A portable piezoelectric transformer microplasma optical emission spectrometry for the determination of mercury

Miniaturization of microplasma-based optical emission spectrometry (OES) has gained great attention due to the advantages of simplicity, compactness, and cost-effectiveness. However, the energy feed-in affects the generation, maintenance and excitation capability of discharge microplasma, which also limits the potential of microplasma for portable OES. Herein, we report that a piezoelectric transformer-driven microplasma (PTM) was first utilized as an excitation source of miniature OES for quantitative analysis of mercury (Hg). A piezoelectric transformer (PT) can directly convert mechanical energy into electrical energy and emanate plasma at the wire of the output distal end, which provides a path to construct microplasma devices without an extra high voltage power supply. A syringe needle acted as another ungrounded electrode, which was hung a proper distance below the PT output, to generate glow discharge. Hg was effectively converted into volatile species by hydride generation (HG) and transferred into PTM through the syringe needle by carrier gas (argon). Under the optimized experimental conditions, Hg was detected in the range of 10–1000 μg/L, with a limit of detection (LOD) of 2.8 μg/L by using the analytical line of Hg 253.65 nm. The accuracy and practicability of the proposed method were validated by analyzing the Certified Reference Materials (CRMs, dogfish liver and soil) and real water samples with satisfied results. In addition to no need of high voltage power supply and closed circuit, this HG-PTM-OES system features low power consumption, small size, light weight, sturdiness and high safety, which would be beneficial to fabricate a miniaturized and portable device for on-site environmental monitoring.