title: Enantioseparation and stacking of Cyanobenz[f]isoindole-amino acids by reverse polarity capillary electrophoresis and sulfated beta-cyclodextrin.
abstract: A capillary electrophoresis method with laser-induced fluorescence detection for the chiral separation of cyanobenz[f]isoindole (CBI) derivatives of amino acids was developed and optimized. The enantioseparations are accomplished with sulfated beta-CD (S-beta-CD) as chiral selector at low pH and reverse polarity. BGE conditions were optimized for CBI-serine and then applied to other CBI-amino acids. Baseline resolution of 13 CBI-amino acids was achieved using a single BGE formulation of 2 wt % S-beta-CD in 25 mM phosphate buffer at pH 2.00 and a voltage of -30 kV. pH is the most critical BGE parameter affecting resolution. At 2 wt % S-beta-CD, CBI-serine enantiomers are baseline-resolved at pH 2.00 but no resolution is obtained at pH 3.00. l-Glutamate, l-aspartate and d-serine are simultaneously quantified in the microdialysate of an arctic ground squirrel to illustrate the application to biological samples. Dilute solutions of the CBI-amino acids in water can be stacked by hydrodynamic injection with a 100-fold improvement in signal-to-noise ratio without loss of chiral resolution. The stacking is proposed to consist of field-amplified migration, pH-mediated stacking, and sweeping by S-beta-CD. The limit of detections for CBI-dl-serine and CBI-dl-glutamate are determined as 0.20 and 0.30 nM, respectively. The stacking method was not applicable to the high ionic strength microdialysates.
authors.affiliation: Department of Chemistry & Biochemistry, Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, Alaska 99775, USA.
authors.forename: Daniel L
authors.initials: DL
authors.lastname: Kirschner
authors.forename: Michael
authors.initials: M
authors.lastname: Jaramillo
authors.forename: Thomas K
authors.initials: TK
authors.lastname: Green
mesh_terms: D000596:Amino Acids / Q000032:analysis* / Q000302:isolation & purification; D000818:Animals; D001565:Benzoates / Q000737:chemistry; D019075:Electrophoresis, Capillary / Q000379:methods*; D005453:Fluorescence; D006624:Hippocampus / Q000737:chemistry; D007211:Indoles / Q000032:analysis* / Q000302:isolation & purification; D007834:Lasers; D012589:Sciuridae / Q000378:metabolism; D013050:Spectrometry, Fluorescence; D013237:Stereoisomerism; D013431:Sulfates / Q000737:chemistry*; D047392:beta-Cyclodextrins / Q000737:chemistry*
chemical_list: D000596:Amino Acids; D001565:Benzoates; D007211:Indoles; D013431:Sulfates; D047392:beta-Cyclodextrins; C097383:4-cyanobenzoic acid; C031215:betadex