Determination of Quercetin and Luteolin in Paprika Samples by Voltammetry and Partial Least Squares Calibration

Abstract

Quercetin and luteolin are flavonoids with beneficious properties, which are present in paprika. In this work, both have been determined in paprika by using electrochemistry combined with chemometrics. The electrochemical oxidation mechanisms of both analytes have been studied through sampled direct current (DC) voltammetry, differential pulse voltammetry (DPV) and Square Wave Voltammetry (SWV), making use of a glassy carbon electrode. The final technique selected for the quantification was DPV due to its high repeatability with respect SWV. The chemical variables and the instrumental parameters were optimized and the final conditions employed were ethanol: water (20 : 80), 0.75 mol dm−3 of HCl, and a pulse amplitude of 50 mV. Due to the facts that oxidation potential of both analytes were quite similar, their DPV peaks were overlapped, and also because the analytes interaction during the electrochemical process causes a non‐additivity of the signals, they could not be quantified separately by direct measurement of peak intensity. For this reason, a chemometric algorithm was applied (partial least squares (PLS) regression in its modality PLS‐2). In the case of validation samples, appropriate sets of calibration and validation were built and good results were obtained. This methodology was applied to real paprika samples and the results were similar to those obtained with a HPLC method previously reported.

Analytical determinations of luteolin

“…At this point, it is important to highlight the work carried out by the group of Galeano-Díaz in which by moving the focus to data analysis instead of the electrode modification, they get good results (even in selectivity) through the use of a bare GCE together with a data analysis based on partial least squares analysis (PLS). 91 Probably in the case of luteolin determination in real samples, it is more important that the sensor has a wider linear range than that it has an extremely low LOD. In a sample with an unknown value of luteolin concentration, it is important that the measured value falls within the calibration curve to avoid errors.…”

“…Finally, an item that involves cost, portability, and stability is the simplicity of the electrode and/or the method used. At this point, it is important to highlight the work carried out by the group of Galeano‐Díaz in which by moving the focus to data analysis instead of the electrode modification, they get good results (even in selectivity) through the use of a bare GCE together with a data analysis based on partial least squares analysis (PLS) 91 …”

Simultaneous determination of quercetin and luteolin in mate and white tea samples

“…In the literature, individual or simultaneously determination of these molecules were carried out after some modification procedure or different calculation method (Table 2). 16,18,20,21,[24][25][26] In this study, the simultaneous determination of Qu and Lu was performed with high sensitivity and wide linear ranges using the unmodified GCE and calibration curve.…”

Simultaneous determination of quercetin and luteolin in mate and white tea samples

“…In the literature, there was only one study about the simultaneous electrochemical determination of Qu and Lu. 26 Chamizo-Gonzalez, Monago-Marana and Galeano-Diaz (2017) reported DPV and partial least squares.…”