کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
1201545 1493629 2013 13 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Sweeping as a multistep enrichment process in micellar electrokinetic chromatography: The retention factor gradient effect
موضوعات مرتبط
مهندسی و علوم پایه شیمی شیمی آنالیزی یا شیمی تجزیه
پیش نمایش صفحه اول مقاله
Sweeping as a multistep enrichment process in micellar electrokinetic chromatography: The retention factor gradient effect
چکیده انگلیسی


• Assessment of sweeping efficiency is confirmed in the generalized case.
• RFGE is an additional focusing or defocusing step in the sweeping process.
• Final enrichment factor depends on retention factor of analyte in sample and in BGE.
• Equations accounting for the general case of sweeping with/without RFGE are derived.
• Enrichment factor and analyte solubility are greatly affected by pH of sample matrix.

The application of a new method developed for the assessment of sweeping efficiency in MEKC under homogeneous and inhomogeneous electric field conditions is extended to the general case, in which the distribution coefficient and the electric conductivity of the analyte in the sample zone and in the separation compartment are varied. As test analytes p-hydroxybenzoates (parabens), benzamide and some aromatic amines are studied under MEKC conditions with SDS as anionic surfactant. We show that in the general case – in contrast to the classical description – the obtainable enrichment factor is not only dependent on the retention factor of the analyte in the sample zone but also dependent on the retention factor in the background electrolyte (BGE). It is shown that in the general case sweeping is inherently a multistep focusing process. We describe an additional focusing/defocusing step (the retention factor gradient effect, RFGE) quantitatively by extending the classical equation employed for the description of the sweeping process with an additional focusing/defocusing factor. The validity of this equation is demonstrated experimentally (and theoretically) under variation of the organic solvent content (in the sample and/or the BGE), the type of organic solvent (in the sample and/or the BGE), the electric conductivity (in the sample), the pH (in the sample), and the concentration of surfactant (in the BGE). It is shown that very high enrichment factors can be obtained, if the pH in the sample zone makes possible to convert the analyte into a charged species that has a high distribution coefficient with respect to an oppositely charged micellar phase, while the pH in the BGE enables separation of the neutral species under moderate retention factor conditions.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of Chromatography A - Volume 1297, 5 July 2013, Pages 213–225
نویسندگان
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