Flow-through amperometric methods for detection of the bioactive compound quercetin: performance of glassy carbon and screen-printed carbon electrodes

Rapid methods using batch injection analysis (BIA) with amperometric detection were developed for the determination of quercetin extracted from the Brazilian plants Brunfelsia uniflora (BU), Vismia guianensis (VG), and Arrabidaea brachypoda (AB). One method was based on a glassy carbon electrode (GCE) and pulsed amperometry (BIA-PA), while the other employed a screen-printed carbon electrode (SPCE) and conventional amperometry (BIA-CA). Both proposed methods required minimal sample manipulation (only dilution in the carrier electrolyte), and the determination was performed with a single injection of 100 μL of sample solution. The BIA-PA method was highly accurate ( RSD = 0.7%, n = 30), fast (120 injections h −1 ), and presented low limits of detection (0.004 μmol L −1 ) and quantification (0.015 μmol L −1 ). The BIA-CA method was also accurate ( RSD = 1.1%, n = 30), fast (120 injections h −1 ), and presented low limits of detection (0.027 μmol L −1 ) and quantification (0.091 μmol L −1 ). The application of the proposed methods for the determination of quercetin in the plant extracts provided results similar to those obtained by high-performance liquid chromatography (HPLC) at a confidence level of 95%.