Institute of Chemical Methodologies, National Research Council, Area della Ricerca di Roma I, Via Salaria Km 29.300, 00015 Monterotondo Scalo (Rome), Italy.
J Chromatogr A. 2010 Jun 18;1217(25):4079-86. doi: 10.1016/j.chroma.2009.11.004. Epub 2009 Nov 10.
Capillary electrochromatography (CEC) was coupled with mass spectrometry (MS) for the separation of some selected pesticides and drug enantiomers. CEC separations were carried out in fused silica capillaries packed with either 5microm RP(18) silica or 5microm silica modified vancomycin particles. The capillary column was connected with the MS utilizing a laboratory-made liquid-junction interface equipped with a 50microm I.D. capillary-tip positioned at a few mm from the orifice of the MS. The CEC-MS set-up was operated without external pressure assistance during the electrochromatographic run commonly used to avoid bubble formation. However a hydrostatic pressure of a few kPa was applied only to the liquid-junction interface to optimize the ion-spray due to the low I.D. of the capillary-tip. In order to optimize the CEC-MS method, several experimental parameters were studied, namely the inlet pressure, the hydrostatic pressure into the liquid-junction interface, the type of sheath-liquid and the mobile phase. The application of an inlet pressure influenced only analyte retention times that were shortened by increasing the pressure. On the contrary the hydrostatic pressure applied to the interface increased the flow rate into the tip also increasing the ion-signal recorded in the mass spectrometry. The ion-signal raised almost linearly by increasing the outlet pressure till 3.5kPa and then decreased. The separation of the selected pesticides was not influenced at all changing the hydrostatic pressure on the interface. Some basic enantiomeric compounds of pharmaceutical interest were successfully separated by CEC achieving good resolution. They were detected by MS with limit of detection in a range of 0.24-0.60microg/mL.
毛细管电泳色谱（CEC）与质谱（MS）联用，用于分离一些选定的农药和药物对映异构体。在熔融石英毛细管中进行 CEC 分离，该毛细管中填充有 5μm RP（18）硅胶或 5μm 经万古霉素修饰的硅胶颗粒。毛细管柱通过实验室自制的带有 50μm ID 毛细管尖端的液体连接接口与 MS 连接，该尖端位于离 MS 喷口几毫米的位置。在电色谱运行过程中，CEC-MS 装置通常不使用外部压力辅助，以避免气泡形成，但会施加几 kPa 的静压仅施加到液体连接接口，以优化由于毛细管尖端的低 ID 而导致的离子喷雾。为了优化 CEC-MS 方法，研究了几个实验参数，即入口压力、液体连接接口中的静压、鞘液类型和流动相。入口压力的应用仅影响分析物的保留时间，通过增加压力缩短保留时间。相反，施加到接口的静压会增加进入尖端的流速，从而增加质谱中记录的离子信号。通过增加出口压力，离子信号几乎呈线性增加，直到 3.5kPa，然后下降。改变接口上的静压对所选农药的分离没有影响。通过 CEC 成功分离了一些具有药用价值的基本对映体化合物，实现了良好的分辨率。它们通过 MS 检测，检测限在 0.24-0.60μg/mL 范围内。
