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  • Biochemistry and Biotechnology  (7)
  • Capillary electrophoresis parameters  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Capillary electrophoresis analysis of isomeric truxillines and other high molecular weight impurities in illicit cocaine (1998)
    Weinheim : Wiley-Blackwell
    Electrophoresis 19 (1998), S. 51-56 
    Details
    ISSN: 0173-0835
    Keywords: Capillary electrophoresis ; Truxillines ; Cocaine ; Cyclodextrins ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: The analysis of by-products and impurities in illicit cocaine, including the isomeric truxillines, is important for derivation of both strategic and tactical intelligence. In the present study, various capillary electrophoresis techniques were investigated for this purpose. The use of the anionic β-cyclodextrin sulfobutyl ether IV as a run buffer additive at pH 8.6 gave a good separation of the truxillines and similar high molecular weight impurities in less than eight minutes. These impurities were first isolated from the bulk cocaine matrix using liquid-liquid extraction and size-exclusion high performance liquid chromatography. There was a red shift in the UV spectra obtained for the truxillines using photodiode array (PDA) UV detection during CE analysis. This anomalous behavior is attributed to photo-degradation of the truxillines during the PDA-UV irradiation process. Laser-induced fluorescence detection using a UV krypton/fluoride laser provided greater selectivity and sensitivity versus UV detection for certain uncharacterized high molecular weight impurities.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.1150190110
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  • 2
    Electronic Resource
    Electronic Resource
    Capillary electrophoresis of natural products (1997)
    Weinheim : Wiley-Blackwell
    Electrophoresis 18 (1997), S. 2438-2452 
    Details
    ISSN: 0173-0835
    Keywords: Natural products ; Capillary electrophoresis ; Micellar electrokinetic capillary chromatography ; Chinese herbal preparations ; Alkaloids ; Toxins ; Illicit drugs ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Capillary electrophoresis (CE) and micellar electrokinetic chromatography were used for the separation of widely different compounds from natural materials including antibiotics, humic substances, flavonoids, isoflavonoids, illicit drugs, coumarins, alkaloids, steroids, Chinese herbal preparations, nicotine, caffeine, amphetamines, toxins such as aflatoxins B1, B2, G1, G2, mycotoxins, heptapeptide aflatoxins and others, ephedrine compounds, mineral elements, and natural compounds in biological samples. A discussion of sample extraction and clean-up and the advantages of using CE is also presented.
    Additional Material: 25 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.1150181234
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  • 3
    Electronic Resource
    Electronic Resource
    Micellar electrokinetic chromatography of the anti-human immunodeficiency virus (HIV) agent michellamine B with absorption and laser-induced fluorescence detection (1994)
    Weinheim : Wiley-Blackwell
    Electrophoresis 15 (1994), S. 1310-1315 
    Details
    ISSN: 0173-0835
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Micellar electrokinetic chromatography (MEKC) was applied to the separation of the anti-HIV agents, michellamines A and B, and two other structurally related monomers found in the extract of the Ancistrocladus plants. Using buffers containing either 10 mM sodium phosphate (pH 7.0), 50 mM sodium de-oxycholate and 10-20% acetonitrile or 5 mM sodium phosphate (pH 7.0), 20 mM sodium dodecyl sulfate and 25% acetonitrile allowed baseline separations of the four components in the mixture in less than 10 min. The MEKC methods gave sharper peaks and better resolution compared to high-performance liquid chromatography. For MEKC separation of the plant extracts, UV absorption detection provided adequate sensitivity; however, higher sensitivity could be achieved with UV laser-induced fluorescence detection (LIF). Using the sodium dodecyl sulfate-containing buffer and LIF, the limit of detection for michellamine B was ∼ 2 ng/mL. The sensitivity was degraded ∼100-fold when using the deoxycholate buffer because of high background fluorescence. Preliminary results show that MEKC with LIF is feasible for the sensitive detection of michellamine B in serum.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.11501501199
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  • 4
    Electronic Resource
    Electronic Resource
    Separation and detection of amino acids and their enantiomers by capillary electrophoresis: A review (1995)
    Weinheim : Wiley-Blackwell
    Electrophoresis 16 (1995), S. 467-480 
    Details
    ISSN: 0173-0835
    Keywords: Capillary electrophoresis ; Amino acids ; Enantiomers ; Fluorogenic reagents ; Laser induced fluorescence detection ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Since its introduction as an analytical technique capillary electrophoresis has been used for the separation of amino acids and their enantiomers; over 150 studies have been published to date. This review deals with their separation and detection. Amino acids have been resolved using both capillary zone electrophoresis and micellar electrokinetic chromatography. Pre-column derivatization schemes which are employed for the sensitive detection of amino acids are discussed. Criteria for the selection of the pre- or post-column derivatizing agent, chromophore or fluorophore, are presented. Detection systems, direct and indirect, that have been used are given with emphasis on fluorogenic reagents and laser induced fluorescence detection. Also, procedures for the separation of amino acid enantiomers are discussed and illustrated.
    Additional Material: 21 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.1150160178
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  • 5
    Electronic Resource
    Electronic Resource
    Enantiomeric separation of amino acids using micellar electrokinetic chromatography after pre-column derivatization with the chiral reagent 1-(9-fluorenyl)-ethyl chloroformate (1995)
    Weinheim : Wiley-Blackwell
    Electrophoresis 16 (1995), S. 504-509 
    Details
    ISSN: 0173-0835
    Keywords: Micellar electrokinetic chromatography ; Enantiomers ; Cyclodextrin ; Amino acids ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Direct enantiomeric separations of some racemic amino acids derivatized with 9-fluorenylmethyl chloroformate were obtained using cyclodextrin-modified micellar electrokinetic chromatography (CD/MEKC) with a buffer made up of 5 mM sodium borate (pH 9.2), 150 mM sodium dodecyl sulfate (SDS) and 40 mM γ-CD. Alternatively, enantiomeric separations were also achieved indirectly using MEKC after pre-column derivatization with (+)-1-(9-fluorenyl) ethyl chloroformate (FLEC). Using either a 10 mM sodium phosphate (pH 6.8) or a 5 mM sodium borate buffer (pH 9.2), each of which contained 25 mM SDS and 10-15% of acetonitrile, FLEC-derivatized serine, alanine, valine, methionine, leucine, phenylalanine, tryptophan, and their diastereomeric pairs were all separated: the L-isomers migrated faster than the corresponding D-isomers. However, when (-)-FLEC was used for derivatization, the D-isomers migrated faster than the corresponding L-isomers. Also, the diastereomers of aspartic acid, glutamic acid, and proline were resolved using a 10 mM sodium citrate buffer (pH 4.4). Using KrF (248 nm) laser-induced fluorescence, the detection limit of (+)-FLEC derivatized DL-amino acids was obtained at the nM level, which was about 100 × more sensitive than UV absorption at 200 nm. Analyte concentrations as low as 3 × 10-8 M (DL-Val) could be derivatized with (+)-FLEC.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.1150160183
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  • 6
    Electronic Resource
    Electronic Resource
    Electrokinetic chromatography in suppressed electroosmotic flow environment: Use of a charged cyclodextrin for the separation of enantiomers and geometric isomers (1996)
    Weinheim : Wiley-Blackwell
    Electrophoresis 17 (1996), S. 1575-1583 
    Details
    ISSN: 0173-0835
    Keywords: Electrokinetic chromatography ; Charged cyclodextrins ; Geometric isomers ; Amino acids ; Dipeptides ; Chlorinated phenols ; Aflatoxins ; Polyacrylamide-coated columns ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Electrokinetic chromatography (EKC), with negatively-charged cyclodextrins (NCDs) added to the buffer, was conducted in polyacrylamide-coated columns under suppression of electroosmotic flow. The equations of migration and resolution for neutral solutes in this mode of chromatography, which for brevity we term NCD-EKC, are presented. The chiral sulfated cyclodextrin, β-CD-SBE (IV), used in this study is anionic over the entire pH range accessible to capillary electrophoresis, and the coated columns are stable and provide reproducible performance in the pH range 2.5-8.8. Optimum separation was obtained in the pH range where the solutes are neutral. The incorporation of an alkyl spacer between the sulfate ion and the rim of the cyclodextrin allows an unhindered approach and inclusion of neutral solutes in the cyclodextrin cavity. Solute migration time is inversely proportional to the concentration of the chiral selector. Separation (relative migration time difference) increases with decreasing chiral selector concentration and approaches a maximum, beyond which further decreases in chiral selector concentration result in broad peaks and loss of resolution. A chiral selector concentration of 1% in a 10 mM phosphate buffer produced excellent separation of amino acids and dipeptide enantiomers. In addition to being chiral selectors, cyclodextrins are also known as shape selectors. NCD-EKC is particularly suited for the separation of positional isomers of hydrophobic solutes. The separation of aflatoxin isomers and chlorophenol congeners is presented. In the separation of chlorophenols the more hydrophobic trichlorophenols eluted first and the least hydrophobic, phenol, eluted last.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.1150171014
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  • 7
    Electronic Resource
    Electronic Resource
    The effect of column length, applied voltage, gel type, and concentration on the capillary electrophoresis separation of DNA fragments and polymerase chain reaction products (1997)
    Weinheim : Wiley-Blackwell
    Electrophoresis 18 (1997), S. 1153-1158 
    Details
    ISSN: 0173-0835
    Keywords: DNA fragments ; Polymerase chain reaction products ; Short capillaries ; Capillary electrophoresis parameters ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: This work examines the effect of different parameters on migration time, resolution, and speed of analysis of DNA fragments and PCR products. These parameters include column length, applied voltage, gel type and concentration, and buffer ionic strength. Our results indicate that 1 cm capillary at an applied voltage of 185 V/cm, filled with commercial gel, was adequate for the separation of small DNA fragments in under 1 min. Resolution of large fragments is directly proportional to column length at the same field strength. Also, resolution of large fragments is higher (better) at lower field strength at constant column length. Analysis is fastest (high throughput) using a short capillary and moderate field strength (200 v/cm). CE using a single short capillary (2-7 cm) is comparable to slab gel in throughput, but more economical. The Sigma DNA buffer and hydroxyethyl cellulose liquid gel gave equivalent results in terms of resolution and reproducibility. The Sigma DNA replaceable gel gave reproducible results when used as received or diluted at 60%. In our hands hydroxyethyl cellulose gave more reproducible results than polyacrylamide gel.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.1150180722
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