Tailoring the Electrode by Cysteic Acid for Sensitive Determination of Adenine in Vitamin B4 Tablet

Cysteic acid, containing negatively charged sulfonic ligand, has been deliberately modified on the electrode by the electrochemical oxidation method. It could promote the accumulation of adenine on the electrode because of the electrostatic interaction between the negatively charged cysteic acid and the positively charged adenine at pH 6.0. After accumulation at the potential of 0.2 V for 300 s, adenine produced well-defined oxidation peaks at about +1000 mV. Cyclic voltammetric study indicated that the oxidation process was irreversible and adsoption-controlled. Based on the differential pulse voltammetric (DPV) procedure, the linear calibration curve for the detection of adenine over the range 2.0 x 10-7 -1.0 x 10-4 M was obtained. The detection limit (3σ) was down to 5.9 x 10-8 M. Such modified electrode was also successfully applied for the determination of adenine in Vitamin B4 tablet.