Enantiomeric separation of amino acids derivatized with 7-fluoro-4-nitrobenzoxadiazole by capillary liquid chromatography/tandem mass spectrometry.
Pre-column derivatization allowed stacking amino acid enantiomers on C18 reversed-phase micro extraction columns, thus facilitating sample loading in capillary HPLC/tandem mass spectrometry. Two tagging reagents, i.e. 7-fluoro-4-nitrobenzoxadiazole (NBD-F) and 1-fluoro-2,4-dinitrobenzene (DNB-F) were evaluated. Both of them reacted readily with amino acids at an elevated temperature, resulting in derivatives that were effectively stacked and suitable for a sensitive MS/MS detection as well. Separation of the tagged enantiomers on a teicoplanin chiral stationary phase (CSP) with mobile phases compatible with MS detection was investigated. NBD-amino acid enantiomers (12 pairs) tested were all base-line resolved. However, the efforts to separate DNB-F tagged amino acid enantiomers on this CSP were not successful. Separation conditions including pH, organic modifiers, and column dimension were studied. All the NBD-amino acids studied could be sensitively detected by MS/MS detection set in the negative ion mode, but only a few including NBD-Asp, BND-Glu, NBD-Ser, and NBD-Thr were detected in the positive ion mode. Thus, the selectivity for enantiomeric determination of excitatory amino acids (e.g. Asp and Glu) was further improved by choosing MS/MS detection in the positive ion mode.
Song
Yaru
Y
Department of Chemistry, Jackson State University, 1400 J.R. Lynch Street, Jackson, MS 39217-0510, USA.
Shenwu
Ming
M
Zhao
Shulin
S
Hou
Dongyan
D
Liu
Yi-Ming
YM
D000596:Amino Acids / Q000032:analysis / Q000737:chemistry* / Q000302:isolation & purification*; D002853:Chromatography, Liquid; D004139:Dinitrofluorobenzene / Q000031:analogs & derivatives* / Q000737:chemistry; D013058:Mass Spectrometry; D010069:Oxadiazoles / Q000737:chemistry*; D013237:Stereoisomerism; D017334:Teicoplanin
C507646:7-fluoro-4-nitrobenzoxadiazole; D000596:Amino Acids; D010069:Oxadiazoles; D017334:Teicoplanin; D004139:Dinitrofluorobenzene