Commercial Atomic Emission Systems

Providing lists of commercial manufacturers and types of instruments is a dangerous business, as instrument company takeovers, sell-offs, and the usual yearly introduction of new instruments, sometimes with only minor changes but with new names, occur on a frequent basis. The instrument company websites should be consulted for current details. There are also many companies who manufacturer instruments with limited geographic distribution who are not included in the discussion. This list is not inclusive or comprehensive, but is meant to give the student a feeling for the types of instruments commercially available at the present time. 

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In recent years plasma MS has become very popular, especially where the ion source for the mass spectrometer is an ICP. These systems, which are available commercially, offer detection limits two to three orders of magnitude better than those for atomic emission detection (i.e. subpicogram levels for some elements)... 

MIP-AED GC GG-heated transfer line-AED pg element P e.g., 2pgkg butyltin in sediment 0.01-0.03 pgkg organolead compounds in peat Commercial systems detector based on atomic emission non-volatile compounds require derivatization 417,421... 

AES would be expected to suffer from chemical interferences and spectral interferences, as do the other atomic emission techniques we have discussed. The focus will be on the commercial instmments available and on the graphite furnace-laser system. 

Initially hydride generation and cold vapour techniques were developed for the quantitative determination of the hydride-forming elements and mercury by atomic absorption spectrometry (Chapters, Sections 6.2 and 6.3), but nowadays these methods are also widely used in plasma atomic emission spectrometry. In the hydride generation technique, hydride-forming elements are more efficiently transported to the plasma than by conventional solution nebulization, and the production and excitation of free atoms and ions in the hot plasma is therefore more efficient. Spectral interferences are also reduced when the analyte is separated from the elements in the sample matrix. Both continuous (FIA) and batch approaches have been used for hydride generation. The continuous method is more frequently used in plasma AES than in AAS. Commercial hydride generation systems are available for various plasma spectrometers. 

To overcome the problem of detection in CE, many workers have used inductively coupled plasma-mass spectrometry (ICP-MS) as the method of detection. Electrochemical detection in CE includes conductivity, amperometry, and potentiometry detection. The detection limit of amperometric detectors has been reported to be up to 10 M. A special design of the conductivity ceU has been described by many workers. The pulsed-amperometric and cyclic voltametry waveforms, as well as multi step wave forms, have been used as detection systems for various pollutants. Potentiometric detection in CE was first introduced in 1991 and was further developed by various workers. 8-Hydroxyquinoline-5-sulfonic acid and lumogallion exhibit fluorescent properties and, hence, have been used for metal ion detection in CE by fluorescence detectors. Overall, fluorescence detectors have not yet received wide acceptance in CE for metal ions analysis, although their gains in sensitivity and selectivity over photometric detectors are significant. Moreover, these detectors are also commercially available. Some other devices, such as chemiluminescence, atomic emission spectrometry (AES), refractive index, radioactivity, and X-ray diffraction, have also been used as detectors in CE for metal ions analysis, but their use is stiU limited. 

HPLC-QFAAS is also problematical. Most development of atomic plasma emission in HPLC detection has been with the ICP and to some extent the DCP, in contrast with the dominance of the microwave-induced plasmas as element-selective GC detectors. An integrated GC-MIP system has been introduced commercially. Significant polymer/additive analysis applications are not abundant for GC and SFC hyphenations. Wider adoption of plasma spectral chromatographic detection for trace analysis and elemental speciation will depend on the introduction of standardised commercial instrumentation to permit interlaboratory comparison of data and the development of standard methods of analysis which can be widely used. 

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