Gold nanoparticle-graphene quantum dots nanozyme for the wide range and sensitive electrochemical determination of quercetin in plasma droplets.

A gold nanoparticle/graphene quantum dots (AuNP/GQD) nanozyme-modified screen-printed carbon electrode (SPCE) was developed for fast and ultrasensitive determination of quercetin by square-wave voltammetry. The nanosensing device was inserted in miniaturized equipment. Under the optimal experimental conditions, a good linear relationship between oxidation peak current and concentration of quercetin within a very wide range of 1.0 × 10-10 to 1.0 × 10-3 mol L-1 was obtained, with a very low limit of detection of 3.3 × 10-11 mol L-1. To prove the performance of the method, the reproducibility was evaluated and the RSD values were lower than 5.3% and 5.1% for the intra-day and inter-day measurements, respectively. The method was applied to the sensitive determination of quercetin in human plasma droplets with recovery rates of 92.6 to 101.7%.Graphical abstract.