De Cock Bart, Dejaegher Bieke, Stiens Johan, Mangelings Debby, Vander Heyden Yvan
Department of Analytical Chemistry and Pharmaceutical Technology, Center for Pharmaceutical Research, Vrije Universiteit Brussel, Laarbeeklaan 103, B-1090 Brussels, Belgium.
Department of Analytical Chemistry and Pharmaceutical Technology, Center for Pharmaceutical Research, Vrije Universiteit Brussel, Laarbeeklaan 103, B-1090 Brussels, Belgium; Laboratory of Instrumental Analysis and Bioelectrochemistry, Institute of Pharmacy, Université Libre de Bruxelles, Boulevard du Triomphe accès 2, B-1050 Bruxelles, Belgium.
J Chromatogr A. 2014 Aug 1;1353:140-7. doi: 10.1016/j.chroma.2014.03.022. Epub 2014 Mar 13.
Capillary electrophoresis (CE) is an electrophoretic separation technique that was rapidly increasing in popularity some years ago and that led to high expectations. Because of their different separation mechanisms, CE and HPLC are alternative and complementary separation techniques. Chiral molecules can be directly separated with CE by simply adding a chiral selector to the running buffer solution, leading to flexible and cheap methods. Major drawbacks of capillary electrophoretic separation methods are, however, the lower precision compared to HLPC methods and a more problematic analytical method transfer. Both above stated disadvantages limit the generalized use of CE methods in the pharmaceutical industry. Multiple solutions have been suggested to improve the precision of CE methods. In this work the application of a constant current during the electrophoretic separation instead of the more commonly used application of a constant voltage was studied on two CE instruments with different cooling mechanisms. This was done in the context of optimizing method transfer conditions. A constant current may reduce the generation of heat in the capillary and the consequentially radial and axial temperature fluctuations that both negatively influence the precision of the peak areas, migration times and resolutions of a CE method. The repeatability and time-different intermediate precision of both electrophoretic separation modes were compared on two different CE instruments after a successful analytical method transfer. The chiral separations of three beta-blockers, propranolol, sotalol and betaxolol, were used as test cases. A constant current led to a general improvement of the repeatability and time-different intermediate precision of the relative Area Under the Curve of all three beta-blockers, while that of the migration times remained rather constant. It also led to more similar electropherograms than the application of a constant voltage.
毛细管电泳（CE）是一种电泳分离技术，几年前其受欢迎程度迅速上升，并引发了人们的高度期望。由于分离机制不同，CE和HPLC是替代且互补的分离技术。通过在运行缓冲溶液中简单添加手性选择剂，CE可直接分离手性分子，从而产生灵活且廉价的方法。然而，毛细管电泳分离方法的主要缺点是与HPLC方法相比精度较低，且分析方法转移更成问题。上述两个缺点限制了CE方法在制药行业的广泛应用。人们已提出多种解决方案来提高CE方法的精度。在这项工作中，在两台具有不同冷却机制的CE仪器上研究了在电泳分离过程中施加恒定电流而非更常用的恒定电压的情况。这是在优化方法转移条件的背景下进行的。恒定电流可减少毛细管中热量的产生以及随之而来的径向和轴向温度波动，这两者都会对CE方法的峰面积、迁移时间和分离度的精度产生负面影响。在成功进行分析方法转移后，在两台不同的CE仪器上比较了两种电泳分离模式的重复性和不同时间的中间精密度。使用三种β受体阻滞剂普萘洛尔、索他洛尔和倍他洛尔的手性分离作为测试案例。恒定电流使所有三种β受体阻滞剂曲线下相对面积的重复性和不同时间的中间精密度普遍提高，而迁移时间的重复性和中间精密度保持相当恒定。与施加恒定电压相比，它还能产生更相似的电泳图谱。
