Fluorescence spectroscopy as a tool for determination of coumarins by multivariate calibration.

At present, it is necessary to check the quality of many food products in which the content of coumarins is limited. Since a rapid and simple method for the determination of coumarin (COU), 4-hydroxycoumarin (4HC) and dicoumarol (DC) in tea samples was needed, we developed an alternative option to chromatography, i.e., fluorescence spectroscopy with multivariate calibration. The synchronous fluorescence spectra were recorded at constant wavelength differences 70, 80 and 90 nm from 200 to 400 nm. The different experimental parameters affecting the synchronous fluorescence intensities of the analytes were carefully studied and optimized. Partial least squares (PLS) method and multi linear regression (MLR) were compared on determining the concentrations. The best results were obtained by the PLS method on synchronous fluorescence spectra at Δλ = 90 nm. The results from the analysis of herbal tea Melilotus officinalis by synchronous fluorescence spectroscopy with PLS model are equivalent with the results from HPLC. Fisher F-test and Student's t-test confirmed this finding.