FLOW-INJECTION ATOMIC SPECTROMETRY - A NEW ANALYTICAL TECHNIQUE

Much of the recent research in analytical atomic spectrometry has been concerned with problems of a practical nature. In particular, the inaccuracies arising from a variety of matrix effects and the limitations of sample introduction systems have provided a considerable driving force for recent developments in the various techniques. The philosophy of attempting to eliminate, or compensate for, interferences by procedures implemented at the atomization stage has had success for electrothermal atomization atomic absorption spectrometry but has proved of limited utility for other techniques. Despite considerable efforts, solid-sample introduction is still best done by procedures whose initial stage is dissolution. There is a steady growth in the flow-injection atomic spectrometric literature and a survey of the ca. 50 publications in 1990 shows that much of the interest is now centered on coupling preconcentration and matrix removal procedures with atomic spectrometry, although there is still work concerned with the basic characteristics of flow injection introduction, such as the reduction in sample loading, on-line dilution for calibration purposes and the ability to handle small sample volumes, being published. The role of the flow-injection valve as an interface between flow systems is highlighted. This interface allows independent optimization of the various flow systems coupled in this fashion. Several possible applications of recirculating closed-loop manifolds are described. These include the serial dilution of a stock standard for calibration purposes and to establish a working detection limit. This is illustrated by the dilution of a 2.45 mg l-1 solution of magnesium by a factor of 2.20 per injection. This procedure established a detection limit for the instrument involved of between 4.2 and 5.2 ng ml-1. The on-line acid leaching of calcium from charcoal is shown to be sufficiently precise for the basis of a rapid screening procedure and the determination of copper in matrices containing up to 50 g l-1 silver is made possible by the on-line precipitation of the matrix as the chloride in a circulating loop containing a filter column of nylon fibres. The additional possibilities afforded by these designs of manifold and the great variety of manifolds described in the literature suggest that flow-injection atomic spectrometry may be emerging as an analytical methodology analogous to the variety of procedures encompassed by terms such as liquid chromatography in the vocabulary of the analytical methodology for molecular species.