Establishment of a two-dimensional chiral HPLC system for the simultaneous detection of lactate and 3-hydroxybutyrate enantiomers in human clinical samples

A two-dimensional chiral high-performance liquid chromatography system was established for simultaneous detection of lactate (LA) and 3-hydroxybutyrate (3HB) enantiomers in human clinical samples. d-LA is increased upon kidney damage but 3HB protected against kidney injury. Therefore, determining the concentrations of d,. l-LA and d,. l-3HB simultaneously would be useful for evaluating pathological conditions. LA and 3HB were pre-column-derivatized with the fluorescent reagent 4-(. N-chloroformylmethyl-. N-methylamino)-7-nitro-2,1,3-benzoxadiazole (NBD-COCl) at 60. °C for 15. min and separated in the first dimension with a capillary monolithic octadecylsilane column. The mobile phase consisted of 13% acetonitrile and 0.05% tirfluoroacetic acid in water. Chiralpak QD-AX and KSAACSP-001S enantioselective columns were used in the second dimension to separate LA and 3HB enantiomers, respectively. Mobile phases were mixed solutions of methanol and acetonitrile containing formic acid. The separation factors were 1.14 and 1.08, respectively. The detection limit of LA and 3HB enantiomers was 10. fmol/injection. This method was applied to human clinical samples; intra- and inter-day relative standard deviations of LA and 3HB enantiomers were, respectively, 1.04-3.25% and 1.61-5.12% in plasma, 9.19-11.2% and 4.60-5.89% in urine, and 7.12-8.90% and 2.86-6.97% in saliva. This novel analytical method is a powerful tool for investigating variations in LA and 3HB enantiomers under disease conditions.