Electrothermal Vaporization for Universal Liquid Sample Introduction to Dielectric Barrier Discharge Microplasma for Portable Atomic Emission Spectrometry

Abstract

Direct introduction of liquid sample into a microplasma for analytical atomic spectrometry can be a problem for its lowered atomization/excitation capability or can even extinguish it. The low power dielectric barrier discharge (DBD) microplasma has been widely used in optical spectrometry, but the number of detectable elements by atomic emission spectrometry (AES) is very limited, partially for the same reason. Here we use electrothermally vaporized analyte-containing species for sample introduction into a DBD microplasma, together with simple heating of the DBD, to enhance its atomization/excitation capability for AES. A compact tungsten coil electrothermal vaporizer (W-coil ETV) was used in this work, onto which a tiny volume of liquid sample was pipetted. Through administrating the heating program for the W-coil, sample solvent and matrix were removed first and subsequently atomized/vaporized analyte with extra energy provided by the W-coil was swept directly into the DBD microplasma for further atomization/excitation. These significantly contribute the stability of the DBD microplasma and save its power for reatomization/excitation of analyte thus improving the detectability. Under optimized experimental conditions, limits of detection of 0.8 μg L(-1) (0.008 ng) for cadmium and 24 μg L(-1) (0.24 ng) for zinc were obtained, with relative standard deviation (RSD) of 3.2% for 5 μg L(-1) Cd and 3.7% for 100 μg L(-1) Zn. Its potential application was also demonstrated by successfully analyzing several Certified Reference Materials. Its characteristics including compactness, low power consumption, cost effectiveness, tiny sample requirement, and easy operation make it very promising for field analytical chemistry.