Fluorescence Spectroscopy in Quantitative Analysis:

You have learnt previously that spectrophotometry is a good tool for the determination of concentration of the analyte. Therefore, at much lower concentration (ng level) of the substances, the fluorescence spectrometry scores over spectrophotometry.  It has come to the fore front in utility since of higher sensitivity of the fluorimetric determinations within comparison along with usual UV-visible spectrophotometry.  In addition, fluorimetry is more selective than UV-visible absorption spectrometry. It is more chosen on two counts. First, a number of molecules absorb strongly within the UV or visible range but do not exhibit detectable fluorescence. Another, in case of fluorescence two wavelengths (excitation and emission) is available while only a single wavelength is available in spectrophotometry.  Two samples having same absorption spectra might be distinguished if they fluoresce at various wavelengths. Same, two analyte molecules having same fluorescence spectra might be differentiated through proper choice of excitation wavelength (selective excitation).