Liquid sampling-atmospheric pressure glow discharge optical emission spectroscopy detection of laser ablation produced particles: A feasibility study

The use of a liquid sampling-atmospheric pressure glow discharge (LS-APGD) microplasma source as an alternative to conventional inductively coupled plasma (ICP) detection of laser ablation (LA) produced particles using a Nd:YAG laser at 1064 nm is demonstrated. This configuration utilizes a 180° geometry, which is different from the 40° geometry that was used to ionize ablated particles followed by mass spectrometric detection. The use of a hollow counter electrode (nickel, 0.3 cm o.d., 0.1 cm i.d.) was implemented to introduce ablated particles directly into the APGD plasma with helium as a carrier gas. The LS-APGD source was optimized using ablated copper as the test sample (helium carrier gas flow rate (0.30 L min− 1 He), discharge current (60 mA), laser power (44 mJ), and solution electrode sheath gas (0.2 L min− 1 He) and solution flow rates (10 μL min− 1 5% HNO3)). Standard brass samples having known Zn/Cu percentages were ablated and analyzed using the LS-APGD source. As a comparison, the established technique of laser-induced breakdown spectroscopy (LIBS) was used to analyze the same set of brass standards under similar ablation conditions to the LS-AGPD measurements, yielding comparable results. The Zn/Cu ratio results for the LS-APGD and LIBS measurements showed good similarity to previous measurements using ICP-MS detection. The performance of the LS-APGD–OES microplasma, comparable to well established methods, with lower capital and operational overhead expenses, suggests a great deal of promise as an analytical excitation source.

► Particles formed by laser ablation are readily introduced to the LS-APGD microplasma.
► The low power microplasma has sufficient energy to vaporize laser produced particles.
► Qualitative analysis of brass alloys is performed using a simple OES ratio method.
► The qualitative performance of the LS-APGD microplasma is on-par with LIBS analysis.