomic emission spectroscopy (PB–HC–AES) system is described. A high-efficiency thermoconcentric nebulizer is used to generate a fine aerosol of the aqueous solution flowing at rates of ∼1 ml/min. Desolvation and use of a momentum separator/particle beam interface serves to introduce analyte particles into a heated HC glow discharge source for subsequent vaporization, atomization and excitation. The effects of discharge gas (He) pressure and current on emission responses for sodium and copper are evaluated in flow injection mode using 200-μl injection volumes for a series of fixed-length (25 mm) cylindrical HC having inner diameters of 2, 3, 5 and 7 mm. Analytical response curves obtained with the 2-mm i.d. HC for sodium and copper yield detection limits of 0.6 and 1.3 ppb in elemental Na and Cu, respectively, with less than 10% relative standard deviation (R.S.D.) for triplicate injections over a concentration range of 0.5–20 ppm.