Atomic absorption and atomic fluorescence methods of analysis: their merits and limitations

Abstract

Atomic absorption methods involve conversion of the sample into an atomic vapour and measurement of the absorbance of this vapour at a specific wavelength, characteristic of the analyte element. Flames and electrical furnaces are the most widely used means of atomization. Flame atomic absorption methods are rapid and precise, can be carried out on simple equipment, and are applicable to the determination of 67 elements. There have been no major recent advances in such methods. Electrothermal methods of atomization give much better sensitivity and are applicable to much smaller samples. They are generally less precise and slower than flame methods. There have, however, been important recent advances in electrothermal methods and further improvements in the near future are to be expected. There has been some progress in the development of atomization techniques based on cathodic sputtering. The main limitations of atomic absorption methods are associated with the incomplete atomization of the sample. Simultaneous multi-element analysis is generally not possible since the optimum atomization conditions vary according to the analysis to be carried out. Rapid sequential analysis is, however, now in widespread use. At present, atomic fluorescence methods are seldom used, possibly because they have most of the limitations of atomic absorption methods and are not so widely applicable. They are, however, superior for some analyses and many of these can be carried out on simple non-dispersive systems that have many attractive features. In this paper I discuss the merits and limitations of the atomic absorption methods of elemental analysis that have been developed during the past 30 years and are now in widespread use. I also discuss some of the methods developed during this period that involve the measurement of atomic fluorescence, a phenomenon having its origin in atomic absorption. These fluorescence techniques currently find little application in analytical laboratories but merit discussion in view of their many attractive features and their possibilities for further development.