HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY OF PHENOLIC ALDEHYDES WITH HIGHLY SELECTIVE FLUOROMETRIC DETECTION BY MEANS OF POSTCOLUMN PHOTOCHEMICAL DERIVATIZATION

Postcolumn photochemical derivatization was used in the HPLC with fluorimetric detection of polyphenolic aldehydes in samples which also have present phenolic acids at higher concentrations. This is the most common situation in many food and agricultural samples. Phenolic aldehyde photoproducts give highly sensitive fluorescent signals whereas for some phenolic acids with native fluorescence this property disappears as a consequence of the photoreaction. Individual parameters for each polyphenolic photoproduct (excitation and emission wavelength) were investigated, which allowed the resolution of complex mixtures to be optimized. The selectivity can be improved even further by means of time-programmed changes in the excitation/emission wavelength pairs in the fluorescence detector during the chromatographic elution.