Xiong X, Li S F
Department of Chemistry, National University of Singapore, Singapore.
Electrophoresis. 1998 Sep;19(12):2243-51. doi: 10.1002/elps.1150191233.
The simultaneous separation and detection of small cations and anions by capillary zone electrophoresis (CZE) with indirect ultraviolet (UV) detection was successfully demonstrated in a background electrolyte (BGE) containing two UV-absorbing components. Benzylamine, imidazole, benzenesulfonic acid, sulfosalicylic acid, and pyromellitic acid were tested as the components of the BGE. The success of the simultaneous separation of the cations and anions is dependent upon the proper selection of the electrolyte components and control of the migration of the ions towards the detector. High pH is beneficial to the detection of anionic analytes but not to the separation of cationic analytes because of large electroosmotic flow produced under this condition. The upper pH limit of the working pH range is confined by the pKa value of the cationic component of the BGE. The influence of pH and total electrolyte concentration on the electroosmatic flow (EOF) counteracted each other. This counteraction effect imposes an upper limit on the change of total electrolyte concentration at certain pH. It was found that the EOF should be larger by at least 10 x 10(-5) cm2V(-1)s(-1) than the electrophoretic mobilities of the anions so that the anions could be detected on the cathodic side within reasonable times and with good peak shapes. In the imidazole-sulfosalicylic acid BGE, the detection limits (signal to noise, S/N = 3) for the cations and anions ranged from 100 to 900 ppb. In the benzylamine-pyromellitic acid BGE, K+, Na+, Li+, CH3 COO-, HPO4(2-), F-, ClO3-, ClO4-, NO3-, NO2-, Cl- and SO4(2-) were separated within twelve minutes. The strategies for selection of the electrolyte components of the binary BGE were also discussed.
通过毛细管区带电泳（CZE）结合间接紫外（UV）检测同时分离和检测小阳离子和阴离子，已在含有两种紫外吸收成分的背景电解质（BGE）中成功实现。测试了苄胺、咪唑、苯磺酸、磺基水杨酸和均苯四甲酸作为BGE的成分。阳离子和阴离子同时分离的成功取决于电解质成分的正确选择以及离子向检测器迁移的控制。高pH值有利于阴离子分析物的检测，但由于在此条件下产生较大的电渗流，不利于阳离子分析物的分离。工作pH范围的上限受BGE阳离子成分的pKa值限制。pH值和总电解质浓度对电渗流（EOF）的影响相互抵消。这种抵消作用对特定pH下总电解质浓度的变化施加了上限。发现EOF应至少比阴离子的电泳迁移率大10×10⁻⁵ cm²V⁻¹s⁻¹，以便阴离子能够在合理时间内且具有良好峰形的情况下在阴极侧被检测到。在咪唑 - 磺基水杨酸BGE中，阳离子和阴离子的检测限（信噪比，S/N = 3）范围为100至900 ppb。在苄胺 - 均苯四甲酸BGE中，K⁺、Na⁺、Li⁺、CH₃COO⁻、HPO₄²⁻、F⁻、ClO₃⁻、ClO₄⁻、NO₃⁻、NO₂⁻、Cl⁻和SO₄²⁻在十二分钟内被分离。还讨论了二元BGE电解质成分的选择策略。
