Effects of anode geometry on the analytical performance of solution-cathode glow discharge for alkali metal detection by atomic emission spectroscopy

The effect of anode geometries on the analytical performance of the solution-cathode glow discharge (SCGD) source was investigated using tungsten rods with varying diameters and conical angles for atomic emission spectroscopy (AES). Under optimal operational parameters (electrolyte solution: HNO₃ at pH 1.0, discharge current: 65 mA, solution flow rate: 1.9 mL min⁻¹, and discharge distance: 2.0 mm), the highest emission intensity and stability for Na, Rb, K, Li, and Cs were obtained at the tungsten rod with a diameter of 2.4 mm, with relative standard deviations (RSD) of 1.14%, 0.93%, 1.01%, 1.25%, and 0.94%, respectively, while achieving the best detection limits (DLs). Additionally, when the anode tip had a conical angle of less than 30°, thermal melting resulted in discharge instability. A conical angle greater than 90° induced thermal spreading, leading to instability. Higher emission intensity stability and lower DLs were achieved with a conical angle of 60°. These results may provide new insights for enhancing the performance of SCGD systems.