Microdischarge in Flame as a Source-in-Source for Boosted Excitation of Optical Emission of Chromium

Advances in atmospheric pressure plasma-based optical emission spectrometry for the analysis of heavy metals

Over the past decade, miniaturized optical emission spectrometry (OES) systems utilizing atmospheric pressure plasmas (APPs) as radiation sources have exhibited impressive capabilities in trace heavy metal analysis. As the core of the analytical system, APPs sources possess unique properties such as compact size, light weight, low energy requirement, ease of fabrication, and relatively low manufacturing cost. This critical review focuses on recent progress of APP-based OES systems employed for the determination of heavy metals. Influences of technical details including the sample introduction manner, the sampling volume, the sample flow rate, the pH of the solutions on the plasma stability and the intensity of analytical signals are comprehensively discussed. Furthermore, the review emphasizes the analytical challenges faced by these techniques and highlights the opportunities for further development in the field of heavy metal detection.

Array Point Discharge as Enhanced Tandem Excitation Source for Miniaturized Optical Emission Spectrometer

A new compact tandem excitation source was designed and constructed by using an array point discharge (ArrPD) microplasma for a miniaturized optical emission spectrometer through coupling a hydride generation (HG) unit as a sample introduction device. Three pairs of point discharges were arranged in sequence in a narrow discharge chamber to construct the ArrPD microplasma, for improved excitation capability owing to the serial excitation. Besides, the discharge plasma region was greatly enlarged, therefore, more gaseous analytes could be intercepted to enter into the microplasma for sufficient excitation, for improved excitation efficiency and OES signal. To better understand the effectiveness of the proposed ArrPD source, a new instrument for simultaneous detection of atomic emission and absorption spectral responses was also proposed, designed, and constructed to reveal the excitation and enhancement process in the discharge chamber. Under the optimized conditions, the limits of detection (LODs) of As, Ge, Hg, Pb, Sb, Se, and Sn were 0.7, 0.4, 0.05, 0.7, 0.3, 2, and 0.08 μg L^-1, respectively, and the relative standard deviations (RSDs) were all less than 4%. Compared with a commonly used single point discharge microplasma source, the analytical sensitivities of these seven elements were improved by 3-6-fold. Certified Reference Materials (CRMs) were successfully analyzed with this miniaturized spectrometer, which features low power, compactness, portability, and high detectability, and is thereby a great prospect in the field of elemental analytical chemistry.