Dual-stage excitation source improves the analytical sensitivity of miniaturized optical emission spectrometer

Miniaturized optical emission spectrometric (OES) devices based on various microplasma excitation sources provide a reliable tool for in-situ elemental analysis. The key to improving analytical performance is enhancing the excitation capability of the microplasma source in these devices. Here, dielectric barrier discharge (DBD) and point discharge (PD) technologies are combined to construct an enhanced dual-stage excitation source (called DBD-PD), which improves the overall excitation efficiency and OES signal sensitivity. Specifically, DBD serves as a pre-excitation source in a narrow discharge chamber, significantly reducing energy consumption during breakdown discharge gas, while improving the excitation capability of subsequent PD microplasma. The microplasma parameter characteristics were calculated, and the microplasma state during the excitation process was imaged using a fast-gated intensified charge-coupled device (ICCD) camera, revealing the enhancement mechanism of the DBD-PD excitation source. Compared to other microplasma excitation sources such as DBD, PD and PD-DBD, DBD-PD increased Se and As signal intensity by up to 16.0 and 11.6 times, respectively. Under the optimal conditions, the detection limits of Se and As reached 0.8 and 0.2 μg L^-1, respectively, and the relative standard deviations (RSDs) were less than 5%. The analysis of certified reference materials (GBW07601a and GBW10023) and actual water samples verified the reliability and practicability of the proposed method. This analysis strategy not only offers significant leap in field performance of miniaturized OES devices but also holds extensive potential for broader applications in elemental analysis.