Enantioseparation and Stacking of Cyanobenz[<i>f</i>]isoindole-Amino Acids by Reverse Polarity Capillary Electrophoresis and Sulfated β-Cyclodextrin
作者:Daniel L. Kirschner、Michael Jaramillo、Thomas K. Green
DOI:10.1021/ac061725+
日期:2007.1.1
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 β-CD (S-β-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-β-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-β-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-β-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.
开发并优化了一种采用激光诱导荧光检测的毛细管电泳方法,用于手性分离氨基酸的氰基苯并[f]异吲哚 (CBI) 衍生物。使用硫酸化 β-CD (S-β-CD) 作为手性选择剂,在低 pH 和反极性下完成对映体分离。 BGE 条件针对 CBI-丝氨酸进行了优化,然后应用于其他 CBI-氨基酸。使用单一 BGE 配方(含 2 wt% S-β-CD)在 25 mM 磷酸盐缓冲液中(pH 2.00)和 -30 kV 电压实现 13 个 CBI-氨基酸的基线分辨率。 pH 值是影响分辨率的最关键的 BGE 参数。当 S-β-CD 含量为 2 wt% 时,CBI-丝氨酸对映体在 pH 2.00 下可实现基线分离,但在 pH 3.00 下未获得分离。同时定量北极地松鼠微透析液中的 L-谷氨酸、L-天冬氨酸和 d-丝氨酸,以说明其在生物样品中的应用。 CBI-氨基酸在水中的稀溶液可以通过流体动力注射进行堆叠,信噪比提高了 100 倍,且不损失手性分辨率。建议堆叠由场放大迁移、pH 介导的堆叠和 S-β-CD 扫描组成。 CBI-dl-丝氨酸和CBI-dl-谷氨酸的检测限分别确定为0.20 和0.30 nM。堆积方法不适用于高离子强度微透析液。