Department of Chemistry, Faculty of Science, Srinakharinwirot University, Sukumvit 23 Rd., Wattana, Bangkok 10110, Thailand.
J Chromatogr A. 2010 Dec 3;1217(49):7699-705. doi: 10.1016/j.chroma.2010.10.004. Epub 2010 Oct 13.
A fast liquid chromatographic separation, coupled with sensitive and straightforward detection using a boron-doped diamond (BDD) electrode, was developed and validated for the determination of α-lipoic acid in dietary supplement samples. The analysis was carried out using a reversed phase C18 (150 mm × 4.6 mm, 5 μm) column with a mobile phase consisting of a 1:1 (v/v) ratio of 0.05 M phosphate solution (pH 2.5):acetonitrile, at a flow rate of 1.0 mL/min. The detection potential obtained from hydrodynamic voltammetry was 1.05 V vs. Ag/AgCl. Under optimized conditions, the chromatographic separation was performed in less than 5 min, a good linear relationship was obtained between the current and the α-lipoic concentration within the range of 0.01-60 μg/mL (correlation coefficient of 0.9971), and a detection limit of 3.0 ng/mL was determined. Furthermore, this method was successfully applied to determine α-lipoic acid concentrations in selected commercial dietary supplement samples. The recovery of α-lipoic acid in spiked samples at 0.5, 5.0 and 30 μg/mL ranged from 94.4% to 103.6% with a relative standard deviation (RSD) of between 1.2% and 3.7%. In real samples, this developed methodology produced results that were highly correlated with the standard HPLC-UV approach. Therefore, the present method can be used for fast, selective and sensitive quantification of α-lipoic acid in dietary supplements.
建立并验证了一种快速液相色谱分离方法，结合使用硼掺杂金刚石（BDD）电极进行灵敏、直接的检测，用于测定膳食补充剂样品中的α-硫辛酸。分析采用反相 C18（150mm×4.6mm，5μm）柱，流动相由 0.05M 磷酸盐溶液（pH2.5）：乙腈（1:1，v/v）组成，流速为 1.0mL/min。通过动力学伏安法得到的检测电位为 1.05V 相对于 Ag/AgCl。在优化条件下，色谱分离在不到 5min 内完成，在 0.01-60μg/mL 范围内电流与α-硫辛酸浓度之间呈良好的线性关系（相关系数为 0.9971），检测限为 3.0ng/mL。此外，该方法成功应用于测定选定商业膳食补充剂样品中的α-硫辛酸浓度。在 0.5、5.0 和 30μg/mL 浓度下，α-硫辛酸的加标回收率在 94.4%至 103.6%之间，相对标准偏差（RSD）在 1.2%至 3.7%之间。在实际样品中，该方法与标准 HPLC-UV 方法具有高度相关性。因此，本方法可用于快速、选择性和灵敏地定量膳食补充剂中的α-硫辛酸。
