Atomic fluorescence spectrometry:
In atomic fluorescence spectrometry, the gaseous atoms acquired through flame or electrothermal atomisation are excited to higher energy levels through absorption of the electromagnetic radiation and the fluorescence emission from these excited atoms is measured. A fluorescence emission could occur by different pathways. Therefore, we have various types of atomic fluorescence transitions. The general types of atomic fluorescence transitions are termed as resonance fluorescence, Stokes direct line fluorescence, stepwise line fluorescence, two step excitation or double resonance fluorescence, sensitized fluorescence and thermal fluorescence. Of these, the thermally assisted fluorescence and sensitized fluorescence commonly are not employed for analytical reasons.
The intensity of the fluorescence radiation is measured at right angles to the direction of incident radiation and is associated to the concentration of the element present, creating the basis of quantitative analysis. In quantitative atomic fluorescence spectrometric determinations the instrument is commonly standardised through a calibration curve. The graph is drawn among the logarithms of the intensity of atomic fluorescence signal versus the log of analyte concentration. The linearity of like curves extends over 3 to 5 sequences of magnitudes. Thus, at higher concentration, linearity is lost because of self absorption.