title: Simultaneous determination of the endogenous free α-lipoic acid and dihydrolipoic acid in human plasma and erythrocytes by RP-HPLC coupled with electrochemical detector.
abstract: A highly sensitive, precise, and accurate reversed-phase high performance liquid-chromatography/electrochemical detection method for simultaneous determination of the endogenous free α-lipoic acid and dihydrolipoic acid in biological matrices is presented. The two analytes are extracted from samples with acetonitrile-10% m-phosphoric acid solution(aqueous) (50:50 v/v). To determine the total lipoic acid, samples are treated with tris(2-carboxyethyl)phosphine solution in phosphate buffer: pH 2.5 with 85% o-phosphoric acid prior to deproteination. The two analytes are separated on a C18 (150 × 4.6 mm, 5 μm) analytical column using acetonitrile-50 mM phosphate buffer: pH 2.5 with 85% o-phosphoric acid (35:65 v/v) as the isocratic mobile phase pumped at a flow rate of 2.0 ml/min at the column oven temperature of 35 °C. The column eluents are monitored at a potential of 0.9 V. These analytes are efficiently resolved in <7 min.
authors.affiliation: Department of Pharmacy, University of Peshawar, Peshawar, Pakistan, imrankhan@upesh.edu.pk.
authors.forename: Muhammad Imran
authors.initials: MI
authors.lastname: Khan
authors.forename: Zafar
authors.initials: Z
authors.lastname: Iqbal
authors.forename: Abad
authors.initials: A
authors.lastname: Khan
mesh_terms: D002138:Calibration; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D056148:Chromatography, Reverse-Phase / Q000379:methods*; D055664:Electrochemical Techniques / Q000295:instrumentation*; D004912:Erythrocytes / Q000378:metabolism*; D006801:Humans; D057446:Hydrodynamics; D012015:Reference Standards; D015203:Reproducibility of Results; D012996:Solutions; D012997:Solvents; D013048:Specimen Handling; D008063:Thioctic Acid / Q000031:analogs & derivatives* / Q000097:blood*
chemical_list: D012996:Solutions; D012997:Solvents; D008063:Thioctic Acid; C015144:dihydrolipoic acid