Microwave Plasma Systems in Optical and Mass Spectroscopy

Abstract

AbstractThe 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.