Micellar electrokinetic chromatography applications

Pomponio, R., Gotti, R., Hudaib, M., and Cavrini, V. 2002. Analysis of phenolic acids by micellar electrokinetic chromatography application of Echinacea purpurea plant extracts. J. Chromatogr. A 945, 239-247. 

The last set of experiments provides examples of the application of capillary electrophoresis. These experiments encompass a variety of different types of samples and include examples of capillary zone electrophoresis and micellar electrokinetic chromatography. 

A variety of formats and options for different types of applications are possible in CE, such as micellar electrokinetic chromatography (MEKC), isotachophoresis (ITP), and capillary gel electrophoresis (CGE). The main applications for CE concern biochemical applications, but CE can also be useful in pesticide methods. The main problem with CE for residue analysis of small molecules has been the low sensitivity of detection in the narrow capillary used in the separation. With the development of extended detection pathlengths and special optics, absorbance detection can give reasonably low detection limits in clean samples. However, complex samples can be very difficult to analyze using capillary electrophoresis/ultraviolet detection (CE/UV). CE with laser-induced fluorescence detection can provide an extraordinarily low LOQ, but the analytes must be fluorescent with excitation peaks at common laser wavelengths for this approach to work. Derivatization of the analytes with appropriate fluorescent labels may be possible, as is done in biochemical applications, but pesticide analysis has not been such an important application to utilize such an approach. 

Nishi, H. and Terabe, S., Application of micellar electrokinetic chromatography to pharmaceutical analysis, Electrophoresis, 11, 691, 1990. 

For many applications, diode array detection has become routine. A photodiode array was used for simultaneous detection of 100 capillaries in zone electrophoresis and micellar electrokinetic chromatography (MEKC).1516 Deflection of a laser beam by acoustic waves was reported as a means to scan six capillary channels on a microchip.17 The design of a low-noise amperometric detector for capillary electrophoresis has been reported.18... 

Dedicated applications of capillary zone electrophoresis (CZE) coupled to MS are discussed, particularly in the field of drug analysis. Development of other capillary-based electrodriven separation techniques such as non-aqueous capillary electrophoresis (NACE), micellar electrokinetic chromatography (MEKC), and capillary electrochromatography (CEC) hyphenated with MS are also treated. The successful coupling of these electromigration schemes with MS detection provides an efficient and sensitive analytical tool for the separation, quantitation, and identification of numerous pharmaceutical, biological, therapeutic, and environmental compounds. 

C Fujimoto. Application of linear solvation energy relationships to polymeric pseudostationary phases in micellar electrokinetic chromatography. Electrophoresis 22 1322-1329 (2001). 

RHH Neubert, Y Mrestani, M Schwarz, B Colin. Application of micellar electrokinetic chromatography for analyzing antiviral drugs in pharmaceutical semisolid formulations. J Pharm Biomed Anal 16 893-897, 1998. 

Although not used in any of the overall methods found, Fourier transform-infrared spectroscopy for detection after GC can supplement MS to verify the presence of DNOC in samples (Budzinski et al. 1992 Gurka et al. 1991 Schneider et al. 1991). Alternative separation methods have also been shown to be applicable to nitrophenols, including DNOC, but have not yet become routine. These methods include supercritical fluid chromatography (Ong et al. 1992 Pospisil et al. 1992), capillary zone electrophoresis (Chao and Whang 1994), and micellar electrokinetic chromatography (Ong et al. 1991). 

CRM for road dust (BCR-723) containing 81.3 2.5 Jg/kg Pt, 6.1 1.9 ig/ kg Pd, and 12.8 1.3 Jg/kg Rh, was introduced [49, 228]. It is widely used for quality control of results obtained in the analysis of environmental materials (e.g., airborne particulate matters, dusts, soils, and sediments). Comparison of results obtained using different analytical procedures and interlaboratory studies are recommended when there is a lack of suitable CRM (e.g., in examination of clinical samples). The use of standards based on real matrices (e.g., saliva, plasma, ultrafiltrates, and lung fluids) instead of synthetic solutions is recommended in such analyses. Difficulties with the identification and quantification of different metal species in examined samples make the reliability of results of great importance. The use of various instrumental techniques for examination of particular samples can be helpful. The application of chromatography, mass spectrometry, and electrochemistry [199] HPLC ICP MS and HPLC MS/MS [156] ESI MS and MALDI [162] micellar electrokinetic chromatography, NMR, and MS [167] AAS, ESI MS, and CD spectroscopy [179] SEC IC ICP MS and EC ESI MS [180] and NMR and HPLC [229] are examples of such approaches. 

Chromatographic and related electrophoretic methods for the separation of transition metal complexes or their ligands were reviewed . Micellar electrokinetic chromatography (MEKC) presents a new development in the field of capillary zone electrophoresis (CZE). The use of micellar solutions expands the application of CZE to electronically neutral solutes, as well as charged ones. Thus, electrically neutral / -diketonates Cr(dik)3, Co(dik)3, Rd(dik)3, Pt(dik)2 and Pd(dik)2 were separated by CZE in micellar solutions of sds. A linear log-log relationship was found between the distribution coefficient and the partition coefficient of the complex between dodecane and water, which was used for prediction of both the distribution coefficients and the migration times of different metal complexes . 

It is a detergent and wetting agent effective in both alkaline and acidic conditions. In recent years it has found application in analytical electrophoretic techniques SDS (sodium dodecyl sulfate) polyacrylamide gel electrophoresis is one of the more widely used techniques for the analysis of proteins and sodium lauryl sulfate has been used to enhance the selectivity of micellar electrokinetic chromatography (MEKC). ... 

Since micellar electrokinetic chromatography (MEKC) was hrst introduced in 1984, it has become one of major separation modes in capillary electrophoresis (CE), especially owing to its applicability to the separation of neutral compounds as well as charged ones. Chiral separation is one of the major objectives of CE, as well as MEKC, and a number of successful reports on enantiomer separations by CE and MEKC has been published. In chiral separations by MEKC, the following two modes are normally employed (a) MEKC using chiral micelles and (b) cyclodextrin (CD)-modilied MEKC (CD-MEKC ... 

Applications of the micellar electrokinetic chromatography (MEC) technique appear in Section V, dealing with... 

Capillary electrophoresis (CE) is a powerful separation technique. It is especially useful for separation of ionic compounds and chiral mixtures. Mass spectrometry has been coupled with CE to provide a powerful platform for separation and detection of complex mixtures such as combinatorial libraries. However, the full potential of CE in the application of routine analysis of samples has yet to be realized. This is in part due to perceived difficulty in the use of the CE technique compared to the more mature techniques of HPLC and even SFC. Dunayevskiy et al. [136] analyzed a library of 171 theoretically disubstituted xanthene derivatives with a CE/ESI-MS system. The method allowed the purity and makeup of the library to be determined 160 of the expected compounds were found to be present, and 12 side products were also detected in the mixture. Due to the ability of CE to separate analytes on the basis of charge, most of the xanthene derivatives could be resolved by simple CE-MS procedures even though 124 of the 171 theoretical compounds were isobaric with at least one other molecule in the mixture. Any remaining unresolved peaks were resolved by MS/MS experiments. The method shows promise for the analysis of small combinatorial libraries with fewer than 1000 components. Boutin et al. [137] used CE-MS along with NMR and MS/MS to characterize combinatorial peptide libraries that contain 3 variable positions. The CE-MS method was used to provide a rapid and routine method for initial assessment of the construction of the library. Simms et al. [138] developed a micellar electrokinetic chromatography method for the analysis of combinatorial libraries with an open-tube capillary and UV detection. The quick analysis time of the method made it suitable for the analysis of combinatorial library samples. CE-MS was also used in the analysis... 

Capillary electrophoresis (CE) has emerged as an efficient and rapid separation technique in recent years. Its high efficiency has been employed in many applications such as in the analysis of environmental pollutants.Different approaches have been adopted to enhance selectivity for the analysis of different types of compounds. There are two approaches most commonly used to improve CE separations the addition of modifiers into the electrophoretic medium and the modification of the column. Examples of the first approach include the addition of surfactants into the electrophoretic medium as in micellar electrokinetic chromatography (MEKC), and the use of organic solvents,cyclodextrines, " " or bile salts " as buffer modifiers. Examples of the second method include the use of gel-filled columns (capillary gel electrophoresis) " and the coating of the capillary wall surface. " " ... 

Some studies on the application of electrophoretic techniques to the separation of phthalate esters can be found in the literature.In these cases, micellar electrokinetic chromatography (MEKC) allowed the study of the migration of phthalate esters in different electrophoretic media. 

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