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A systematic approach to the elimination of co-detection between oppositely charged analytes and applications of dual-opposite injection capillary
Dissertation   Open access

A systematic approach to the elimination of co-detection between oppositely charged analytes and applications of dual-opposite injection capillary

Donna Marie Blackney
Doctor of Philosophy (Ph.D.), Drexel University
May 2016
DOI:
https://doi.org/10.17918/etd-6783
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Abstract

Chemistry Capillary electrophoresis Drugs--Analysis
Dual- opposite injection capillary zone electrophoresis (DOI-CZE) is a separation technique that utilizes both ends of the capillary for sample introduction and a suppressed electroosmotic flow (EOF) to simultaneously separate analytes of opposite charge. In any experiment, precision is the key to reliable results in quantitative measurements. In Chapter 2, the first detailed study of precision between CZE and DOI-CZE experiments was investigated. Data for each technique was evaluated based on the precision of migration time, corrected area, and resolution. As many separation parameters as possible were kept the same or similar in order to facilitate a fair comparison. The ability of DOI-CZE to simultaneously separate oppositely charged active ingredients in an over-the-counter pharmaceutical drug is demonstrated in Chapter 3. Representative electropherograms from a separation of Advil(r) Allergy & Congestion Relief tablets are shown. Each tablet analyzed contains a 200 mg ibuprofen, 10 mg phenylephrine and 4 mg chlorpheniramine. Due to the large difference in the active ingredient amounts between the analytes of interest, quantitative analysis under conventional CZE conditions would be more difficult than under the proposed DOI-CZE method. In DOI-CZE, a given charge of analytes can be subjected to appropriate amounts of pressure and time of injection while allowing analytes of opposite charge to utilize a different set of injection conditions. This can allow more representative concentrations of each active ingredient to be introduced into the capillary. Validation of each separation technique was investigated and the resulting data are described. Depending on the individual electrophoretic mobilities of the analytes of interest and the effective length that each analyte travels to the detection window, the elution order of analytes in a DOI-CZE separation can vary widely. One consequence of a variable elution order is that co-detection of oppositely charged analytes becomes possible under certain experimental conditions. While several approaches currently exist to avoid co-detection, they are often time consuming and inefficient. Chapter 4 describes a systematic approach to easily avoid co-detection by analyzing the net mobilities of the analytes of interest to aid in choosing appropriate capillary lengths for a particular separation. Simulated electropherograms that highlight various aspects of this new approach are shown. An electropherogram from the literature is replicated and the derived relationship is applied to show the potential advantages of this new technique.

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