Determination of bismuth by optical emission spectrometry with liquid anode/cathode atmospheric pressure glow discharge

Abstract

Novel atmospheric pressure glow discharge (APGD) microplasma systems, sustained between a miniaturized flowing liquid anode (FLA) or cathode (FLC) and a He nozzle jet were investigated for the determination of Bi with the aid of optical emission spectrometry (OES). The most influential working conditions, i.e., the acid type, the acid concentration, the discharge current, the He flow rate, the sample flow rate, and the discharge gap, were optimized for both studied methods. Furthermore, the effect of the addition of low molecular weight organic compounds (LMWOCs) into FLA/FLC solutions on the signal intensity of Bi was investigated. It was found that the addition of formic acid (5%) into the FLC solution enhanced the signal intensity 10 times. Under the optimized conditions, detection limits (DLs, assessed on the basis of the 3σ criterion) reached 33 μg L⁻¹ for the FLC-APGD system and 0.34 μg L⁻¹ in the case of the FLA-APGD system. The DL of Bi offered by the FLA-APGD-OES method was better than those reported for other microplasma techniques. The latter method was successfully applied for a quantitative determination of Bi in spiked water samples. The influence of concomitant ions on the signal intensity of Bi was thoroughly studied and the recoveries of Bi added to these water samples (at a concentration of 100 μg L⁻¹) were within the range of 86–101%, confirming the good accuracy and usefulness of the developed FLA-APGD-OES method.