Cyclodextrin modified

The data were collected using fluorescence measurements, which allow both identification and quantitation of the fluorophore in solvent extraction. Important experimental considerations such as solvent choice, temperature, and concentrations of the modifier and the analytes are discussed. The utility of this method as a means of simplifying complex PAH mixtures is also evaluated. In addition, the coupling of cyclodextrin-modified solvent extraction with luminescence measurements for qualitative evaluation of components in mixtures will be discussed briefly. 

Table II. Extraction Efficiencies (%) for Several PAHs using Cyclodextrin-Modified Extraction...

Cyclodextrin-modified solvent extraction has been used to extract several PAHs from ether to an aqueous phase. Data evaluation shows that the degree of extraction is related to the size of the potential guest molecule and that the method successfully separates simple binary mixtures in which one component does not complex strongly with CDx. The most useful application of cyclodextrin-modified solvent extraction is for the simplification of complex mixtures. The combined use of CDx modifier and data-analysis techniques may simplify the qualitative analysis of PAH mixtures. 

Nishi, H. and Matsuo, M., Separation of corticosteroids and aromatic hydrocarbons by cyclodextrin-modified micellar electrokinetic chromatography, J. Liq. Chromatogr., 14, 973, 1991. 

Lin et al. [95] used capillary electrophoresis with dual cyclodextrin systems for the enantiomer separation of miconazole. A cyclodextrin-modified micellar capillary electrophoretic method was developed using mixture of /i-cyclodextrins and mono-3-0-phenylcarbamoyl-/j-cyclodextrin as chiral additives for the chiral separation of miconazole with the dual cyclodextrins systems. The enantiomers were resolved using a running buffer of 50 mmol/L borate pH 9.5 containing 15 mmol/L jS-cyclodextrin and 15 mmol/L mono-3-<9-phcnylcarbamoyl-/j-cyclodextrin containing 50 mmol/L sodium dodecyl sulfate and 1 mol/L urea. A study of the respective influence of the /i-cyclodcxtrin and the mono-3-(9-phenylcarbamoyl-/i-cyclodextrin concentration was performed to determine the optical conditions with respect to the resolution. Good repeatability of the method was obtained. 

Figure 15.14 illustrates a typical voltammetric result for the determination of dopamine in the presence of ascorbic acid with a CNT-modified electrode. The selective voltammetric detection of uric acid [82] or norepinephrine [83] in the presence of ascorbic acid has been demonstrated with a (3-cyclodextrin-modified electrodes incorporating CNTs. Ye et al. [84] have studied the electrocatalytic oxidation of uric acid and ascorbic acid at a well-aligned CNT electrode, which can be used for the selective determination of uric acid in the presence of ascorbic acid. The simultaneous determination of dopamine and serotonin on a CNT-modified GC electrode has also been described [85],... 

Z. Wang, Y. Wang, and G. Luo, A selective voltammetric method for uric acid detection at (3-cyclodextrin modified electrode incorporating carbon nanotubes. Analyst 127, 1353-1358 (2002). 

Organolead and organoselenium compounds were separated satisfactorily by high-performance capillary electrophoresis, using /1-cyclodextrin-modified micellar electroki-netic chromatography with on-column UVV detector set at 210 nm130. 

In 1990, the applicability of cyclodextrin-modified MEKC (CD-MEKC) was successfully explored for the first time by adding a neutral CD to the micellar solution for the separation of highly hydrophobic and closely related compounds such as chlorinated benzene congeners, polychlorinated biphenyl (PCB) congeners, and tetrachlorodibenzo-p-dioxin (TCDD)... 

Lucangioli, S. E., Rodriguez, V. G., Otero, G. C. E, and Carducci, C. N. (1998). Determination of related impurities of bile acids in bulk drugs by cyclodextrin-modified micellar electrokinetic chromatography./. Capillary Electrophor. 5, 139-142. 

Chen, Z., Ozawa, H., Uchiyama, K., and Hobo, T. (2003). Cyclodextrin-modified monolithic columns for resolving dansyl amino acid enantiomers and positional isomers by capillary electrochromatography. Electrophoresis 24, 2550-2558. 

Otsuka, K., Smith, C. J., Grainger, J., Barr, J. R., Patterson, J., Tanaka, N., and Terabe, S. (1998). Stereoselective separation and detection of phenoxy acid herbicide enantiomers by cyclodextrin-modified capillary zone electrophoresis-electrospray ionization mass spectrometry. /. Chromatogr. A 817, 75-81. 

Cyclodextrines, modified with 2-cyanoethyl and with bis(2-cyanoethyl)amino groups were used as ligands in the [PdCy + [CuCU]-catalyzed Wacker-oxidation of 1-octene. Without the modified cyclodextrins the yield of 2-octanone was less than 1 %, which could be raised to 73 % by the addition of nitrile-modified P-cyclodextrin ligands (60 °C, 2 h). 

CL Copper, JB Davis, RO Cole, MJ Sepaniak. Separations of derivatized amino acid enantiomers by cyclodextrin-modified capillary electrophoresis Mechanistic and molecular modeling studies. Electrophoresis 15 785-792,... 

E Szoko, J Gyimesi, L Barcza, K Magyar. Determination of binding constants and the influence of methanol on the separation of drug enantiomers in cyclodextrin-modified capillary electrophoresis. J Chromatogr A 745 181-187,... 

CL Copper, MJ Sepaniak. Cyclodextrin-modified micellar electrokinetic capillary chromatography separations of benzopyrene isomers. Correlation with computationally derived host-guest energies. Anal Chem 66 147—154, 1994. 

A Aumatell, RJ Wells. Enantiomeric differentiation of a wide range of pharmacologically active substances by cyclodextrin-modified micellar electrokinetic capillary chromatography using a bile salt. J Chromatogr A 688 329—337, 1994. 

CL Cooper, JB Davis, MJ Sepaniak. Mechanisms of enantiomeric resolution in cyclodextrin-modified capillary electrophoretic separations of binaphthyl compounds. Chirality 7 401-408, 1995. 

MECC has also been reported to be an effective method for the separation of enantiomers [269, 270]. Tsai et al. [271] reported y-cyclodextrin-modified micellar capillary electrophoresis technique for the separation of dansylated-DL-amino acids. 

Memiolu, E., Bochot, A., Sen, M., Sharon, D., Duchene, D., Hincal, A.A. (2002). Amphiphilic p-cyclodextrins modified on the primary face synthesis, characterization and evaluation of their potential as novel excipients in the preparation of nanocapsules. Journal of Pharmaceutical Sciences, 91, 1214-1224. 

Tricyclic anti-depressive drugs Cyclodextrin-modified SPCE 0.196 pM 2.75 pM Serum (86-98) 0.04-0.5 pM Differential pulse voltammetry Ferancova et al. [133]... 

Fig. 3 Photoresponsive polymer surface sensitive to pH and light. Adsorption and release of cytochrome c triggered by pH (b, c, and d) release of the polymer layer and cytochrome c by breaking the host-guest interactions between surface-tethered azo dye and cyclodextrin via light irradiation (a and d). The molecular structure on the right represents the host-guest complexa-tion of the azo dye with the cyclodextrin-modified poly(acrylic acid). Reprinted, with permission, from [68]. Copyright (2009) Wiley Interscience...

Huq and Mercier191 synthesized cyclodextrin modified silicas by first coupling the cyclodextrin units to 3-aminopropyltriethoxysilane (APTES) and then subjecting it to a co-condensation reaction with TEOS (Fig. 3.15c). Interestingly, all attempts to anchor cyclodextrins by grafting onto previously thiol-functionalized silicas have been unsuccessful. It has also been demonstrated that the cyclodextrin units on the... 

Fig. 7.7. DRIFT spectrum of the inner wall of an etched cyclodextrin modified 50 m capillary.

Fig. 7.12. Electrochromatographic separation of the optical isomers of D,L-chlorodiazepoxide on an etched cyclodextrin modified capillary. pH = 3.0, V = 20 kV, L = 45 cm, 1 = 25 cm. Peaks 1 = impurity 2,3 = D,L isomers of chlorodiazepoxide (individual isomers not identified).

Enantiomer separation of various compounds such as barbituric acids, benzoin, MTH-proline, glutethimide, a-methyl-oc-phenyl-succinimide, y-phenyl-y-butyrolac-tone, methyl-mandelate, l-(2-naphthyl)ethanol, mecoprop methyl, diclofop methyl and fenoxaprop methyl by pressure supported CEC on a permethyl-P-cyclodextrin modified stationary phase was described by Wistuba and Schurig [42-44]. Three different separation beds were used (i) permethyl-P-cyclodextrin was covalently attached via a thioether to silica (Chira-Dex-silica) [42], permethyl-P-cyclodextrin was linked to a dimethylpolysiloxane and thermally immobilized (ii) on silica (Chirasil-Dex-silica) [43] or (iii) on a silica monolith (Chirasil-Dex-monolith) [44], respectively. 

Barbiturates Permethyl-(3-cyclodextrin-modified silica gel (Nucleosil, 5 pm) Methanol-5 mM phosphate buffer, pH 7.0 (1 4) 400 mm x 100 pm i.d. 235 mm effective length, chiral separation, pressure-supported CEC 139... 

Microsolvent effects in the cyclodextrin cavity have also been observed in hypochlorite chlorination of acetophenone1029. Higher para selectivity has been observed in the bromination of acetanilide and benzanilide in presence of cyclodextrins or amylose1030 and in the anodic chlorination of anisole with cyclodextrin-modified electrode1031. 

The FITC labeling method was also applied to chiral separations of amino acids on a microchip to determine the enantiomeric ratios of amino acids found on a meteorite [27], Since biotic amino acids are normally single enantiomers, chiral separations of amino acids are not truly clinical in nature, but illustrate the potential for chiral separations of small molecules of clinical interest. Ma-thies and co-workers used this technique to search for evidence of life in extraterrestrial environments. Enantiomeric forms of Val, Ala, Glu, and Asp could be discriminated by addition of a-, (3-, or y-cyclodextrin (CD) to the run buffer. Improved resolution with faster separations was found with respect to conventional CE. This method has been modified, by addition of SDS to the buffer, to perform cyclodextrin-modified micellar electrokinetic chromatography (CD-MEKC) [28]. Increasing the SDS concentration decreased the magnitude of elec-troosmotic flow (EOF), increasing the effective migration distance, and therefore the resolution on the microchips. 

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