AC needle-to-needle bare electrode discharge with nebulized sample injection for elemental analysis

Abstract

In this study, atmospheric pressure AC needle-to-needle bare electrode discharge coupled with a nebulized sample injection was developed for elemental analysis (Ni, Cu, Cd, and Pb). The effects of various parameters—including carrier gas composition, nebulizer gas flow rate, organic additives, solution pH, discharge power, and discharge gap—on the discharge mode and analytical performance were systematically investigated. Oxygen was identified as the optimal carrier gas due to its low background noise in the optical emission spectrum and favorable plasma properties. Importantly, the transition state between streamer and glow-like discharge was found to be most favourable for elemental analysis. Under optimized conditions (2.2 L min⁻¹ nebulizer gas flow rate, 2% methanol additive, 3 mm discharge gap, and 15 kV applied voltage), the device achieved sensitive limits of detection (LODs) for Ni (0.38 mg L⁻¹), Cu (0.05 mg L⁻¹), Cd (0.09 mg L⁻¹), and Pb (0.24 mg L⁻¹), with relative standard deviations (RSDs) ≤6.1% (n = 10), demonstrating its potential for portable and rapid elemental analysis applications.