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  • 1
    Electronic Resource
    Electronic Resource
    Enantiomeric separations of remoxipride, propranolol, and trimipramine on CHIRAL-AGP using micellar chromatography and anionic additives (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 5 (1993), S. 224-228 
    Details
    ISSN: 0899-0042
    Keywords: chiral resolution ; hydrophobic amines ; α1-acid glycoprotein ; Tween® 20 ; anionic additives ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The retentions and enantiomeric resolutions of remoxipride, propranolol, and trimipramine were studied using a CHIRAL-AGP column with micellar mobile phases and aliphatic, anionic additives. The retentions of the compounds, which in neat buffer solution were very high (k′ 〉 50), could be decreased to k′ 〈 10 by adding a mixture of Tween® 20 and heptanoic acid to the mobile phase. The presence of the aliphatic acid was essential in order to increase the enantiomeric selectivity. An efficiency enhancement was obtained by increasing the temperature. With a mobile phase composition optimized for the separation of remoxipride, the possibility of detecting levels of the enantiomeric impurity (R-remoxipride) down to 0.025% in the drug was demonstrated. © 1993 Wiley-Liss, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530050406
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  • 2
    Electronic Resource
    Electronic Resource
    Retention model for the resolved enantiomers of felodipine on chiral-AGP using micellar mobile phases (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 23-27 
    Details
    ISSN: 0899-0042
    Keywords: felodipine ; retention model ; micellar mobile phases ; chiral resolution ; CHIRAL-AGP ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A retention model for the chiral separation of an uncharged solute, felodipine, on CHIRAL-AGP, using a micellar mobile phase is proposed. The model assumes the presence of two stereoselective sites and each enantiomer was found to interact with different sites. Addition of a chiral aliphatic alcohol, (+)-(S)-2-octanol, preferentially interacted with the binding site for (-)-(S)-felodipine. The monomeric form of the micellar agent (Tween® 20) competed with the enantiomers for the adsorption sites, and the formation of a 1:1 complex between the enantiomers and the micelles was assumed. The retention of the solutes was effectively controlled by adding small quantities (〈1.63 × 10-3 M) of the nonionic detergent Tween 20 to the mobile phase. Baseline separation was achieved by addition of 1.0 mM n-octylamine to the mobile phase; 8.14 × 10-4 M Tween 20 in phosphate buffer pH 7.0. The separation factor (α = 1.74) was unaffected by the detergent concentration in the presence of 1.0 mM n-octylamine. © 1995 Wiley-Liss, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530070105
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  • 3
    Electronic Resource
    Electronic Resource
    Microcolumns in pharmaceutical and biomedical research and development (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Microcolumn Separations 2 (1990), S. 164-165 
    Details
    ISSN: 1040-7685
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mcs.1220020402
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  • 4
    Electronic Resource
    Electronic Resource
    Response patterns with indirect UV detection in capillary zone electrophoresis (1998)
    Weinheim : Wiley-Blackwell
    Electrophoresis 19 (1998), S. 1683-1690 
    Details
    ISSN: 0173-0835
    Keywords: Capillary electrophoresis ; Indirect UV detection ; Response pattern ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Capillary zone electrophoresis with indirect UV-detection was used to separate mixtures containing both positively and negatively charged species. In order to understand the dependence of detector response patterns on the changes in compositions of the background electrolytes and the charge of marker ions (UV-absorbing ions), the separations were performed in two different systems. In a three-ion system (analyte ion, coion and counterion) a marker ion was the major ionic component of a buffer solution and in a two-coion or counterion system the marker ion was used as an additive. In the three-ion system the response profile of an analyte was in good agreement with the mathematical treatment based on the Kohlrausch regulation function. In the two-coion or counterion system the response patterns were more complicated; however, the experimental results agree well with data obtained from a computer simulation program. Peak directions of the analytes were not only determined by their relative charge to the marker ion, but were also associated with their relative mobilities to the buffer coion and the marker ion. The analytes with higher effective mobilities compared to the marker ion were detected as positive peaks and the ones with lower effectice mobilities as negative peaks. Similarly to the three-ion system, the detector response of an analyte was stronger by applying a marker coion compared to a counterion. An interesting result was obtained in the separation of a mixture of quaternary ammonium ions and sugars by using a cationic marker ion. The highest and most symmetrical peak was not a cation, but raffinose anion, which appeared most closely to the system peak. The observation suggests that the electromigration dispersion in its zone was eliminated by migrating close to the electroosmosis. A system peak with the mobility corresponding to the electroosmotic flow was obtained in both systems, and an additional system peak with a mobility close to that the marker ion was present in the systems using marker ions as additives.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.1150191027
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  • 5
    Electronic Resource
    Electronic Resource
    Capillary electroseparations of enkephalin-related peptides and protein kinase A peptide substrates (1995)
    Weinheim : Wiley-Blackwell
    Electrophoresis 16 (1995), S. 564-573 
    Details
    ISSN: 0173-0835
    Keywords: Capillary electrophoresis ; Micellar electrokinetic chromatography ; Mixed micelles ; Dynamic modification ; Reversed electroosmosis ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: The separations of enkephalin-related peptides and protein kinase A peptide substrates, with the common structural feature -Arg-Arg-X-Ser-Val-, were studied in micellar electrokinetic chromatography (MEKC) systems and compared with the capillary zone electrophoresis (CZE) mode. The influence of the magnitude and the direction of the electroosmotic flow on the selectivity was studied. Reversed electroosmosis was obtained by adding a hydrophobic amine, dimethyldodecylamine, to the background electrolyte; the amine forms cationic micelles with a low critical micelle concentration (0.3 mM). The neutral micellar agent, Brij 35, competes with the amine for adsorption sites on the capillary surface decreasing the reversed electroosmosis. In such a system, mixed cationic micelles are formed to which the peptides were not distributed at low pH, but an improved resolution was obtained due to the effects on electroosmosis. In systems containing the less hydrophobic amine dimethyloctylamine, in which probably no mixed micelles are formed, an improved separation of protein kinase A peptide substrates was obtained due to distribution to Brij 35 micelles. In separations of enkephalins, a high pH gave very low efficiencies due to surface-analyte interactions, and the best CZE separations were obtained at low pH. Changes in migration order were observed in the pH range 2-3, possibly due to differences in peptide pKa values or conformation changes of the peptides. The enkephalins were only to a small extent distributed to the Brij 35 micelles, but this improved the separation at pH 2 compared to the CZE mode.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.1150160192
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  • 6
    Electronic Resource
    Electronic Resource
    Capillary zone electrophoresis and micellar electrokinetic chromatography, with taurodeoxycholate as micellar agent, of protein kinase A peptide substrates (1996)
    Weinheim : Wiley-Blackwell
    Electrophoresis 17 (1996), S. 161-167 
    Details
    ISSN: 0173-0835
    Keywords: Capillary zone electrophoresis ; Micellar electrokinetic chromatography ; Taurodeoxycholate ; Protein kinase A peptide substrates ; Structure - retention factor relationships ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: The separation of protein kinase A peptide substrates with the general formula -X-Arg-Arg-Ala-Ser-Y-, where X and Y may be the same or different amino aicds, was studied by capillary zone electrophoresis (CZE) and micellar electrokinetic chromatography (MEKC). Taurodeoxycholate (TDC) was used as the micellar agent. CZE was effective in separating a peptide series differing in the number of amino acids, but not for a series with a difference in the terminating amino acid. For the latter series, MEKC generally gave a higher selectivity, but some of the peptide pairs were more easily separated by CZE, demonstrating the complementary character of the two techniques. The efficiency of the MEKC system was typically 〈 50% of that of CZE, but its higher selectivity generally outbalanced the lower efficiency regarding resolution. The distribution of the peptides to the micelles was studied by determination of retention factors. Electrostatic and hydrophobic forces were found to be determining factors in the distribution; the most highly charged basic peptides were most heavily distributed, and for peptides with the same charge those containing more hydrophobic amino acids were more strongly distributed. The contribution of some structural features to the distribution degree was also determined.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.1150170126
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  • 7
    Electronic Resource
    Electronic Resource
    Indirect UV detection of carbohydrates in capillary zone electrophoresis by using tryptophan as a marker (1996)
    Weinheim : Wiley-Blackwell
    Electrophoresis 17 (1996), S. 325-332 
    Details
    ISSN: 0173-0835
    Keywords: Capillary zone electrophoresis ; Indirect UV detection ; Highly alkaline buffer ; Sugars ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: A rapid and sensitive method for the analysis of sugars was developed by capillary zone electrophoresis (CZE) with indirect UV detection. A mixture of nine mono- and oligosaccharides was separated in about 20 minutes on a fused silica capillary in a highly alkaline (pH 〉 12) background electrolyte (BGE). With tryptophan as the marker detected at 280 nm the femtomole level detection of sugars was possible. The system was optimized by studies on the buffer pH, the marker concentration, as well as the inner diameter of the capillary. The indirect detection of sugars was also performed with a cationic marker, N-benzylcinchonidium chloride (BCDC). However, the detection sensitivity was much lower in comparison to the tryptophan marker system.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.1150170207
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  • 8
    Electronic Resource
    Electronic Resource
    Enantioseparation of anaestethic drugs by capillary zone electrophoresis using cyclodextrin-containing background electrolytes (1998)
    Weinheim : Wiley-Blackwell
    Electrophoresis 19 (1998), S. 731-737 
    Details
    ISSN: 0173-0835
    Keywords: Enantioseparation ; Inclusion complexation ; Capillary zone electrophoresis ; Cyclodextrin ; Anaesthetic drugs ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: The enantiomers of five racemic anaestethic drugs were resolved with cyclodextrins using capillary zone electrophoresis. Parameters which affected the chiral resolution, such as type and concentration of cyclodextrin, temperature, and addition of organic modifier were investigated. The results show that the enantiomeric discrimination of the solutes is influenced by the structural shape of the solute molecules, separation temperature, and type of cyclodextrin. It was found that α-cyclodextrin was the best enantioselector for resolution of prilocaine and ketamine, while the enantiomers of mepivacaine, ropivacaine, and bupivacaine were resolved with β-cyclodextrin and/or modified β-cyclodextrins, i.e., methyl- and 2-hydroxypropyl-β-cyclodextrin, as chiral selectors. The length of the alkyl chain on the amino group of the drug molecule had a strong effect on the enantioresolution of mepivacaine, ropivacaine, and bupivacaine. Baseline separation of racemic ketamine was achieved with α-and methyl-β-cyclodextrin at 15°C. Addition of 5 M urea to the running buffer containing β-cyclodextrin at high concentrations resulted in the enantioseparation of prilocaine, mepivacaine, and ketamine. Enantioresolution was improved upon the addition of 10% methanol to the buffer containing urea and β-cyclodextrin. Generally, the complex formed between the S-enantiomers and modified β-cyclodextrins was stronger than the corresponding R-forms. An exception was prilocaine where the R-form gave a more stable complex both with α- and β-cyclodextrin.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.1150190522
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  • 9
    Electronic Resource
    Electronic Resource
    Performance of amino-silylated fused-silica capillaries for the separation of enkephalin-related peptides by capillary zone electrophoresis and micellar electrokinetic chromatography (1995)
    Weinheim : Wiley-Blackwell
    Electrophoresis 16 (1995), S. 557-563 
    Details
    ISSN: 0173-0835
    Keywords: Capillary zone electrophoresis ; Amino-coated capillaries ; Reversed electroosmosis ; Brij 35 ; Taurodeoxycholic acid micelles ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Enkephalin-related peptides were separated at low pH in a capillary with covalently bonded aminopropyl groups. The peptides are electrostatically repelled from the capillary surface and much higher efficiencies and faster separations were achieved compared to separations using uncoated capillaries. At low pH the amino groups are protonated, which results in reversed electroosmosis. The influence of voltage and ionic strength on the mobility and the separation efficiency was studied. The repeatability of migration times within one day was very good with relative standard deviations of 0.3-0.7%. Increasing the pH decreased the electroosmosis, eventually turning towards the cathode in the pH range 5-6; the separation performance, however, was lower at higher pH. Neutral and anionic micellar agents were added to the background electrolyte at different concentrations; the enkephalins had weak association with the neutral micellar agents but were distributed to the anionic taurodeoxycholic acid (TDC) micelles, giving rise to changes in separation selectivities. Very high efficiencies were obtained for peptides with a low distribution to the TDC micelles, while the efficiencies were impaired for those with a strong association with the micelles, which may indicate a slow mass transfer in the association process.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.1150160191
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  • 10
    Electronic Resource
    Electronic Resource
    Enantioresolution of disopyramide by capillary affinity electrokinetic chromatography with human α1-acid glycoprotein (AGP) as chiral selector applying a partial filling technique (1997)
    Weinheim : Wiley-Blackwell
    Electrophoresis 18 (1997), S. 950-957 
    Details
    ISSN: 0173-0835
    Keywords: Enantioseparation ; α1-Acid glycoprotein ; Capillary zone electrophoresis ; Disopyramide ; Partial filling technique ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: A method using α1-acid glycoprotein (AGP) as chiral selector for disopyramide by means of affinity electrokinetic chromatography has been developed. In order to avoid UV absorbance interferences, less than the effective length of the capillary was filled with the chiral selector. The electrophoretic conditions were chosen to give opposite migration directions for the chiral selector and the analyte; AGP migrated away from the detector. Enantiomers of disopyramide were separated on a methylcellulose-coated capillary with 20 cm length to the detector. The enantioresolution of the solute was affected by the concentration of the chiral selector, the plug length of the selector in the capillary, and the applied voltage. Resolution factors and migration times decreased with reduction of the plug length, while the efficiency of the separation system and peak performance were improved by decreasing the separation zone. A special feature of the technique is an enhanced selectivity due to increasing separation of the enantiomers when the fastest has migrated from the selector zone, while the second one still is retained. Equations relating selectivity and resolution with the difference in effective plug lengths between the two enantiomers are developed. Optimized conditions yielding complete resolution, requiring an 0.75 mM AGP plug of only 4.5 cm effective length, also gave high efficiencies (about 400 000 plates/m) for both enantiomer peaks.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.1150180616
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