Qualitative and Quantitative Analysis: Interpretation of Electropherograms
In this chapter the basic information on qualitative and quantitative analysis in CE is provided. Migration time and spectral data are described as the most important parameters used for identification of compounds. The parameters that negatively influenc
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Qualitative and Quantitative Analysis: Interpretation of Electropherograms Michał Szumski and Bogusław Buszewski
Abstract In this chapter the basic information on qualitative and quantitative analysis in CE is provided. Migration time and spectral data are described as the most important parameters used for identification of compounds. The parameters that negatively influence qualitative analysis are briefly mentioned. In the quantitative analysis section the external standard and internal standard calibration methods are described. Variables influencing peak height and peak area in capillary electrophoresis are briefly summarized. Also, a discussion on electrodisperssion and its influence on a observed peak shape is provided. Capillary electrophoresis, similar to chromatographic techniques, allows for identification of the separated analytes as well as for determination of their quantity in the analyzed sample [1, 2]. Qualitative and quantitative analysis protocols do not differ significantly from those used in chromatography. A migration time and such parameters as peak height or peak surface area are used. CE is also a comparative technique, which means that qualitative and quantitative data can be obtained from the comparison of the analyte peak parameters with the peak of a standard—for identification migration time can be used, and for quantitative analysis—the peak height and peak area.
4.1 Qualitative Analysis As mentioned above, capillary electrophoresis itself does not provide direct identification of a substance. A basic parameter used here is migration time (tM) of the analyte. Identification relies on a comparison of the migration time of a peak M. Szumski (&) B. Buszewski Faculty of Chemistry, Nicolaus Copernicus University, Torun´, Poland e-mail: [email protected]
B. Buszewski et al. (eds.), Electromigration Techniques, Springer Series in Chemical Physics 105, DOI: 10.1007/978-3-642-35043-6_4, Springer-Verlag Berlin Heidelberg 2013
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obtained for a standard with a migration time of a peak of unknown substance, assuming that both substances underwent electrophoresis under the same conditions. Of course, such comparison only allows the analyst to state with a high probability that unknown substance is identical with the standard. In the next step of identification data obtained from different detectors may be helpful. Diode array detectors (DAD) can take the spectrum in the range of UV–Vis (typically 190–800 nm). The shape of a given spectrum, characteristic minima and maxima, can allow for identification. The spectra of different substances can be gathered in a library (a set of spectra of standards, taken in specific conditions) to be used later by a CE software. The libraries can be purchased from different suppliers, however, they can also be self-made by analysts who possess high standards of purity. There is a serious drawback of the purchased libraries: most of them are dedicated to HPLC, so the spectra are probably taken in organic solvents. The advan
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