The innovative concept for coupling of HPLC to a BDD electrode for the determination of alpha-lipoic acid in dietary supplements is reported. Particular effort was focused on the use of the BDD electrode as an alternative detector to overcome the drawback of using metal, GC or modified electrodes. With the superior electrochemical properties of the BDD electrode, it not only allows highly sensitive detection but also simplicity and cost-effectiveness due to the fact that -lipoic acid can be detected amperometrically
without derivatization or the use of a pulse waveform. Compared to other validated chromatographic methods, the total assay could be completed in a several-fold shorter time period and yet could successfully determine alpha-lipoic acid contents in dietary supplements without extraction or pre-concentration. Reproducible signals obtained with %RSD for intra- and inter-assay were in all cases below 5%. These results implied that a BDD detection exhibited a high reproducibility. Although, we have not tested BDD electrodes for long-term stability under continuous operation, they exhibited highly reproducible responses from day to day. Also, the response was reproducible after several days of exposure to the laboratory atmosphere. Indeed, the good agreement in the determination of alpha-lipoic acid concentrations in supplement samples by the developed method and the standard HPLC-UV method further vouches for the simplicity and straightforwardness of this technique. In conclusion, HPLC coupled with BDD amperometry provides an attractively alternative method for the determination of alpha-lipoic acid in food supplement samples, among others, andmay also be useful for biomedical and clinical investigation of alpha-lipoic acid levels.