The development of a column-switching high-performance liquid chromatograph system for chiral separation of mouse urinary D, L-Lactate

Two high-performance liquid chromatograph (HPLC) systems with a Rheodyne Model 7000 switching valve for separation of D- and L-lactate in biological samples has been reported. However, since the switching valve was rotated manually, so that only 10 samples could be determined within one day. For better efficiency, a circuit for rotating the switching valve automatically, which is including mechanical units of motion, two timers, and electronic control units was designed. Total (D+L)-lactate fluorescent derivatives was separated from others by a TSKgel ODS-80Ts column, when the peak of lactate derivatives appeared in the chromatogram on the ODS column, the valve position was changed by switching and then the isolated lactate derivatives was introduced into the chiral column automatically. Then the D- and L- enantiomers were separated by the chiral column. The utility of the analyzer system was tested for the determination of chiral separation of urinary D, L-lactate in the mouse. It takes about 90 min to analyze one urine sample for a circulation. Before automation, we must turn the switching valve manually when the signal shows up, so that there must be someone always standby and only about 10 samples could be analyzed within one day. With the designed automatic column-switching HPLC system, the switching valve can be automatically turned at the setting time repeatedly and over 15 samples could be determined within one day. The automatic system makes the analysis of D-lactate be timesaving, convenient and reproducible.