Optimum conditions for preparative operation of capillary zone electrophoresis

Abstract

Optimum conditions for preparative operation of capillary zone electrophoresisCifuentes, A.; Xu, X.; Kok, W.T.; Poppe, H. General rightsIt is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. AbstractThe possibilities to use capillary zone electrophoresis (CZE) as a preparative tool have been studied, mostly from a theoretical point of view. The preparative performance of CZE is quantitated by the production rate, the amount of analyte that can be purified per unit of time. The production rate available with CZE is shown to depend in the first place on the chemical characteristics of the analyte-buffer combination. A figure of merit can be defined for a buffer system, describing its susceptibility to analyte overloading. Methods to find an optimal bufer system are referred to. It is shown that the loadability of the system is inversely proportional to the plate number required for the separation.A second important factor for the maximum production rate is shown to be the thermal management of the instrumental system. The average increase of the solution temperature and the non-uniform migration velocity by temperature differences within the solutions are discussed. It is shown that in practical cases the temperature rise of the solutions will be the main limiting factor when high fields are used. With low fields, which in general give a higher production rate, siphoning of the solution becomes the dominant limitation for the production rate.With cylindrical capillaries the highest production rate that can be obtained under practical conditions is in the order of 5.10 -13 mol s -1. Experimental and theoretical results indicate that with rectangular capillaries the production rate can be increased by a factor of three.

Separations of enantiomers by preparative capillary isotachophoresis

“…For nonGaussian peak shapes the corresponding equations differ only in the numerical factors (other than H 2p) [16]. Under typical ITP and CZE separating conditions we can assume c (4) and (5) give:…”

“…Some basic relationships are defined in this section to form a frame for a comparison of ITP with commonly used preparative CZE [16]. Here, we assume the use of both techniques in the same capillary column.…”

“…(1), whereby the symbol for the electric field strength, E, is without the subscript to indicate a constancy of this parameter along the column. When we assume close migration velocities of the analyte in both techniques and at the same time typical ITP [26,27] and CZE [16,28] concentrations in its zones, then Eqs. (1) and (2) give the CZE/ITP ratio of the mass flows per unit time at the column outlet:…”

“…In this respect it is apparent that the total amount of the enantiomer(s) separable by a particular CE technique in a given column is a key performance parameter. Here, the production rate (the amount of the analyte separated per unit time) [16] may serve as a numerical parameter suitable for comparisons of different CE techniques. Requirements concerning chemical and enantiomeric purities of the enantiomer fraction(s) set additional performance criteria.…”

“…In CZE the production rate, n ,CZE , is given by the following equation [16]: Eqs. (7) and (8) give the production rate per unit cross section of the column as…”