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

Abstract

This paper reviews the most common methods of generation of plasmas using microwaves with special emphasis on recently developed microwave plasma (MWP) sources for analytical applications. The art and science of microwave plasma optical and mass spectroscopy instrumentation (MWP-OES/MS), and the applications are briefly presented, including very recent advances in the field as of 2012. The design and operation of MWPs is discussed to provide a basic understanding of the most important selection criteria when designing MWP systems. The various plasma generation systems described include single-electrode capacitive microwave plasmas, electrodeless inductively coupled plasmas, multi-electrode systems energized with stationary or rotating fields. We also discuss various technical realizations of MWP sources for selected applications. Examples of technical realizations of plasmas in closed structures (cavities), in open structures (surfatrons, planar plasma sources), and in magnetic fields (Hammer cavity) are discussed in detail. Finally, we mention micro-and mini-discharges as convenient sources for miniaturized spectrometric systems. Specific topics include fundamental aspects of MWP, i.e., recent advances in the construction of analytical MWPs (coaxially coupled cavities, strip-line technology, multi-point energizing, power combining, rotating fieldexcited plasmas), operational characteristics, analytical characteristics and applications. Special reference is made to coupling with OES for determination of chromatographic effluents and particle sizing. The developments in elemental and molecular MS applications in both low-power and high-power MWPs are also discussed.

GGR Biennial Critical Review: Analytical Developments Since 2012

“…While other plasma sources and types have been developed and tested (Montaser et al . , Jankowski and Reszke ), commercial hardware is focused solely on instruments using argon‐based ICP. Recently, however, a commercial microwave plasma (MP) AES system has been introduced onto the market, which appears to provide an attractive alternative to flame AAS and ICP‐AES.…”

“…Developments in instrumentation for MP sources have been reviewed by Jankowski and Reszke (). Historically, plasmas have used the energy from microwave electric field, leading to very thin, rodlike plasmas.…”

“…The quartz torch is positioned within the magnetic field maximum and obstructions placed within the waveguide alter the field patterns, acting as capacitors or inductors. The harmonically oscillating magnetic field (2450 MHz) generated by the conductor induces an electric field in which the plasma electrons are accelerated (Jankowski and Reszke ). The resulting plasma exists as a hollow tube that can be held away from the torch wall by a layer of fast flowing sheath gas (Figure ).…”

Evaluation of Five Phase Digitally Controlled Rotating Field Plasma Source for Photochemical Mercury Vapor Generation Optical Emission Spectrometry

“…Among other plasma sources, some interesting multi-electrode approaches of plasma powered by rotating fields have been reported, operating under different regimes including electrode arrangement and operating conditions such as power, frequency and gas flow. [12][13][14][15][16][17] Jankowski et al demonstrated that rotating field discharges operating at the kHz level could be analytically useful for determination of gaseous samples. 16,17 In the present work, a novel, on-line hyphenated system based on ultrasonic nebulization and photo-induced chemical vapor generation with digitally controlled rotating field plasma-optical emission spectrometry was developed and evaluated for the determination of mercury (USN-UV-CVG-RFP-OES).…”

“…Plasma sources including microwave plasmas (MWPs) have played an important role as radiation/ionization sources for atomic and molecular spectrometry. [12][13][14] The argon or helium microwave induced plasma (Ar-MIP or He-MIP) is commonly sustained at the atmospheric pressure in one-tube quartz or ceramic torches using cylindrical Beenakker resonant cavities, e.g., operated in TM010 modes, and surfactants. In recent years, compact helium plasma sources operating at atmospheric pressure have been of great importance in optical emission spectrometry (OES) as well as in mass spectrometry (MS).…”