Highly-sensitive Electrochemical Methods For The Detection Of Quercetin And Protocatechuic Aldehyde Based On The Signal Enhancement Of Activated Silica Gel

Silica gel has obtained wide applicaions due to large surface area and strongadsorption ability. In this paper，a simple method was used to activate silica gel, and it wasfound that the electrochemical activities of activated silica gel were greatly improved. As aresult, highly-sensitive electrochemical methods was individually developed for thedetection of quercetin and protocatechuic aldehyde. Main work is as follows:1. Preparation and characterization of activated silica gel. Column-layerchromatographic silica gel was refluxed in hydrochloric acid to prepare activated silica gel.The particle size of silica gel was significantly reduced by the activation, as confirmed byscanning electron microscopy measurements. Electrochemical responses of K3[Fe(CN)6]indicated that activated silica gel was capable of facilitating electron transfer and increasingsurface area.2. Highly-sensitive electrochemical method for the detection of quercetin.Electrochemical behaviors of quercetin on carbon paste electrode (CPE), silicagel-modified CPE and activated silica gel-modified CPE were detailedly studied. Silicagel-modified CPE gave rise to a higher signal responding to quercetin oxidation relative tounmodified CPE, while a further enhancement of oxidation peak current was observed onactivated silica gel-modified CPE. Therefore, activated silica gel exhibited moreremarkable enhancement effect toward the oxidation of quercetin. The further investigationof the oxidation mechanism showed that the oxidation of quercetin involved two electronsand two protons process, which occurred at the positions of two phenolic hydroxyl groups.The influences of pH value, amount of activated silica gel, accumulation potential and timeon the signal enhancement of quercetin were examined, and a novel electrochemicalmethod was successfully developed for the detection of quercetin. The linear ranger wasfrom5to100g L-1, and the limit of detection was3.53g L-1. Finally, this methodologywas successfully applied in the test of honeysuckle and tea samples.3. Highly-sensitive electrochemical method for the detection of protocatechuicaldehyde. Electrochemical behaviors of protocatechuic aldehyde on CPE, silica gel-modifeid CPE and activated silica gel-modified CPE were systematically investigatedin the presence of CTAB with different concentrations. The results showed that activatedsilica gel and CTAB displayed synergistic effects on the oxidation of protocatechuicaldehyde, and greatly increased the detection sensitivity of protocatechuic aldehyde.Experiment parameters were further optimized, and a novel electrochemical method wasestablished for the detection of protocatechuic aldehyde. The linear range was from5to1000g L-1, and the limit of detection was2.51g L-1. At last, this new method wassuccessfully used to detect protocatechuic aldehyde in Xiangdan injection samples.