Simultaneous determination of l- and d-lactic acid in plasma by capillary electrophoresis

A novel method for simultaneous determination of d- and l-lactic acids in plasma was presented by capillary electrophoresis with photodiode array detection at 195 nm. The separation was performed in an uncoated fused-silica capillary. The parameters influencing the resolution and the migration time of lactic acids were optimized. When 150 mM phosphate-Tris buffer (pH 7.0) consisting of 220 mM 2-hydroxypropyl-β-cyclodextrin and 0.2 mM tetradecyltrimethylammonium bromide was utilized as the running buffer, highly effective chiral separation of d- and l-lactic acids was achieved at about 42 min at an effective voltage of −25 kV. The resolution of lactic acid enantiomers was ≥1.25. The limits of detection of d- and l-lactic acids in standard solution without any pretreatment were 80 and 50 μM (S/N = 3), respectively. Sample pretreatment was preceded by protein-removal procedure with acetonitrile. With a pre-concentration procedure by 10 times, the limits of detection of d- and l-lactic acids were 20 and 15 μM (S/N = 10), respectively. The satisfactory analytical performance of the proposed method was validated.