Analytical performance of commercially available and unavailable phenolic compounds using real samples by high-performance liquid chromatography-diode-array detection

This work examines a novel approach of coupling high-performance liquid chromatography with diode-array detection as applied to the study of the analytical performance of the main phenolic classes contained in real samples. The chromatographic behavior of the main phenolic classes (benzoic and cinnamic acids and flavan-3-ols, flavonols and flavones as subclass of flavonoids) is carefully examined using real legume samples. Extracts from lentils proved to be excellent "real sample" because they contained the most important classes of phenolics that were subjected to current analysis. Benzoic and cinnamic acids, flavan-3-ols, flavonol and flavones, were definitely or provisionally identified. Robustness, extraction efficiencies and accuracy were thoroughly scrutinized to reach quality results. Extracts showed an excellent stability according to their retention times in relative standard deviation (R.S.D. < 3%) and high reproducibility in peak area (R.S.D. < 5%). High reproducibility was also observed in calibration slopes (R.S.D. < 7%). Detection limits ranged between 0.09 and 0.64 mug/ml and, thus, showed full capacity for the determination of these compounds. Accuracy was carefully evaluated by studying extraction efficiencies and recoveries from well-known phenolic standards. The high recoveries (greater than or equal to95%) obtained from the well-known phenolic structures of all representative phenolic classes allowed us to evaluate the accuracy of poorly known and commercially unavailable phenolic structures. The satisfactory analytical performance of currently employed methods had justified their recruitment for the quantification of phenolics in the study samples. (C) 2002 Elsevier Science B.V. All rights reserved.