Atomic Spectrometry Update–Atomic emission spectrometry

This Atomic Spectrometry Update is the latest in an annual series appearing under the title 'Atomic Emission Spectrometry'. The review describes developments in all aspects of atomic emission spectrometry, including fundamental processes and instrumentation.The renaissance of atomic emission spectrometry, brought about by the commercial introduction of the ICP about a quarter of a century ago, continues to flower. The major stimulus to research in recent years has undoubtedly come from another step change in technology, this time in the form of array detectors. There can be few areas of atomic emission spectrometry which have not been influenced by improvements in detector technology, as evidenced by the wide range of applications described in this year's Update. The ability to achieve simultaneous multi-element analysis across the full wavelength range is perhaps the most obvious advantage of these new detectors. However, the opportunities to interrogate multivariate data in a way not previously possible has spawned an entire research field devoted to the application of chemometrics. Examples of the use of principal component analysis, multiple least squares, multilinear regression, wavelets and neural networks have been published. The fact that measurements can be now made both rapidly and simultaneously has allowed the exploitation of transient signal measurement from sources, such as the single spark or laser ablation. The specific exploitation of this feature in terms of time-resolved analysis has been much in evidence. The use of CCD camera systems for spatial imaging of spectral sources has also been the subject of attention.In terms of source design, two areas stand out as being particularly active. The glow discharge is clearly the source of the moment, and developments in fundamental understanding are progressing in tandem with the design of new instrumentation. Supplementary excitation using rf, microwave, magnetic fields and pulsing of the basic dc discharge has remained a major field of research activity. This offers a great deal of scope for plasma diagnostic approaches, and the use of modelling and mathematical simulation has also been a recurrent theme in glow discharge research. The use of the laser as a primary emission source is undoubtedly on the increase, in part due to the development of rapid data acquisition signals to discriminate against non-specific background in the time domain. The compact nature and reliability of modern lasers also makes them attractive as portable analysers, particularly if the possibility of operation at atmospheric pressure in air is realised. The possibilities for practical depth profiling by LA-AES has moved closer with the recognition of the role of beam optics on ablation control.