Electrochemical Determination of Vitamin D3 in Pharmaceutical Products by Using Boron Doped Diamond Electrode

A sensitive square-wave voltammetry method was developed to determine cholecalciferol (vitamin D-3) in pharmaceutical products at boron-doped diamond electrode as a working electrode. Vitamin D-3 provided a well-defined voltammetric peak at around +1.00 V (vs. Ag/AgCl, 3.5 mol dm(-3)) in 0.02 mol dm(-3) Britton-Robinson buffer pH 5.0 prepared in 50 % ethanol. The influence of various factors such as type and pH of the supporting electrolyte, scan rate and square-wave parameters were studied and optimized. Under optimum conditions, the oxidation peak current increased linearly with the concentration of vitamin D-3 over the range of 2 to 200 mu mol dm(-3). The calculated limit of detection and limit of quantitation were 0.17 mu mol dm(-3) and 0.51 mu mol dm(-3), respectively. The boron-doped diamond electrode exhibited specific recognition capability for cholecalciferol amongst possible interferences, and the determination of vitamin D-3 was possible in samples such as commercial pharmaceutical products without complicated sample pretreatments.