Abstract:

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．

Key words: caffeine, cyclic voltammetry, differential pulse voltammetry, square wave voltammetry, glassy carbon electrode