Microwave Plasma Systems in Optical and Mass Spectroscopy

Abstract

The art and science of microwave plasma (MWP) optical and mass spectroscopy is briefly presented including very recent advances in the field up to 2011. The use of MWPs as radiation sources for optical emission spectroscopy (OES) and atomic fluorescence spectroscopy (AFS) and as atom reservoirs for atomic absorption spectroscopy (AAS), cavity ringdown spectroscopy (CRDS), and laser‐enhanced ionization spectroscopy (LEIS) as well as ion sources for mass spectrometry (MS) is treated. Devices for producing both E‐type capacitively coupled microwave plasma (CMP)‐electrode and microwave‐induced plasma (MIP)‐electrodeless MWPs, including inductively coupled plasma (ICP)‐like H‐type plasmas, are classified and discussed, in addition to methods of their diagnostics, and results for the analytically relevant plasma parameters are presented. The means of generation of symmetrical plasmas and uses of microplasma devices are also presented with an effort to comment on general classification of microwave (MW) cavities. Further, the use of MWs for boosting of glow discharges (GDs) is treated along with other tandem sources. Methods for the introduction of gaseous, liquid, and solid samples into the MWP are discussed. They include direct vapor sampling (DVS), chemical vapor generation (CVG), and hydride generation (HG) techniques; dry aerosol generation techniques (electrothermal vaporization (ETV); spark ablation (SA); laser ablation (LA); and continuous powder introduction (CPI) as well as wet aerosol generation techniques using both solution and slurry nebulization. Special reference is made to coupling with gas chromatography (GC) and also with various separation techniques for liquids including high‐performance liquid chromatography (HPLC). The analytical figures of merit in the case of OES with low‐power and high‐power MIP, CMP, microwave plasma torch (MPT), MWP‐electrode sources including rotating field sustained plasma and H‐type MWP as well as microplasmas are given. There are also described cases of atomic absorption, fluorescence, and laser ionization with these sources. The developments in MS in the case of both low‐power and high‐power MWPs and in the case of various types of sample introduction techniques are discussed. Applications of MWP analytical spectroscopy are in the fields of biological samples with special reference to microanalysis, and of environmental and industrial samples with special emphasis on element speciation, on‐line monitoring, particle sizing, and direct solids analysis. A critical comparison of the methodology with other spectroscopic methods for the determination of the elements and their species is given.

Effect of temperature on direct chemical vapor generation for plasma optical emission spectrometry: An application of programmable temperature spray chamber

“…It is clear that MIP source is more vulnerable for water aerosol loading as confirmed by many authors [22,23]. The potential benefits from increased sample transport efficiency at higher PTSC temperatures are suppressed by plasma overloading which is also a sure reason of plasma decay.…”

Contemporary Research Progress on the Detection of Polycyclic Aromatic Hydrocarbons

“…Among them, a remarkable high-frequency plasma source, microwave plasma torch (MPT), was invented initially by Jin’s Group [ 124 ], and was substantially promoted by Gary M. Hieftje’s group [ 125 ]. MPT easily generated a stable and visible flame-like plasma at atmospheric pressure and operated at commercial 2.45 GHz, by which the plasma operation was significantly improved [ 126 ]. MPT offered a much better analytical performance for the introduction of aqueous aerosols.…”

Recent developments in instrumentation of microwave plasma sources for optical emission and mass spectrometry: Tutorial review

“…Among them one can mention CMP plasma cavities 2,38-43 and MPT, 15,44,45 and also E-excited MIP cavities in which the plasma is exposed to a strong electric eld, usually directed along the plasma column. [2][3][4]6,10,20,21,34,35 The H-type devices are all MIPs. The harmonically oscillating magnetic eld generated by the conductor induces an electric eld in which the plasma electrons are accelerated.…”

“…Plasma sources including microwave plasmas (MWPs) have played an important role as radiation/ionization sources for atomic and molecular spectrometry. [1][2][3][4][5] Through this tutorial we seek to present the reader with an overview MWP of approaches for analytical spectrometry. This includes developments in devices needed for producing laboratory stand-alone high power MWP spectrometers, as well as the less powerful miniaturized systems.…”

“…Although this tutorial concludes with some representative applications of MWPs in analytical spectrometry, the interested reader is encouraged to refer to recent technical reviews and the current analytical spectrometry literature for more detailed information on different applications. [1][2][3][4][5][29][30][31] 2 Historical perspective Since the origins of modern MWP sources date back to the mid-20th century, some history is worth reviewing for attempts to sustain a stable plasma able to absorb a considerable amount of analytical sample.…”