A Microwave-Induced Plasma Based on Microstrip Technology and Its Use for the Atomic Emission Spectrometric Determination of Mercury with the Aid of the Cold-Vapor Technique

Abstract

A new low-power, small-scale 2.45 GHz microwave plasma source at atmospheric pressure for atomic emission spectrometry based on microstrip technology is described. The MicroStrip Plasma (MSP) source was produced in microstrip technology on a fused-silica wafer and designed as an element-selective detector for miniaturized analytical applications. The electrodeless microwave-induced plasma (MIP) operates at microwave input power of 10-40 W and gas flows of 50-1000 mL.min-1 of Ar. Rotational (OH) and excitation (Fe) temperatures were found to be 650 and 8000 K, respectively. Spatially resolved measurements of the Hg I 253.7-nm atomic emission line with an electronic slitless spectrograph (ESS) showed that a cylindrically symmetric plasma with a diameter of about 1 mm is obtained. With the MSP, Hg could be determined by applying the flow injection cold vapor (FI-CV) technique with a detection limit of 50 pg.ml-1. In terms of the relative standard deviation, a time stability of < 1.4% for 45 replicates within 80 min can be realized at a concentration level of 10 ng.ml-1 of Hg. Hg could be determined in the leachate of a certified standard reference soil (STSD-4) obtained by treatment with aqua regia at the 930 +/- 76 ng.g-1 level. Results obtained by calibration with aqueous solutions of Hg and with standard addition were found to be in good agreement with those of cold-vapor atomic absorption spectrometry.

Evaluation and application of argon and helium microstrip plasma for the determination of mercury by the cold vapor technique and optical emission spectrometry

“…The detection limit based on the 3σ blank criterion was found be 0.64 ng mL −1 and is comparable to that reported lately for the CV microwave-induced plasma OES system with a microwave plasma torch [20]. It is somewhat higher than the value of 0.05 ng mL −1 reported by Engel et al [7], which may be due to the poorer resolution of the spectrometer used for our measurements. The measurement precision, expressed by the relative standard deviation (RSD) for n=3, for low concentrations of Hg, i.e., from 5 to 20 nm mL −1 , varied from 9 to 3%.…”

“…In the literature, the use of different electrodeless microdischarges and discharges operated with electrodes, comprising the microwave-induced microstrip plasma (MSP) [6,7], the capacitively coupled microplasma [8], the direct current glow discharge microplasma [9], the stabilized capacitive plasma [10], and the microfabricated inductively coupled plasma [11], has been reported so far, mainly for the purpose of the determination of different analytes in the gaseous phase. They included different volatile hydrocarbons, their chlorinated derivatives, or other molecular gases such as SO 2 .…”

“…So far, the analytical features of the microwave-induced plasma based on microstrip technology have been demon-strated by the determination of Hg in aqueous solutions through the cold vapor (CV) generation technique [7]. This situation can be attributed to the rather limited capabilities of the microplasma excitation sources to evaporate water vapor originating from the gas-liquid phase reaction/ separation process or other reaction by-products accompanying the introduced volatile species of the analytes.…”

Sample Analysis with Miniaturized Plasmas

“…It could be used with 0.5 L/min of argon and a power of 15 W in conjunction with the mercury cold vapor technique for the determination of mercury, with detection limits down to 50 pg/mL and excellent short-and long-term precision. 8 For leachates of soils, accurate determinations of traces of mercury were shown to be possible. The chip could still be made smaller by using a 30 ϫ 30 mm 2 quartz plate 1.5 mm thick in which a cylindrical channel with a diameter of 0.9 mm is provided parallel to the surface.…”

Micromachined chip-scale plasma light source

“…Research to date on micromachined plasma source has been on unsealed electrode arrays, typically atmospheric plasmas for medical or chemical applications [1][2][3], gas chromatography [4] or spectroscopy [5,6]. We have developed a sealed chip-scale plasma light source that is low power (as required for portable applications), versatile and compact, with efficient operation at 10-500 mbar in different gases (Ar, He and N 2 ) [7].…”