β-Cyclodextrin–ferrocene inclusion complex modified carbon paste electrode for amperometric determination of ascorbic acid

Inclusion complex of ferrocene (Fc) with β-cyclodextrin (β-CD) has been synthesized in ethylene glycol. It was unsolvable in water and had been successfully used to the preparation of β-CD–Fc inclusion complex modified carbon paste electrode (CFCPE). Solid paraffin was used as the binder of the electrode. Ascorbic acid (AA) was electrocatalytically oxidized at the electrode in NH3–NH4Cl buffer (pH 10.0) with a anodic peak potential of +0.20 V (vs. SCE). The anodic current was proportional to the concentration of AA in the range 1.0×10−3–5.0×10−7 mol l−1 with the detection limit of 1.0×10−7 mol l−1. Using the inclusion complex as the electroactive substance greatly increased the stability and reproducibility of CFCPE than using Fc; the lifetime of the electrode can be over 1 year. Because CFCPE responds rapidly and sensitively, it has been successfully applied to the determination of AA in fruit juices.