Approaching the Limit in Atomic Spectrochemical Analysis

摘要

In atomic spectrochemical methods of analysis, the sample to be analyzed is decomposed into its constituent atoms and the atoms subsequently probed by atomic emission, absorption, or fluorescence. In such methods, it would seem to be straightforward to achieve extremely low detection limits, perhaps approaching the single-atom level, since atoms to be probed are in the vapor state, yield extremely narrow spectral lines, and should be relatively unaffected by other sample constituents. However, a number of factors conspire to limit sensitivity and detectivity in atomic spectrochemical techniques. Among these limitations are the relative inefficiency of most methods currently used for forming the free atoms, the ordinarily brief time available for atom observation which exists after sample decomposition is complete, and the residual background signal which accompanies most atomic spectral measurements. In this paper, a number of recent and proposed techniques to overcome these obstacles will be reviewed and evaluated, with a view toward assessing the present and future practicability of single-atom detection (SAD) methods will be reviewed and new methods will be examined for improving the atomization efficiency of real samples. Techniques for trapping ions or atoms for longterm observation will be considered and methods for improving the selectivity of atomic techniques will be assessed; these later techniques are based alternatively on spectral, temporal, or chemical characteristics of the elements being sought. (Author)