DIRECT COUPLING OF CAPILLARY ELECTROPHORESIS AND MASS SPECTROMETRY FOR HIGH SENSITIVITY DETECTION OF LOW MOLECULAR MASS COMPOUNDS

采用日立M-1000型四极杆质谱仪，采用大气压化学电离(APCI)和电喷雾电离(ESI)接口，建立了毛细管电泳质谱(CE)和电喷雾电离(MS)的直接联用方法。APCI接口由一个电喷雾器喷嘴、一个汽化器和一个带有电晕放电电极的化学电离室组成。在甲酸铵缓冲液(pH 3.0)中，用非离子表面活性剂毛细管电泳法分离亲缘关系密切的多肽。采用部分填充技术，在毛细管的一部分中填充双胶束溶液，以防止表面活性剂进入界面。采用水/甲醇/甲酸(50：50：1)混合溶液作为ESI界面的鞘液。结果：1.利用CE-ESI-MS成功分离检测了三个氨基酸残基不同的神经降压素类似物，并成功记录了这些多肽的MS谱图。以咖啡因为试品，探索了APCIMS的最佳操作条件。考察了鞘液流量(甲醇)、漂移电压和汽化器温度对咖啡因分子离子灵敏度的影响。漂移电压对灵敏度有显著影响。其他因素并不是很重要。在咖啡因溶液中添加离子表面活性剂不会降低灵敏度。

A Hitachi M-1000 quadrupole mass spectrometer equipped with atmospheric pressure chemical ionization (APCI) interface and electrospray ionization (ESI) interface was employed to develop a direct coupling method of capillary electrophoresis (CE) and mass spectrometry (MS). The APCI interface consisted of an electrospray nebulizer nozzle, a vaporizer and a chemical ionization chamber having a corona discharge electrode.1. The ESI interface was employed for the detection of closely related peptides, which were separated by CE using a nonionicsurfactant in an ammonium formate buffer (pH 3.0). The partialfilling technique where a part of the capillary was filled with amicellar solution was employed to prevent the surfactant from entering the interface. A mixture of water/methanol/formic acid (50 : 50 : 1) was employed as a sheath liquid of the ESI interface. Three neurotensin analogues different in one amino acid residue were successfully separated and detected by CE-ESI-MS and MS spectra of the peptides were successfully recorded.2. The optimum operating conditions of APCI-MS were explored using caffeine as a test sample. Effects of the flow rate of the sheath liquid (methanol), drift voltage, and vaporizer temperature on sensitivity were examined for the molecular ion of caffeine. The drift voltage affected significantly on sensitivity. Other factors were not very important. Addition of ionic surfactants to the caffeine solution did not deteriorate sensitivity.