Capillary electrophoresis , natural

Karger, B. L., High performance capillary electrophoresis, Nature, 339, 641, 1989. 

This chapter will first cover the nature of electrophoretic separations, especially those concerning capillary electrophoresis. Comprehensive multidimensional separations will then be defined, specifically in terms of orthogonality and resolution. The history of planar and non-comprehensive electrodriven separations will then be discussed. True comprehensive multidimensional separations involving chromatography and capillary electrophoresis will be described next. Finally, the future directions of these multidimensional techniques will be outlined. 

Watanabe, T. and Terabe, S., Analysis of natural food pigments by capillary electrophoresis, J. Chromatogr. A, 880, 311, 2000. 

Carmine extracted from cochineal insects is one of the most used natural colorings for beverages and other foods. Some representative articles refer to isolation and spectrometric analysis or the use of HPLC or capillary electrophoresis (CE) to separate and characterize all cochineal pigments. Its active ingredient, carminic acid, was quantified by rapid HPLC-DAD or fluorescence spectrometry. Carminic acid, used as an additive in milk beverages, was separated within 9 min using a high-efficiency CE separation at pH 10.0 after a previous polyamide column solid phase extraction (SPE), ... 

At present, the most promising methods for synthetic colorant analysis seem to be those based on separation approaches such as HPLC and capillary electrophoresis (CE). CE is the method of choice for the determination of synthetic dyes in biological materials while HPLC is generally a more suitable method for the identification and determination of hydrophobic natural pigments, having a better sensitivity and efficiency than CE. 

Characterization of Organic Natural Dyes by Electrospray Mass Spectrometry Coupled with HPLC and/or Capillary Electrophoresis... 

Identification and quantification of natural dyes need high performance analytical techniques, appropriate for the analysis of materials of complicated matrices containing a small amount of coloured substances. This requirement perfectly fits coupling of modern separation modules (usually high performance liquid chromatography in reversed phase mode, RPLC, but also capillary electrophoresis, CE) with selective detection units (mainly mass spectrometer). 

M. Trojanowicz, L. Wojcik and K. Urbaniak Walczak, Identification of natural dyes in historical Coptic textiles by capillary electrophoresis with diode array detection, Chem. Anal. (Warsaw), 48, 607 620 (2003). 

M. Puchalska, M. Orlinska, M.A. Ackacha, K. Polec Pawlak and M. Jarosz, Identification of anthraquinone coloring matters in natural red dyes by electrospray mass spectrometry coupled to capillary electrophoresis, J. Mass Spectrom., 38, 1252 1258 (2003). 

Huck WC, Stecher G, Scherz H and Bonn G. 2005. Analysis of drugs, natural and bioactive compounds containing phenolic groups by capillary electrophoresis coupled to mass spectrometry. Electrophoresis 26(7-8) 1319-1333. 

Anions and uncharged analytes tend to spend more time in the buffered solution and as a result their movement relates to this. While these are useful generalizations, various factors contribute to the migration order of the analytes. These include the anionic or cationic nature of the surfactant, the influence of electroendosmosis, the properties of the buffer, the contributions of electrostatic versus hydrophobic interactions and the electrophoretic mobility of the native analyte. In addition, organic modifiers, e.g. methanol, acetonitrile and tetrahydrofuran are used to enhance separations and these increase the affinity of the more hydrophobic analytes for the liquid rather than the micellar phase. The effect of chirality of the analyte on its interaction with the micelles is utilized to separate enantiomers that either are already present in a sample or have been chemically produced. Such pre-capillary derivatization has been used to produce chiral amino acids for capillary electrophoresis. An alternative approach to chiral separations is the incorporation of additives such as cyclodextrins in the buffer solution. 

The various types of capillary electrophoresis are performed either in free solution or in gels. The choice of method depends on the nature of the sample and the analytical objective but capillary gel electrophoresis, including iso-electric focusing and SDS electrophoresis, is particularly useful for protein applications. 

Because of their high separation capacity, short analysis time, low reagent consumption and simplicity, various electrophoretic methods have found application in the separation and quantitative determination of anthocyanins in various complex matrices [267].The different techniques used for the measurement of anthocyanins in beverages [268], the application of capillary electrophoresis (CE) for the analysis of natural food pigments [269], the use of CE for the determination of anthocyanins in foods [270] and in medicinal plants [271] have been previously reviewed. 

The hyphenation of CE and NMR combines a powerful separation technique with an information-rich detection method. Although compared with LC-NMR, CE-NMR is still in its infancy it has the potential to impact a variety of applications in pharmaceutical, food chemistry, forensics, environmental, and natural products analysis because of the high information content and low sample requirements of this method [82-84]. In addition to standard capillary electrophoresis separations, two CE variants have become increasingly important in CE-NMR, capillary electrochromatography and capillary isotachophoresis, both of which will be described later in this section. 

Kniiver-Hopf, J., and Mohr, H. (1995). Differences between natural and recombinant interleukin-2 revealed by gel-electrophoresis and capillary electrophoresis. /. Chromatogr. A 717, 71—74. 

Ions are highly charged species by nature and lend themselves well to analysis by capillary electrophoresis (CE). In pharmaceutical analyses, we usually deal with small organic and inorganic anions and small cations or aliphatic amines. 

Owing to the polar and nonvolatile nature of most compounds used as medicinal drugs, reversed-phase HPLC is the most common technique for monitoring the dmg substance and its impurities. GC is also used, particularly for residual solvents, and capillary electrophoresis (CE) has been introduced in more recent times. Some older methods use thin-layer chromatography (TLC), but use of this methodology for the quantitative measurement of impurities is not common. 

S Sabbah, GKE Scriba. Separation of dipeptide and tripeptide enantiomers in capillary electrophoresis using carboxymethyl-beta-cyclodextrin and succinyl-beta-cyclodextrin. Influence of the amino acid sequence, nature of the cyclodextrin and pH. Electrophoresis 22 1385-1393, 2001. 

In liquid chromatography, affinity purification protocols (4-8) have been known for a long time. Naturally, electrophoresis can be used just as well to observe molecular or noncovalent interactions of DNA oligomers, provided the complex has distinct electrophoretic properties different from those of the free molecules. Therefore, affinity capillary electrophoresis (ACE) can be a powerful tool for studying DNA-drug or DNA-biopolymer interactions. Several reviews discussing these aspects of ACE have been published in recent years (9-19). The crucial aspects of DNA in this field are covered comprehensively in a recent overview article (20). 

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