Simultaneous Determination of Phenolic Acids and Scopoletin in Brandies Using Synchronous Fluorescence Spectrometry Coupled with Partial Least Squares

Brandy, a spirit drink produced from wine (grape), is rich in phenolic acids due to its maturation in wooden barrels. Phenolic acids play a significant role in defining the sensorial characteristics of wines and brandies, and therefore, it is very useful to determine them. Synchronous fluorescence spectra of mixtures containing phenolic acids (gallic, vanillic, syringic and ferulic) and scopoletin have been used for the determination of these compounds by partial least squares (PLS)2. Synchronous fluorescence spectra were collected by simultaneously scanning the excitation and emission monochromator in the excitation wavelength range 200-500 nm, with constant wavelength difference 100 nm between them. The leave-one-out cross-validation method was used to select the optimum number of five PLS2 components (latent variables). The PLS2 model captured for 100 % of variance in the spectral block, and it accounted for 99.34 % of variance in the concentration block. The performance of the model was evaluated by means of root mean square error of cross-validation, root mean square error of prediction and coefficient of determination. The best model was used for the determination of the above-mentioned compounds in brandy samples at concentration levels 2-74 mg L-1 for phenolic acids and 0.06-0.43 mg L-1 for scopoletin. The PLS2 results were found to be in good agreement with those obtained by HPLC method.