Rapid Analysis of Caffeine in Tea and Drink by Electrochemical Method

A rapid method for the determination of caffeine in tea and drink has been established. Cyclic voltammetry(CV), square wave voltammetry(SWV) and differential pulse voltammetry(DPV) were used to investigate the electrochemical behavior of caffeine at a glassy carbon electrode. The caffeine showed a sensitive oxidation peak at + 1.486 V using CV in a NaH2PO4-K2HPO4 buffer solution at pH 6.60. The impacts of buffer solution, pH, accumulation time and scan rate were discussed. The peak current was linear to caffeine concentration ranging from 2.0 × 10-6 to 2.0 × 10-3 mol/L with a detection limit of 3.0 × 10-7 mol/L by SWV, and ranging from 1.8 × 10-6 to 1.0 × 10-3 mol/L with a detection limit of 5.0 × 10-6 mol/L by DPV. In addition to satisfactory reproducibility and reversibility, the methods exhibited sufficient selectivity and thus were suitable for rapid determination of caffeine in tea and drink.