Parametric evaluation of ambient desorption optical emission spectroscopy utilizing a liquid sampling-atmospheric pressure glow discharge microplasma†
An evaluation of the parametric dependence of emission responses for ambient desorption optical emission spectroscopy utilizing a liquid sampling-atmospheric pressure glow discharge (AD-OES-LS-APGD) microplasma is described. The influence of optical sampling position, acid type, sample matrix, solution flow rate, discharge current, sample displacement, angle of solution electrode interelectrode separation, and gas flow rates on the emission response of copper as the model matrix and analyte are investigated. The type of acid plays a major role in the emission response of copper suggesting a possible reaction-based desorption process on the surface of the sample. The physical make-up of the matrix (bulk or thin film) has no major effect on the emission response. The incidence angle between the solution electrode and the target surface is shown to have a major influence on emission response, indicating that the momentum of the sheath gas plays some role in desorption or transport of vaporized material to the plasma. There is positive correlation between solution flow rate, electrode distance, and emission response while only a minor emission dependence is seen from sheath gas flow rate. A region of intense emission is observed in spatial profiling experiments. Further development will be directed towards a field deployable ambient source for analysis of solid samples with no requirement of sample preparation.