Enantiomeric separation of d ‐ and l ‐serine using high‐performance liquid chromatography with electrochemical detection following pre‐column diastereomer derivatization

Enantiomeric separation of d ‐ and l ‐serine on an octadecylsilica column was investigated using (2 R )‐2,5‐dioxopyrrolidin‐1‐yl‐2,5,7,8‐tetramethyl‐6‐(tetrahydro‐2 H ‐pyran‐2‐yloxy)chroman‐2‐carboxylate ( R ‐NPCA), which was developed for a pre‐column derivatization reagent for electrochemical detection. In addition, (2 S )‐2,5‐dioxopyrrolidin‐1‐yl‐2,5,7,8‐tetramethyl‐6‐(tetrahydro‐2 H ‐pyran‐2‐yloxy)chroman‐2‐carboxylate ( S ‐NPCA) was newly synthesized from ( S )‐(−)‐6‐hydroxy‐2,5,7,8‐tetramethylchroman‐2‐carboxylic acid ( S ‐ α ‐CA), and the enantiomeric separation of d ‐ and l ‐serine using S ‐NPCA was also examined. The enantiomeric separation of d , l ‐serine was achieved using the R ‐ or S ‐NPCA as a chiral derivatization reagent, and the elution orders of the enantiomers were reversed between R ‐ and S ‐NPCA. The elution orders of d ‐ and l ‐serine unexpectedly reversed between the phosphate buffer at pH 4.0 and pH 2.2, both of which were used in the mobile phase. Separation factors obtained using R ‐ and S ‐NPCA were similar—1.09 and 1.07, respectively. The detection limit was approximately 940 fmol on the column (signal‐to‐noise ratio 3) when the applied voltage was +650 mV. Copyright © 2009 John Wiley & Sons, Ltd.