Electrochemical Sensing Platform Based on Carbon Dots for the Simultaneous Determination of Theophylline and Caffeine in Tea

A simple and selective method for the determination of caffeine (CAF) and theophylline(THEO) has been developed for a glassy carbon electrode (GCE) modified with a composite includingcarbon dots (CDs) and chitosan (CS). To our knowledge, there are no previous studies that analyzea CDs-modified GCE for the presence of CAF and THEO. The electrochemical behavior of a GCEmodified with a CDs-CS composite was studied in acidic medium by cyclic voltammetry (CV) anddifferential pulse voltammetry (DPV). Considering the sensor analytical parameters, the same linearconcentrations range was found for CAF and THEO ranging from 1 10?5 to 5 10?3 mol L?1with the same detection limit (LOD) of 1 10?6 mol L?1. The reproducibility and repeatabilitydata were satisfactory in terms of RSD%. Moreover, the storage stability was evaluated, evidencinggood results whatever the experimental conditions used. The developed sensor was applied for thesimultaneous determination of CAF and THEO in tea and drug, and results were compared withthose obtained with HPLC-ESI-MS in SIR mode as an independent method optimized on purpose.The electrochemical sensor presents the undoubled advantages in terms of cheapness, portability,and ease of use, since it does not require skilled personnel.