A new electrochemical method for the detection of quercetin in onion, honey and green tea using Co3O4 modified GCE

Quercetin (Qu) is a most active biological flavonoid and it has a very wide spectrum of potential applications. Herein, we have synthesized ionic liquid assisted Co3O4 nanostructures through an aqueous chemical growth method and fabricated a Co3O4 modified GCE as an electrochemical sensor for the sensitive detection and determination of Qu. The proposed electrochemical sensor was not only prepared with a very easy, simple and cheap method but it was also found to be very selective, sensitive and highly stable for the detection of Qu in standard solutions as well as in real food samples like onion, honey and green tea. The prepared electrochemical sensor has shown an excellent electrochemical response for Qu with a wide range of detection from 0.01 to 3 µM. The oxidation current response of Qu on Co3O4 modified GCE was found 4 times higher than the response of bare GCE which is due to the high conductivity, tremendous catalytic ability and large surface area of Co3O4 nanostructures. The limit of detection (LOD) and the limit of quantification (LOQ) for Co3O4/GCE sensor was calculated and found to be 0.0002 µM and 0.0007 µM respectively. While, the amount of Qu in real samples was found to be 5.367 µg/mL in honey, 15.58 µg/g in onion and 3.473 mg/g in green tea respectively. In comparison to the previously reported sensors, the prepared Co3O4/GCE sensor has shown a higher electrocatalytic capability, remarkable stability, super sensitivity and adequate selectivity for the determination of Qu in standard solutions as well as in real samples.