By developing a novel chiral column, we integrate open tubular capillary electrochromatography into sheathless mass spectrometry (MS) for efficient analysis of underivatized amino acid enantiomers. The chiral column is easily fabricated by modifying the inner surface of a capillary with a three-dimensional porous layer (PL, thickness ∼ 90 nm, pore size ∼ 30 nm) and gold nanoparticles and by introducing a chiral selector, thiol β-cyclodextrin (SH-β-CD), onto the modified surface via Au–S bonds. This approach greatly enhances the specific surface area and thus the ratio of the stationary phase to mobile phase and interaction between the stationary phase and analytes. The proposed PLOT@Au@CD column is coupled to the sheathless CE-ESI-MS system for chiral analysis of amino acid enantiomers. No derivatization of amino acids is required for chiral analysis, and baseline separation of a total of 15 pairs of amino acid enantiomers is achieved within 17 min with high column efficiencies of 5.60 × 10⁴ to 1.82 × 10⁶ N/m, high resolutions of 1.51–10.0, and low limits of detection between 0.02 and 0.09 μg/mL. The separation efficiency and MS intensity are only slightly decreased over 60 runs or after usage for 15 days, showing excellent repeatability and stability of the PLOT@Au@CD column. The proposed method is successfully applied to the determination of amino acid enantiomers in vinegar samples with satisfactory accuracy. Our study provides a new approach for developing a chiral stationary phase in the chromatographic separation technique, which can be easily coupled to sensitive MS detection, thus it would be of value for various applications in the fields of chiral analysis.

中文翻译：

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开管毛细管电色谱-质谱法分析具有多孔层的非衍生氨基酸对映体-金纳米粒子修饰的手性柱

通过开发一种新型手性色谱柱，我们将开管毛细管电色谱法集成到无鞘质谱仪 (MS) 中，以有效分析未衍生化的氨基酸对映异构体。通过用三维多孔层（PL，厚度约 90 nm，孔径约 30 nm）和金纳米颗粒修饰毛细管的内表面并引入手性选择剂硫醇 β-环糊精（ SH-β-CD)，通过 Au-S 键在改性表面上。这种方法大大提高了比表面积，从而提高了固定相与流动相的比例以及固定相与分析物之间的相互作用。所提出的 PLOT@Au@CD 色谱柱与无鞘 CE-ESI-MS 系统耦合，用于手性分析氨基酸对映异构体。⁴至 1.82 × 10 ⁶ N/m，1.51–10.0 的高分辨率和 0.02 至 0.09 μg/mL 的低检测限。在 60 次运行或使用 15 天后，分离效率和 MS 强度仅略有下降，表明 PLOT@Au@CD 色谱柱具有出色的重复性和稳定性。该方法成功应用于醋样品中氨基酸对映异构体的测定，准确度令人满意。我们的研究为在色谱分离技术中开发手性固定相提供了一种新方法，该方法可以轻松地与灵敏的 MS 检测耦合，因此对于手性分析领域的各种应用具有价值。