Temporal resolved atomic emission spectroscopy on a pulsed electrolyte cathode discharge for improving the detection sensitivity of Cu

Abstract

Atmospheric pressure electrolyte cathode discharge plasma presents a great potential on detecting heavy metal pollutants. In this paper, a novel microsecond pulsed electrolyte cathode discharge was generated and coupled with temporal resolved atomic emission spectra to analyze Cu element, as one of the representative heavy metals. The waveforms of voltage and current, as well as optical emission spectra of discharge were investigated, and the experimental conditions were optimized. The spatiotemporal resolved spectra of Cu I (324.8 nm), OH (A2Σ–X2Π) and N2 (C3Πu–B3Πg) were diagnosed. The spatiotemporal distributions of gas temperature and electron density were calculated by the rotational temperature of OH (A) and the Stark broadening of Hβ (486.1 nm), respectively. It was found that the optimal detection sensitivity of Cu are obtained under the conditions of HNO3 solution with 1.0 pH value, 3.0 mL/min solution flow rate, 8.5 kV pulse peak voltage, and 100 μs pulse width. The interferences of spectral line of Cu I (324.8 nm) are mainly sourced by the spectral bands of N2 (C-B) and OH (A-X), which could be reduced by the temporal resolved spectra. The limit of detection of Cu was improved from 0.217 mg/L to 0.092 mg/L by acquiring spectra only in 25–100 μs, under the optimal conditions. Furthermore, the gas temperature and electron density play important roles in the spatiotemporal evolution of discharge and the improvement of detection sensitivity for elemental analysis.