Chiral pharmaceutical analysis techniques

Although industrial laboratories shied away from the technique at first, CE is now becoming more common in these labs for a variety of analyses, including ion analysis, chiral pharmaceutical analysis, and peptide mapping [1]. With the increased prevalence of CE in industrial analytical laboratories comes the need for instrument qualification to ensure the proper functioning and performance of the instrument in order to obtain consistent, reliable, and accurate data. 

Chiral separation of drng molecules and of their precursors, in the case of synthesis of enantiomerically pure drugs, is one of the important application areas of HPLC in pharmaceutical analysis. Besides HPLC, capillary electrophoresis (CE) is another technique of choice for chiral separations. Chapter 18 provides an overview of the different modes (e.g., direct and indirect ones) of obtaining a chiral separation in HPLC and CE. The direct approaches, i.e., those where the compound of interest is not derivatized prior to separation, are discussed in more detail since they are cnrrently the most frequently used techniques. These approaches require the use of the so-called chiral selectors to enable enantioselective recognition and enantiomeric separation. Many different molecnles have been nsed as chiral selectors, both in HPLC and CE. They can be classified into three different groups, based on their... 

In Table 1, the typical validation parameters required for the different types of analytical procedures are listed. For all these analytical procedures CE might be an appropriate analytical technique. In fact numerous validated CE methods for pharmaceutical analysis have been described in literature during the last decade.In Table 2, an overview is listed of the ICH validation parameters included in several reported CE validation studies. Since chiral purity determination is an important application area of CE methods, this test is listed separately as a specific analytical procedure. In addition, the determination of drug counterions has been included as a separate application. This overview illustrates that in general the required validation parameters are addressed in reported CE validation studies. It should be noted, however, that the validation parameters included in Table 2 are not necessarily evaluated exactly according ICH requirements in the reported references. Many pharmaceutical companies apply a phase-related validation approach in which the depth of validation depends on the clinical phase of development of the product involved. 

CE is an important separation technique within the field of pharmaceutical analysis. CE may be an attractive choice as analytical procedure for identification, assay, or (chiral) purity determination. In addition, CE may provide distinct advantages over existing pharmacopoeial... 

The first section of the book explores emerging novel aspects of HPLC and related separation methods based on the differential velocity of analytes in a liquid medium under the action of either an electric field (capillary electromigration techniques) or a gravitational field (field-flow fractionation). The section focusing on applications highlights four significant areas in which HPLC is successfully employed chiral pharmaceutical, environmental analysis, food analysis, and forensic science. 

In modem pharmaceutical laboratories, CE is still an important technique, but its application in pharmaceutical analysis is less widespread. The rapid developments in LC have to a greater extent overtaken CE techniques, hence the role of CE is either in niche applications such as chiral analysis or as an orthogonal analytical technique to HPLC. 

Solvent Extraction Principles. Forensic Sciences Drug Screening in Sport Systematic Drug Identification. Gas Chromatography Mass Spectrometry Chiral Separations. Immunoassays, Techniques Enzyme Immunoassays Luminescence Immunoassays. Liquid Chromatography Column Technology. Pharmaceutical Analysis Sample Preparation. 

CEC is considered a hybrid technique between HPLC and CE combining the high peak efficiency of CE with the high separation selectivity of multivariate stationary phases available in HPLC. The general applicability of CEC to the analysis of drugs including chiral separations has been demonstrated, but it has not yet been implemented in the arsenal of pharmaceutical analytical techniques. 

Health authorities worldwide have fixed purity requirements for active pharmaceutical ingredients (APIs). When applied to chiral drugs, this implies that, if one enantiomer is chosen to be developed and marketed as an API, the counterpart isomer will be considered an impurity. The rule affects new chemical entities (NCEs) and chiral dmgs previously commercialized as a racemic mixture chiral switches). Therefore, techniques to perform the analytical control of the enantiomeric composition, at any of the drug development steps, together with processes to produce enantiomeric compounds with the desired enantiomeric purity, are essential in this domain. Liquid chromatography using chiral stationary phases (CSPs) is applied at two levels, analysis and production of enantiomerically pure compounds. At present, it can be considered the most universal technique for enantiomer separation. 

Chiral Chromatography. Chiral chromatography is used for the analysis of enantiomers, most useful for separations of pharmaceuticals and biochemical compounds (see Biopolymers, analytical techniques). There are several types of chiral stationary phases those that use attractive interactions, metal ligands, inclusion complexes, and protein complexes. The separation of optical isomers has important ramifications, especially in biochemistry and pharmaceutical chemistry, where one form of a compound may be bioactive and the other inactive, inhibitory, or toxic. 

Enantiomeric separations have become increasingly important, especially in the pharmaceutical and agricultural industries as optical isomers often possess different biological properties. The analysis and preparation of a pure enantiomer usually involves its resolution from the antipode. Among all the chiral separation techniques, HPLC has proven to be the most convenient, reproducible and widely applicable method. Most of the HPLC methods employ a chiral selector as the chiral stationary phase (CSP). 

CE has been touted as a replacement for HPLC in the pharmaceutical industry. This was a shame, since the techniques are so different. For many measurements, it is an orthogonal technique to HPLC. Whereas HPLC separates based on interaction with the stationary phase, CE separates based on the ratio of charge to mass. There are numerous examples of where CE exceeds the resolving power of HPLC (e.g., ion analysis, chiral analysis, DNA quantification, separation, large molecule analysis, etc.). 

Amini, A. (2001). Recent developments in chiral capillary electrophoresis and applications of this technique to pharmaceutical and biomedical analysis. Electrophoresis 22(15), 3107-3130. 

Erny, G. L., and Cifuentes, A. (2006). Liquid separation techniques coupled with mass spectrometry for chiral analysis of pharmaceuticals compounds and their metabolites in biological fluids. ]. Pharm. Biomed. Anal. 40, 509—515. 

In common with all capillary-based techniques, modem GC offers high-efficiency separations, allowing analyte resolution even with relatively low selectivity differences. Flame ionisation is now the most common form of detection used for organic analytes in GC and is universal for hydrocarbon-containing species. Although achiral GC is used widely in the pharmaceutical industry for the analysis of residual solvents and volatile analytes, its apphcation to chiral analysis tends to be limited to chiral raw materials and smaller intermediates. As the mobile phase is a gas, only volatile analytes are applicable to analysis by GC, often precluding its use for the analysis of relatively large, complex API molecules. Moreover, analyte molecules also need to be thermally stable to the temperatures required to ensure volatilisation [114]. 

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