Capillary electrophoresis definition

As a result of the pharmacopoeial harmonization process, general chapter 2.2.47. of the Ph.Eur. and general chapter 8 of the JP (Capillary Electrophoresis) and general chapter < 1047) of the USP (Biotechnology-Derived Articles — Tests, Capillary Electrophoresis ) have been harmonized to a major extent. At present some minor differences exist between the text and a few equations in the pharmacopoeia. In these chapters, the following definition of CE is given ... 

Knowledge of the pKa value is crucial for analyzing both lipophilicity and solubility of ionizable compounds, as discussed above. Ionization equilibria also affect several toxicokinetic parameters, such as intestinal absorption, membrane permeability, protein binding, and metabolic transformations. Therefore, much research has been invested in developing both experimental and computational tools for pKa determination. Experimentally, two high-throughput methods exist spectral gradient analysis and capillary electrophoresis. However, the most definitive methods are still... 

To determine dose (or assay) the quantity of the compound is assessed in the most specific way by HPLC or specific capillary electrophoresis methods using authenticated reference/working standards for quantitative evaluation are suitable for many products. In the case of viral or cell therapy, total protein determination or number of viable particles or (specific) cells might be appropriate dose definitions. In addition, DNA hybridization assays or the determination of total DNA can be applied. Alternatively, for some products a dose definition may be based on the potency of the applied amount. 

The operating definition of resolution in capillary electrophoresis is the same as that for chromatography (section 1.6.1). It is equal to the separation between two peaks divided by the average of their widths at base... 

While polyelectrolyte behavior is generally not within the remit of this work, Stellwagen, et a/. s use of capillary electrophoresis to examine a fundamental physico-chemical issue is worthy of note(49). Their interest was a vexing question, namely whether or not zwitterions contribute to the ionic strength / of a solution. Many would assert that the theoretical studies of Kirkwood are substantially definitive, but some doubts remain(50,51). Stellwagen, etal. noted that the Debye-Hueckel-Onsager electrophoretic theory requires pi [Pg.57]

Capillary electrophoresis (CE) is a separation technique for ionic or ionizable compounds. CE is particularly attractive because the instrumentation is inexpensive and separations are quick and efficient. As with GC and LC, CE can be coupled to and flame photometric detection (FED) to detect alkylphosphonic acids [30-32]. Indirect UV absorbance detection with CE has also been used for the analysis of nerve agents and their degradation products [33]. In an attempt to meet the demands of portable and efficient field instruments, miniaturized analytical systems with CE microchips have also been made for the separation and detection of alkylphosphonic nerve agents [34]. The aforementioned CE procedures all provide rapid identification without extensive sample preparation. CE is most likely to be used as a guide in order to select the appropriate methods for further analysis by more definitive techniques such as GC-MS, as most of the products detected and analysed are degradation products [35]. A review depicting various CE separation techniques, lab-on-a-chip technology and detection limits has been compiled by Pumera and is shown in Table 3.1. 

In addition to polymeric support media, capillaries and flowing buffers have been used as support media for electrophoresis. Although these are not used as frequendy, there are definite advantages for certain types of samples and appHcations. 

Sometimes other variables must be investigated such as the pH and/or the ionic strength of the buffer in the mobile phase or the concentration of additives in the mobile phase such as for instance tensio-active substances in micellar chromatography. In such a case the first step in an optimization is to screen these factors and to identify the most important ones for the subsequent optimization. The screening (Section 6.4.2) leads to a definition of the experimental domain in which the optimum is probably situated. This is somewhat similar to the retention optimization step. It is followed by an optimization step (Sections 6.4 and 6.7), in which the most important variables are changed, often according to an experimental design. Similar methods are used in capillary zone electrophoresis. 

Capillary zone electrophoresis (CZE) is an effective technique for the definitive verification of the chromatographic purity of the target compound because of the large number of theoretical plates obtainable. The advantages of CZE, such as the possibility of analyzing for relatively labile species because of the absence of chromatographic packing, must be... 

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