Quercetin (Qu) is one of the most abundant flavonoids in the human diet. High concentrations of Qu can easily cause adverse effects and induce inflammation, joint pain and stiffness. In this study, Heme was used as a sensitive element and deposited and formed nanorods on a glassy carbon electrode (GCE) for the detection of Qu. The Heme/GCE sensor was characterized using scanning electron microscopy (SEM), cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) techniques. Under optimized conditions, the developed sensor presented a linear concentration ranging from 0.1 to 700 μmol·L−1 according to the CV and DPV methods. The detection limit for the sensor was 0.134 μmol·L−1 and its sensitivity was 0.12 μA·μM−1·cm−2, which were obtained from CV analysis. Through DPV analysis we obtained a detection limit of 0.063 μmol·L−1 and a sensitivity of 0.09 μA·μM−1·cm−2. Finally, this sensor was used to detect the Qu concentration in loquat leaf powder extract, with recovery between 98.55–102.89% and total R.S.D. lower than 3.70%. The constructed electrochemical sensor showed good anti-interference, repeatability and stability, indicating that it is also usable for the rapid detection of Qu in actual samples.

Lysozyme (Lyz) is found in animal and human bodily fluids, and is frequently utilized as a biomarker for various diseases. Even trace amounts of Lyz in food can potentially trigger adverse immune system reactions in sensitive individuals. Therefore, it is very important to monitor Lyz concentration in foods for safety. In this study, a simple and convenient electrochemical sensor for Lyz detection was prepared by modifying gold nanoparticles (AuNPs) and ferrocene dicarboxylic acid (Fc(COOH)2) on a glass carbon electrode (GCE), which was characterized fully by various electrochemical methods and field emission scanning electron microscope (FESEM). The proposed method utilized Fc(COOH)2 as a probe and AuNPs as an electron transfer medium to improve the sensor’s current response performance. Under optimal conditions, the sensor was used to detect Lyz with a linear range from 0.10~0.70 mmol·L−1 with a sensitivity of 50.55 μA·mM−1·cm−2, and a limit of detection (LOD) of 0.07 mmol·L−1. In the standard addition experiment of food samples (egg white), a total R.S.D. of less than 6.75% and an average recovery between 95.45% and 102.62% were obtained.