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  • Articles  (77)
  • Capillary electrophoresis  (77)
  • Springer  (77)
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  • 1995-1999  (77)
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  • Chemistry and Pharmacology  (77)
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Monatshefte für Chemie 128 (1997), S. 795-804 
    ISSN: 1434-4475
    Keywords: Capillary electrophoresis ; Pyrimidines ; Micellar electrokinetic chromatography ; Organic solvents in capillary electrophoresis, Industrial product control
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Für die Bestimmung von Haupt- und Nebensubstanzen in technischen Proben von substituierten Pyrimidinen wurde ein kapillarelektrophoretisches Analysenverfahren entwickelt. Sowohl Zonenelektrophorese als auch mizellare elektrokinetische Chromatographie mit Trägerelektrolyten bestehend aus Boratpuffern (pH 9 bis 9.4) mit oder ohne Natriumdodecylsulfat wurden für die Trennung eingesetzt. Eine Optimierung der Trennselektivität war durch die Zugabe von bis zu 20% 2-Propanol oder Methanol zum Trägerelektrolyten möglich. Quantifizierung mittels interner Standards ergab relative Standardabweichungen zwischen 0.2 und 0.8%. Nebenprodukte konnten in technischen Proben bis zu Gehalten von 0.1% analysiert werden.
    Notes: Summary A capillary electrophoretic method has been developed for the determination of the main product as well as of by-products in technical samples of substituted pyrimidines. Both zone electrophoresis and micellar electrokinetic chromatography have been used for the separation employing electrolytes consisting of borate buffers (pH 9 to 9.4) with or without sodium dodecylsulfate. Optimization of separation selectivity could be achieved by addition of up to 20% 2-propanol or methanol to the carrier electrolyte. Quantification by internal standards resulted in relative standard deviations between 0.2 and 0.8%. By-products could be analyzed down to levels of 0.1% in technical samples.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Monatshefte für Chemie 128 (1997), S. 177-181 
    ISSN: 1434-4475
    Keywords: Amber ; Succinate ; GC-MS ; FTIR ; Capillary electrophoresis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Inklusionströpfchen des baltischen Bernsteins wurden mit Hilfe von GC-MS, FTIR Spektroskopie und Kapillarelektrophorese analysiert. Es stellte sich heraus, daß es sich dabei um Wasser handelt, in dem eine Reihe von anorganischen Kationen (Na+, K+, Ca2+, Mg2+) und Anionen (Cl−, Br−, NO 3 − , SO 4 2− ) gelöst sind. Darüber hinaus enthalten sie auch NH 4 + , Acetat- und Succinationen, wobei letztere in großem Überschuß vorhanden sind. Terpene waren jedoch nicht nachzuweisen. Aus diesen Ergebnissen wurde abgeleitet, daß die Inklusionströpfchen von salinem Spritzwasser stammen, in welches aus dem Bernstein stammende genuine Bernsteinsäure extrahiert worden war. Ammonium- und Acetationen könnten entweder aus den Inhaltsstoffen des Baumsaftes oder aus biogenen Materialien des Spritzwassers herrühren.
    Notes: Summary Baltic amber inclusion droplets were analyzed by means of gas chromatography, mass spectroscopy, FTIR spectroscopy, and capillary electrophoresis. It turned out that they were constituted of water in which a variety of inorganic cations (Na+, K+, Ca2+, Mg2+) and anions (Cl−, Br−, NO 3 − , SO 4 2− ) were dissolved. Moreover, NH 4 + , acetate, and succinate ions were detected with the latter strongly predominating. However, no terpenes could be traced. From these results it was concluded that the inclusion droplets stem from splash water of a saline environment into which amber genuine succinic acid was extracted. Ammonium and acetate ions could originate from either tree sap contents or biogenic contents of the splash water.
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  • 3
    ISSN: 1573-4943
    Keywords: Capillary electrophoresis ; peptides ; micropreparation ; matrix-assisted laser desorption/ionization mass spectrometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Signal suppression is a problem in matrix-assisted laser desorption/ionization mass spectrometry of peptides prepared by capillary electrophoresis. Many common electrolytes that are efficient for separation, such as sodium phosphate, also are strongly suppressive during laser desorption/ionization. We have tested individual electrolytes for highest performance in each step of separation and collection, respectively. Suppression is not observed if citrate, trifluoroacetic acid, or hydrochloric acid is used for collection, while phosphate still can be employed in the capillary providing excellent resolution. Low concentrations of hydrochloric acid added to the sample/matrix mixture generate mass spectra with better ion intensities than if trifluoroacetic acid or citrate is used.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 41 (1995), S. 631-637 
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Mycotoxins ; Selective analysis development ; Diode array detection ; Cyclodextrin-modified CE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The separation of the mycotoxins ochratoxin A, ochratoxin B, zearalenone and moniliformin by standard capillary zone electrophoresis (CZE) and cyclodextrins modified CE is described. In addition, reversed electroosmotic flow (EOF) conditions via quarternary ammonium running buffer additives have been briefly examined. Parameters influencing selectivity and mobility as well as spectroscopic properties of the analytes have also been investigated. Separations performed at pH values from 5 to 11 show a marked pH dependency of the mobilities accompanied by pronounced shifts of the UV/VIS and/or fluorescence spectra of the compounds. In general, the on-line recording of spectra by diodearray detection (DAD), proved to be highly versatile for peak tracking simultaneously with the structure elucidation and thus for the optimization of sample introduction, peak resolution and detection conditions.
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  • 5
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Quantitative determination ; Sodium ; Cephalothin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A capillary electrophoresis (CE) method for the quantitative determination of sodium levels in the sodium salt of an acidic drug has been transferred across 6 independent pharmaceutical companies. All companies were able to demonstrate similar selectivity and acceptable precision for migration times and relative migration times. Five companies obtained acceptable precision for the repeatability of response factors from repeated injections of calibration solutions. Highly variable results from the sixth company indicated problems arising from contamination from residual sodium, possibly from unclean glassware or autosampler vials. The quantitative assay results from all companies confirmed the correct drug: counter-ion ratio. The average % w/w sodium content was 5.45% which represents 99.0% of the theoretical sodium content of sodium cephalothin
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  • 6
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Surface modified capillaries ; Derivatized cyclodextrins ; Peak shape optimisation ; Enantiomer and rotamer resolution ; Remoxipride and local anaesthetic drugs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Dynamic coating of bonded C8 fused silica capillaries with cationic amphiphiles is shown to minimize adsorption of basic drug molecules but also to facilitate control/reversal of electroosmotic flow. Optimization of the peak shapes was achieved by addition of cationic amphiphiles with a suitable mobility and adsorption to the capillary surface. The surface modification described, combined with the addition of cyclodextrins as selectors into the background electrolyte, resulted in unique CE systems showing excellent resolution for structural analogues. The separation of rotamers and enantiomers is demonstrated. Applications to the antipsychotic compound remoxipride and its related substances and to the chiral separation of asthma- and local anaesthetic drug enantiomers are given.
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  • 7
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    Springer
    Chromatographia 40 (1995), S. 527-531 
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Trace analysis ; Dodecylbenzenesulphonate ; Detergent ; Validation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A capillary electrophoresis (CE) method is reported which allows both specific and sensitive detection of the surfactant sodium dodecylbenzenesulphonate (SDBS) at a trace level. The method employs a simple high pH electrolyte with detection at 200 nm. This method has been applied to the monitoring of detergent residues on pharmaceutical processing equipment left after cleaning. Successful validation of the method demonstrated acceptable levels of sensitivity, recovery, precision, repeatability, robustness, detector linearity and stability of standards, reagents and samples. The CE method for determination of detergent residue was demonstrated to be selective with no interference from dissolving water or from cotton wool extracts. The method is rapid and both simple and easy to perform, and is now routinely applied to monitor detergent residues following product manufacture.
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  • 8
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Laser induced fluorescence (LIF) detection ; Amino acid analysis ; FITC and DTAF derivatives
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Practical aspects related to the preparation of the fluorescein isothiocyanate (FITC) and dichlorotriazinylaminofluorescein (DTAF) derivatives of amino acids for purposes of quantitative analysis are examined and factors affecting quantification are discussed. It is shown that the labelling reaction for both reagents can be speeded up by operating at 40°C. The difficulties with derivatizing amino acids at detectable concentrations are highlighted. In spite of the high sensitivity of CE-LIF, detection sensitivity in real applications is limited by factors external to the analytical process, such as the label chemistry.
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  • 9
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Micellar electrokinetic chromatography ; Theoretical error prediction ; Optimization of experimental conditions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary This paper demonstrates that the relative standard deviation (RSD) of measurements in a capillary electrophoresis system can be predicted theoretically from the baseline and the signal shape at low sample concentration. The only requirements for prediction of the uncertainty are the Fourier transform of the baseline (here 2048 data points) and the observation of signal shape. The micellar electrokinetic chromatography (MEKC) of acetaminophen and caffeine is taken as an example. The optimum is defined here as the condition of the lowest RSD or highest precision. The optimum single wavelength is selected from between 220 and 350 nm for the MEKC system equipped with a photodiode array detector. The optimum time domain of signal integration is shown to be even narrower than the entire signal region, providing an RSD value about half that for integration of the entire region. The theory is in good agreement with observed RSD values.
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  • 10
    Electronic Resource
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    Springer
    Chromatographia 40 (1995), S. 163-169 
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; High speed separation ; Electrophoretic mobility ; Electroosmotic mobility ; N-Methylformamide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The organic solvent N-methylformamide (NMF) has been used as a separation medium in capillary electrophoresis. The advantageous properties of this compound are its high dielectric constant, high solubilizing power and low conductivity, as well as its amphiprotic character. It was shown that, unlike for most organic solvents, the electroosmotic flow is substantial. It was found to be possible to utilize NMF without added electrolyte. Field strengths exceeding 1000 volts/cm could be employed, while a low current was maintained and it was thus possible to obtain rapid analyses. Also, the properties of NMF allowed the analysis of substances with a low solubility in aqueous media. These features are exemplified by separation of carboxylic acids and pharmaceuticals. Excellent reproducibility of migration and no sign of electrical breakdown were observed, even under high field strength conditions.
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  • 11
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    Springer
    Chromatographia 40 (1995), S. 313-320 
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Repeatability ; Precision optimisation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A study has been performed to obtain insight into the relative importance of critical factors affecting the repeatability of hydrodynamic injections in CE. Precision was measured for repeated analysis of a test mixture containing two acidic compounds. The use of an internal standard was clearly shown to improve precision especially when peak area precision was poor. It is suggested that precision is maximised by employing a combination of a constant temperature, an appropriate electrolyte system, an internal standard, long injection times, and high sample concentrations. Other factors are discussed, but are classified as having only a minor impact.
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  • 12
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    Chromatographia 40 (1995), S. 375-378 
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Tobacco alkaloids ; Nicotine ; Aqueous tobacco extract ; Optimization of separation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Difficulties encountered in the gas or liquid chromatographic analysis of nicotine and other alkaloids in tobacco are largely due to the ionic character of these compounds. The potential of using capillary electrophoresis (CE) as an alternative analytical tool to eliminate these problems was evaluated. Parameters including electroosmotic flow, ionic forms of the analytes, buffer composition and applied voltage were studied using nicotine as a model compound. Ionic forms and electrophoretic mobility, as well as UV absorbance, of nicotine were controlled by varying the pH of an aqueous buffer solution. Thus the separation was optimized based on the characters of alkaloids and the nature of capillary electrophoresis. For tobacco samples in which nicotine accounts for more than 98% of the total alkaloid content, a quick method for the determination of nicotine in an aqueous tobacco extract within 100 seconds can be achieved.
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  • 13
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    Springer
    Chromatographia 41 (1995), S. 393-397 
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; High speed analysis ; Dissolution testing ; Pharmaceuticals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The quantitative use of high speed capillary electrophoresis (HSCE) is examined by applying high voltages across short capillaries. Acceptable performance in terms of injection precision and migration times were achieved within 1–2 minute analysis times. HSCE was used for the novel CE application of dissolution test sample solution analysis. The results generated by HSCE compared well with those generated using validated on-line UV absorbance measurements. It is concluded that HSCE is a viable alternative and supplement to standard analytical methods employed in dissolution test analysis.
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  • 14
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Enantiomer separation ; Cyclodextrins ; Pharmaceuticals ; Fenfluramine isomers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Capillary zone electrophoresis has been used for the enantiomeric separation of racemic ortho-fenfluramine and meta-fenfluramine employing a phosphate buffer at pH 2.5 added with cyclodextrins. The cyclodextrin type and concentration strongly influenced the chiral resolution. The uncharged β-cyclodextrin polymer gave enantiomeric resolution of both ortho and meta isomers, while γ-cyclodextrin was a good chiral selector for only ortho-fenfluramine; heptakis-2,3,6-tri-O-methyl-β-cyclodextrin permitted base line separation of meta-fenfluramine enantiomers but only partial resolution of racemic ortho-fenfluramine. The optimized electrophoretic method was applied to the quantitative analysis of 1-meta-fenfluramine (minor component in the mixture) and d-meta-fenfluramine in a commercial pharmaceutical formulation. Good reproducibility for migration time and corrected peak areas (R.S.D. 〈0.8% and 〈1.2%, respectively) was achieved and the presence of the minor component of the mixture was found to be in accord to previous determinations performed by other analytical methods.
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  • 15
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; 10-Hydroxy-2-decenoic acid ; Royal jelly
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The application of capillary electrophoresis (CE) to the separation and determination of the active ingredient, 10-hydroxy-2-decenoic acid, in royal jelly with direct on-column UV detection at 214 nm is described. Using a cathodic injection and anodic detection scheme, 10-hydroxy-2-decenoic acid (10-HDA) was separated and detected in less than 10 min in a fused silica capillary column with a phosphate buffer at pH 7.3 with an applied voltage of 20 KV followed by direct UV detection. The use of cetyltrimethylammonium bromide (CTAB) as electroosmotic flow modifier allows the rapid separation of 10-HDA from other constituents in royal jelly by reversing the direction of electroosmotic flow. The influence of organic solvents in the electrolyte on separation selectivity is also discussed.
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  • 16
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Diastereomeric isomers ; β-Cyclodextrin in the running buffer ; 1,3-Disubstituted tetrahydro-β-carboline
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Capillary zone electrophoresis with β-cyclodextrin as electrolyte additive has been investigated for the separation of the diastereomers of a 1,3-disubstituted tetrahydro-β-carboline. The effects of pH, buffer concentration, β-cyclodextrin concentration and applied voltage on resolution were investigated. This study shows that optimizing the assay conditions leads to maximum chiral separation or resolution. The method enables further research on the quantitative analysis of these compounds.
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  • 17
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Capillary electrophoresis ; Phenolic compounds ; Water samples
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A comparative study of high-performance liquid chromatography (HPLC) and capillary zone electrophoresis (CZE) for determination of eleven EPA priority phenols in water samples is discussed. The repeatability, linearity and detection limits of both methods are compared. A solid-phase extraction method using a highly cross-linked styrene-divinylbenzene copolymer sorbent is used for the off-line preconcentration process in order to determine these compounds in water at low levels. Both methods are used to determine phenolic compounds in Ebro river and industrial waste water. Identification was achieved by comparison of the UV spectra corresponding to the different peaks, acquired with a diode-array detector, with those in a spectral library.
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  • 18
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Adamantane derivatives ; 3-Cyclodextrin ; Indirect detection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Binding constants between adamantane carboxylic acids and β-cyclodextrin derivatives were determined by capillary electrophoresis (CE) using indirect detection. In this procedure, a mixture of adamantane derivative and non-interacting anionic standards, is injected and analysis of the electrophoretic mobility, relative to the noninteracting anionic standards, as a function of the concentration of cyclodextrin, yields values for their binding constants to the adamantane derivative. The usefulness of the method for quantification of binding constants is demonstrated.
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  • 19
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    Chromatographia 44 (1997), S. 367-371 
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Organic acids ; Pharmaceuticals ; Drug counter-ions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A capillary electrophoresis method is described for the novel application of quantifying levels of the simple organic acid counter-ions of a variety of basic drugs. These counter-ions are organic acids such as succinic and maleic. The method uses indirect UV detection and an electroosmotic flow modifier. Acceptable precision and detector linearity were obtained using internal standards. Method validation was completed and acceptable data was generated. The method is now in routine use for this type of testing.
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  • 20
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    Chromatographia 44 (1997), S. 514-520 
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Enzyme-catalyzed microreactions ; Nicotinamide adenine dinucleotide ; Quantitative analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary This work describes the quantitative analysis of incapillary enzyme-catalyzed microreactions using capillary electrophoresis. Migrating in a capillary under electrophoresis conditions, a plug of substrate and enzyme are injected separately, and allowed to react. Extent of reaction was subsequently determined by capillary electrophoresis. Two model systems were examined: the conversion of nicotinamide adenine dinucleotide (NAD) to nicotinamide adenine dinucleotide, reduced form (NADH) in the oxidation of glucose-6-phosphate (glc-6-p) to 6-phosphogluconate by glucose-6-phosphate dehydrogenase (G6PDH, EC 1.1.1.49), and the conversion of adenosine diphosphate (ADP) to adenosine monophosphate (AMP) by acid phosphatase (AP, EC 3.1.3.2.). These procedures illustrate the use of the capillary as a microreactor and the ease of quantitation of reaction products under conditions of electrophoresis. This technique offers a new and expeditious approach to analyzing enzymatic reactions on a microscale.
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  • 21
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    Chromatographia 44 (1997), S. 303-312 
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Indirect UV absorbance ; Alkaline metal and alkaline earths ; Lanthanides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The indirect UV detection of cations by capillary zone electrophoresis gives peaks of very different height or area between cations. We show that the height depends on the electrophoretic mobility of the cation compared with the electrophoretic mobility of the chromophore used. Moreover, the limit of detection can be easily improved by about 4-fold by adjusting the concentration of complexing agent or by using a chromophore with the same velocity as the studied cation. Using a new parameter termedsensitization power we can optimize the limit of detection and have determined the best chromophores for each family of cations.Sensitization power is a maximum for: alkali metals and alkali earths with imidazole and UV Cat 2®, for transition metal with pyridine, for light rare earth with ephedrine and UV Cat 1®, for heavy lanthanides with 1-naphthylamine and phenyl-trimethyl-ammonium bromide. Corrected areas of all cations studied have normal distributions directly proportional to their ionic charge. Certain behaviour can be predicted for elements such as actinides. Detection can also be enhanced because the relation of proportionality between ionic charge and corrected area allows comparison of the performance of all chromophores.
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  • 22
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Airborne particles ; Humic-like substances
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A considerable fraction of the refractory organic carbon in airborne particulate matter is to be attributed to humic-like substances (HULIS). Such atmospheric HULIS isolated from different air dust samples by a microscale extraction procedure were characterized by capillary electrophoresis (CE). For fractionation of HULIS the working conditions of the CE system were optimized using a borate buffer (pH 8.2), polyacrylamide (PAA) coated, fused-silica capillary and polyethylene glycol as sieving modifier. Using CE under optimized conditions, HULIS produced electropherograms showing well resolved and reproducible signals.
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  • 23
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    Chromatographia 47 (1998), S. 249-256 
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Cyclodextrin mobile phase additives ; Synthetic food colorants ; Selectivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A high-performance capillary electrophoresis method with diode-array detection has been developed for analysis of synthetic food colorants. The influence of buffer composition on the separation of the food colorants was examined, as were the effects of α-, β- and γ-c-yclodextrins on analyte migration behavior. Eight food colorants were completely separated within 10 min using pH 9.5 borax—NaOH buffer containing 5 mM β-cyclodextrin. Experimental results indicate that the relative standard deviations of analyte migration times were〈0.88% under the optimized separation condition. Correlation coefficients of the linear calibration plots of the analytes exceeded 0.998. The method was suitable for determination of the quantities of synthetic food colorantsi in ice cream bars and fruit soda drinks.
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  • 24
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    Chromatographia 48 (1998), S. 355-359 
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Cathodic flow electrode ; Electrolyte buffer depletion ; Reproductibility and precision
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The effects of electrolyte buffer depletion is well recognised and regular replacement of the electrolyte can prevent poor reproducibility. We have further investigated the effect of electrolyte depletion and produced a modified cathodic flow electrode to improve reproducibility using minimal volumes of electrolytes.
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  • 25
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Enantiomers ; Epinephrine ; Experimental designs ; Optimization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A capillary electrophoretic method using a chiral selector was optimized by experimental design for the enantioresolution of epinephrine enantiomers. Two β-cyclodextrins derivatives, namely heptakis-2,6-di-O-methyl-β-cyclodextrin and carboxy-methyl-β-cyclodextrin, respectively neutral and charged, were used as chiral selectors employing an uncoated capillary. By using a statistical experimental design in which all factors are varied at the same time, it was possible to optimize the method with regard to the resolution between peaks and the two migration times. A fractional factorial design and a central composite design were used. A compromise between conflicting goals, such as maximization of resolution and minimization of analysis time, was found by means of a desirability function D. Balancing these goals against each other, the most acceptable solution to the problem was found and the optimized method gave a fast separation with complete resolution between the adrenaline enantiomers. The response surfaces obtained confirmed the robustness of the method.
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  • 26
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; pK A determination ; Indirect UV detection ; Alkyl-alkyl phosphonic acids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Capillary electrophoresis (CE) has proved to be a fast and convenient method for the determination of the dissociation constants of non-UV absorbing solutes in the acidic pK A range (2.0–2.5). The electroosmotic flow was reversed by washing the capillary with 0.2% polybren aqueous solution. A series of background electrolytes was prepared with phenylphosphonic acid (pK A=1.29) and β-alanine (pK A=3.55) with the same ionic strength and a high buffer capacity in order to improve the repeatability (0.1–0.2 %) of the electrophoretic mobility and to determine the values of pK A accurately. This procedure was applied to the determination of the dissociation constants of several alkyl-alkylphosphonic acids whose pK A values have not yet been published in the literature. In this work, their dissociation constants have been found to vary between 1.91 and 2.34 for alkyl-methylphosphonic acids and between 2.10 and 2.38 for alkyl-ethylphosphonic acids.
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  • 27
    ISSN: 1612-1112
    Keywords: Review ; Capillary electrophoresis ; DNA ; Oligonucleotides ; Pluronic polymers ; Liquid crystals ; Micelles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The liquid crystalline gel phases of solutions of Pluronic F127, a triblock copolymer, were recently introduced as an alternative to disordered solutions of random coil polymers as replaceable media for capillary gel electrophoresis (CGE). Pluronic F127, from BASF, is a copolymer of poly(ethylene oxide) and poly(propylene oxide) with the approximate formula (EO)106 (PO)70 (EO)106. Polymer chains aggregate into spherical micelles in aqueous solutions, with poly(propylene oxide) chains creating a hydrophobic core surrounded by brushes of hydrated poly(ethylene oxide) tails. Crowding at high concentrations promotes ordering of micelles. Solutions in the range of about 14–24 % polymer are self-supporting, gel-like cubic liquid crystals at 25–30°C, but when cooled they become low viscosity liquids that are easily loaded into capillaries. This article reviews applications of Pluronic F127 media for capillary gel electrophoresis separations of nucleic acids of several types including oligonucleotides, double stranded DNA fragments, and supercoiled plasmid DNAs.
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  • 28
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    Chromatographia 49 (1999), S. S79 
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Diagnosis of myelomatosis ; Metabolic disorders ; Serum proteins ; CE-MS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary CE is used both for routine clinical analysis and for specialized clinical investigations. CE analysis of serum proteins is fast and reliable, with immunosubtraction for identification of immunoglobulins. This method was used to show the appearance of a pathological protein many years prior to the diagnosis of myelomatosis. CE with diode array detector and CE-MS were suitable for the diagnosis of a number of metabolic disorders. Online analyte concentrators are sometimes required to enhance the concentration sensitivity of CE.
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  • 29
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    Chromatographia 49 (1999), S. S87 
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Electrospray-ionization ; Ion trap mass spectrometry ; Separation of compounds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Capillary electrophoresis (CE) coupled with mass spectrometry (MS) has proven a powerful alternative to conventional chromatographic separation techiques. Here the analysis of various compounds with a novel CE ESI sprayer and an ion trap mass analyzer is described.
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  • 30
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Cleaning qualification ; Trace level analysis ; Pharmaceuticals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The novel use of capillary electrophoresis to the important and developing area of monitoring possible drug residues on pharmaceutical manufacturing equipment is reported. The CE method is applicable to a wide range of basic drugs with sensitivity as low as 25ng/ml (equivalent to 8×10−8 M). This sensitivity is equivalent to that obtainable for HPLC for the drugs tested and is obtained by employing a combination of a wider bore capillary with low wavelength UV detection. Preliminary evaluation of the method performance shows acceptable precision, linearity, sensitivity and accuracy. Features of the method compared to HPLC include simplicity, ease of method transfer, reductions in analysis set-up time, and reduced costs of solvents and columns.
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  • 31
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Capillary electrophoresis ; Enantiomer separation ; Trimetoquinol ; Denopamine ; Timepidium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Two methods for the direct separation of the enantiomers of trimetoquinol hydrochloride, denopamine and timepidium bromide were investigated, namely capillary zone electrophoresis (CZE) using cyclodextrins (CDs) (CD-CZE) and high-performance liquid chromatography (HPLC) using chiral stationary phases (CSPs). By CZE, separation of the enantiomers of trimetoquinol was successfully achieved when using β-cyclodextrin (β-CD), heptakis(2,6-di-0-methyl)-β-cyclodextrin (DM-β-CD) and β-CD polymer, but direct HPLC separation of the enantiomers was not successful. The enantiomers of denopamine were successfully separated by both CZE, employing DM-β-CD under acidic conditions, and HPLC, with cyclodextrin immobilized CSPs (CD-CSPs). Timepidium bromide, which is a racemic drug, was successfully enantioseparated by both CD-CZE and HPLC with CD-CSPs. The CD-CZE mode was selected as the optical purity testing method for trimetoquinol and denopamine because of the superiority of capillary electrophoretic (CE) techniques. Method validation results obtained clearly show that the CE method would be useful as an quality control method for assessing the optical purity of the drugs.
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  • 32
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Micellar electrokinetic capillary chromatography ; Sensitized lanthanide ion luminescence ; Orotic acid
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    Topics: Chemistry and Pharmacology
    Notes: Summary A sensitive and selective laser-induced luminescence detection scheme for orotic acid in urine, separated by micellar electrokinetic capillary chromatography (MEKC) has been developed. The 325 nm line from a helium cadmium laser is used to excite orotic acid, which transfers its energy to terbium. Resultant luminescence of terbium is linear with orotic acid concentration over more than 2.5 orders of magnitude. This novel and practical system enables the detection of 50 nm orotic acid in urine in less than 1.5 minutes while using only nanoliters of sample. The significant decrease in analysis time over traditional methods (spectrophotometric and chromatographic) comes from the high efficiency of MEKC. A dramatic improvement in sensitivity and selectivity over UV detection in capillary electrophoresis is achieved through the use of laser-induced lanthanide ion energy transfer luminescence detection. Finally, no sample pretreatment is needed and the method is free from any known interferences in urine.
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  • 33
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    Chromatographia 42 (1996), S. 323-328 
    ISSN: 1612-1112
    Keywords: Supercritical fluid extraction ; Capillary electrophoresis ; Carbamates residues ; Tobacco samples
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    Topics: Chemistry and Pharmacology
    Notes: Summary Determination of carbamate residues in tobacco samples was carried out by solid-liquid extraction (SLE) and supercritical-fluid extraction (SFE) methods, both developed for this purpose. The clean-up step was carried out on SPE-Florisil cartridges and the extracts analysed by capillary zone electrophoresis (CZE) with UV detection. The results were compared and SFE using CO2-acetone showed the best results in terms of recovery and generally higher extraction power. SFE in conjunction with CZE proved suitable for carbamate residue analysis in real tobacco samples.
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  • 34
    ISSN: 1612-1112
    Keywords: Review ; Capillary electrophoresis ; Pharmaceutical raw materials ; Excipients
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The use of capillary electrophoresis for the separation and quantitation of a range of pharmaceutical raw materials and excipients is reviewed. Capillary electrophoresis is shown to be a useful and versatile technique for a large number of applications. Features of the various methods include simplicity, detection of poor chromatophore species by extensive use of indirect UV detection or direct absorbance at low wavelengths, minimal operating costs and generation of high quality retrievable raw data. Specific novel examples described include separations of lactose, flavouring agents, inorganic salts, lecithin constituents, a range of organic acids, benzylalkonium chloride components, sodium lauryl sulphate, and the quality of input water. It is concluded that the versatility of CE will ensure that it is increasingly used in the analysis of pharmaceutical raw materials and excipients.
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  • 35
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    Chromatographia 43 (1996), S. 200-204 
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Capillary joining
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    Topics: Chemistry and Pharmacology
    Notes: Summary Aspects of cracking and joining capillaries have been investigated. Capillary coupling was achieved using various methods. The most successful used hydrofluoric acid-etched capillaries to form male and female ends which were then joined together. This type of joint was used to connect sections of capillary of similar and different internal diameters with minimal loss in resolution, peak width and number of theoretical plates. (Uridine and hypoxanthine was used as a test mixture). For hypoxanthine on a 50 μm/50 μm etched joined capillary 10 cm from the detector window the number of theoretical plates was 96.6% of that for hypoxanthine on an unbroken capillary. Following the relative success of capillary joining, a coupled capillary flowcell (50 μm/200 μm) was produced and evaluated.
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  • 36
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Non-aqueous electrolytes ; Chiral separation of dansyl amino acids ; N-methylformamide ; Formamide
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    Topics: Chemistry and Pharmacology
    Notes: Summary Chiral separation of 12 dansyl amino acids has been achieved by capillary electrophoresis using β-cyclodextrin dissolved inN-methylformamide or formamide. The viscosity and the dielectric constants of these two solvents are very different, giving them disimilar electrophoretic properties. Intense electroosmotic flow, high electrophoretic mobilities and high efficiency were achieved inN-methylformamide, but high chiral selector concentration was needed for sufficient resolution. In contrast, the separation of dansyl amino acids in formamide was characterized by longer analysis time and lower efficiency, but the resolution and selectivity of the separation were better and baseline separation could be achieved at lower β-cyclodextrin concentrations.
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  • 37
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    Chromatographia 43 (1996), S. 247-253 
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Enantiomers ; Chiral resolution ; Cyclodextrin derivatives ; Drugs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary β-cyclodextrin derivatives, namely 6A methylamino-β-CD and hepta-methylamino-β-CD have been used as chiral selectors for the enantiomeric separation of a number of acidic and basic compounds by capillary electrophoresis employing either coated or uncoated capillaries. The effects of the CD type and concentration and the pH of the background electrolyte on the mobility and chiral resolution of the analytes have been studied. The use of monomethylamino-β-CD in a coated capillary allowed the enantiomeric resolution of phenyl lactic acid, warfarin and acenocoumarol but was not successful for tiaprofen and its 3-isomer. The heptamethylamino derivative, under the same experimental conditions, was a better chiral selector than the monosubstuted CD toward the arylpropionic acids and phenyl lactic acid while the anticoagulant drugs showed poor or no chiral resolution. Inversion of migration order was obtained for phenyl lactic acid, warfarin and acenocoumarol enantiomers. The enantiomers of basic compounds of pharmaceutical interest, namely propranolol, terbutaline, ketamine, chlorpheriramine and isoproterenol were only resolved using monomethylamino-β-CD dissolved in a phosphate buffer containing tetramethylammonium ions.
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  • 38
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Short-end injections
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Minimum capillary lengths on commercial instruments are fixed and cannot be decreased further. To effectively reduce the capillary length used for separation the sample can be injected from the end of the capillary nearest the detector. This procedure is known as a ‘short-end’ injection and can reduces analysis times by at least two-thirds compared to conventional injections. The time reduction benefits are shown in rapid separations of basic drugs, drug-related impurities and chiral compounds. Short-end injections, in combination with both increased electrolyte strength and reduced voltage are an effective approach to reducing the detrimental impact of high sample solution ionic strength. They can also lead to improved resolution by increasing stacking effects and reducing peak tailing. Peak area and migration time precision obtained are shown to be equivalent to those obtained for conventional injection procedures. It is concluded that short-end injections should be considered for routine operation as they are a useful means of reducing analysis time, increasing sensitivity, decreasing buffer depletion effects. They also allow use of higher electrolyte strengths which can improve resolution and reduce peak tailing, and can overcome significant problems which occur when analysing samples containing high salt contents.
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  • 39
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Micellar electrokinetic chromatography ; Retention factors ; Band broadening ; Stepwise modifier gradient
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    Topics: Chemistry and Pharmacology
    Notes: Summary Gradient elution in micellar electrokinetic chromatography has been proposed as a technique for extending the elution range and adjusting retention factors for optimum values. It is shown that this approach in practice has not only to be evaluated for adjustment of retention factors but also for the reduced efficiency of the chromatographic system arising from alterations in the separation buffer during the run. Stepwise gradient elution, feasible with commercial instrumentation, results in marked peak broadening attributable to effects of the border zone passing the solute zone.
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  • 40
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Chiral separtions ; Chromane ; Cyclodextrin ; Screening design
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    Topics: Chemistry and Pharmacology
    Notes: Summary Six different cyclodextrins with varying cavity size and rim substitution were used as chiral agents for the enantiomeric separation of eight chromane compounds or analogues using capillary electrophoresis. It is shown that the cyclodextrin type and concentration have a large influence on the enantiomeric separation obtained for these compounds. A chiral resolution of 1.4 or better could be obtained for all the substances with either substituted heptakis(2,3,6-tri-O-methyl)-β-cyclodextrin or unsubstituted γ-cyclodextrin as the chiral selector. The influence of the γ-cyclodextrin concentration, ionic strength and pH on the chiral separations was also investigated with a multivariate screening design. The detection limit and resolution of the present method allow determinations of the investigated compounds down to a chiral impurity of less than 0.1 % (area/area).
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  • 41
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    Chromatographia 44 (1997), S. 129-134 
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Temperature control ; Thermostating
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The use of high voltages across a electrophoresis capillary will increase the temperature of the buffer due to Joule heating. As a result temperature control in CE is rather important since variations in the buffer temperature will result in changes in the pH of the buffer, peak shape, migration time, reproducibility, efficiency, 3-D structure of macromolecular analytes, etc. Six different thermostating systems have been evaluated: (i) natural convection, (ii) fan, (iii) home-made and (iv and v) two commercially available high-speed air and a (vi) liquid thermostated device. In all cases the temperature of the buffer in the capillary is calculated according to the temperature-conductivity relationship. For this purpose two parameters are introduced describing temperature control: the temperature onset (δT) and the temperature rise factor (α). From these results, it can be concluded that high speed air thermostating can be as efficient as liquid thermostating.
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  • 42
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Aldehydes ; Hydrazino benzene sulfonic acid ; Water analysis
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    Topics: Chemistry and Pharmacology
    Notes: Summary A method has been developed for the analysis of environmentally important aldehydes in rain water. The method is based on the derivatization of the aldehydes with hydrazino benzene sulfonic acid, separation of the hydrazones formed by capillary electrophoresis and UV detection at 280 nm. Derivatization was shown to be complete in 15 min at 50°C. The aldehyde derivatives could be separated from each other and from the excess of reagent using a pH 9 borate buffer as background electrolyte, with an analysis time of less than 6 min. The repeatability was better than 0.5% for the peak mobilities and in the order of 2–5% for the peak areas. Detection limits of 0.8–3 μmol L−1 (0.02–0.2 ppm) were obtained. The method was applied for the determination of formaldehyde and acetaldehyde in rain water samples.
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  • 43
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    Chromatographia 48 (1998), S. 569-575 
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Oligonucleotides ; Dextran ; Polymer solution ; Purity testing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Capillary gel electrophoresis (CGE) has been recognized as an effective method for the analysis of oligonucleotides. CGE using polymer solutions is especially useful and effective compared with that using crosslinked gels, because of easy change of media. Replacement of media leads to the reproducible separation of analytes. We have investigated CGE analysis of oligonucleotides of less than 20 bases employing various kinds of polymers. Polyacrylamide, dextrin, dextran, pullakin, and poly(ethylene glycol) were used as sieving matrixes at concentrations of 0–30 %. Polydeoxythymidylic acids [p(dT)11–20] were used as a test sample. These small oligonucleotides were successfully resolved on the basis of their base number by CGE using some of these polymer solutions. In particular, dextran was found to be effective and baseline separation was observed when a 30 % dextran solution was employed. Some validations such as linearity and reproducibility were also established and this method was found to be an adequate quality control method for small oligonucleotides. Finally, CGE using a 30 % dextran solution was successfully applied to impurity profiling of some synthetic oligonucleotides.
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  • 44
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    Chromatographia 48 (1998), S. 739-744 
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Nucleotides ; Inorganic cations ; Complexation with Mg and Ca
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The complexation equilibrium between nucleotides (ATP, ADP) and inorganic cations (Mg2+, Ca2+) has been studied by capillary electrophoresis. The equilibrium constant and the stoichiometry of nucleotide-inorganic cation complexes can be deduced from the dependence of the electrophoretic mobility of each nucleotide on the negative logarithm of the inorganic cation concentration. The experimental values of complexation constants determined by CE compare favorably with those in the literature. As expected, Mg2+ forms more stable complexes with ATP (logK=2.30 and 4.10 at pH 5 and 8, respectively) than with ADP (logK=1.92 and 3.15 at pH 5 and 8, respectively). In the pH range 4–8, the stoichiometry of ADP-Mg2+ and ADP-Ca2+ complexes is always 1∶1 whereas that of the complexes between these cations and ATP depends on pH-hence ATP-Mg2+ and ATP-Ca2+ complexes have 1∶1 stoichiometry at pH 5 and 1∶2 at pH 8.
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  • 45
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Conductivity tuning ; Chiral separation ; Peak symmetry ; Resolution expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Different approaches how to handle the electromigration dispersion process that occurs in separation and determination of enantiomers are presented. The use of cyclodextrins as chiral selectors in resolution enantiomers involves the possibility to tune the conductivity of the sample band in order to obtain symmetrical and efficient peaks. Determination of impurities that migrate in the rear part of an overloaded main peak can be accomplished if the conductivity of the background electrolyte (BGE) is adapted to the conductivity of the sample band. This strategy was shown in determination of the content of D-sotalol in a mixture of L and D-sotalol. The efficiency and the symmetry of the overloaded L-sotalol peak was substantially improved by substitution of tetrabutylammonium ions for tetrapentylammonium ions as co-ions in the BGE. In this system it was possible to determine 0.2% w/w of the chiral impurity D-sotalol. A resolution model is presented and used qualitatively in the study where the complexation between the tetraalkyllammonium ions and the cyclodextrins is taken into account.
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  • 46
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Anions ; System peaks
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary This study deals with the simultaneous analysis of UV-transparent anions by capillary electrophoresis with indirect UV-detection. With a background electrolyte (BGE) based on UV-absorbing chromate and UV-transparent borate, the interference of system peaks with those of sample anions (chloride, sulfate, citrate, phosphate) is shown. The existence of such system peaks, and their position in relation to the peaks of the sample anions, are explained on the basis of the eigenpeak theory proposed by Poppe [1]. With this BGE the system peaks were manifested as a negative peak followed by a positive peak. Their shapes depended on the relative mobilities of the analyte and BGE anions and their areas depended on the amount of sample. The mobility of the system peak depends on the borate/boric acid mobility, which was adjusted by slight variation of the pH close to its pK a-pH is the key factor governing system-peak mobility. When the locations of the system peaks are optimized, the quantification of citrate can be achieved; this was successfully used for determination of anions in milk.
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  • 47
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    Chromatographia 49 (1999), S. 343-346 
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Frontal analysis ; Binding constants ; Basic drugs ; Human serum albumin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The applicability of capillary electrophoresis/frontal analysis (CE/FA) for determining the binding constants of the drugs propranolol (PRO) and verapamil (VER) to human serum albumin (HSA) was investigated. After direct hydrodynamic injection of a drug-HAS mixture solution into a coated capillary (32 cm × 50 μm i.d.), the basic drug was eluted as a zonal peak with a plateau region under condition of phosphate buffer (pH 7.4; ionic strength 0.17) at 12 kV positive running voltage. The unbound drug concentrations measured from the plateau peak heights had good correlation coefficients,r〉0.999. Employing the Scatchard plot, the Klotz plot and nonlinear regression, the drug protein binding parameters, the binding constant and the number of binding sites on one protein molecule, were obtained. The binding constant obtained was compared to a reported equilibrium dialysis result and they are basically in good agreement.
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  • 48
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    Chromatographia 49 (1999), S. 379-384 
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Nucleotides ; Cadmium complexation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The CE separation of twelve nucleotides (5′-mono-, di-, triphosphates of adenosine, guanosine, cytidine and uridine) was improved by adding cadmium ion to the ammonium citrate/citric acid buffer (pH 5, ionic strength 100 mM). Cadmium ion acts as a complexing agent for some nucleotides (ATP, CTP, GTP, UTP, GDP). In order to accelerate the separation, the electroosmotic flow was reversed by flushing the fused-silica capillary with 0.2 % aqueous solution of the polycationic surfactant hexadimethrine bromide. A good separation of the twelve nucleotides studied was then achieved on a dynamically coated capillary in less than 5 min by using an ammonium citrate/citric acid buffer (pH 5, ionic strength 100 mM) to which 2 mM cadmium ion has been added. High peak efficiencies were obtained (210 000 theoretical plates) and the resolution between two adjacent peaks was always greater than 1.5.
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  • 49
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    Chromatographia 49 (1999), S. 406-410 
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Pharmaceutical Analysis ; Lactose
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A CE method has been validated for the analysis of batches of lactose used as a pharmaceutical raw material. This method was shown to be selective for lactose and was found to be quantitative. The separation was achieved due to on-capillary chelation of the lactose with borate ion. The resulting complex was detected at 195nm. An internal standard is employed to improve injection precision and detector linearity. A system peak occurred in the separation and was systematically investigated to show that it was not sample related. The method was validated and successfully submitted to regulatory authorities and is now in routine use in a number of our quality control laboratories.
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  • 50
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Membrane proteins ; Serine receptor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Capillary zone electrophoresis (CZE) was applied to the characterization of the transmembrane serine receptor in biosynthetic samples. The serine receptor, otherwise known as Tsr (taxis to serine and repellents), is a ∼ 60,000 Dalton intrinsic membrane protein whose periplasmic domain (ligand binding domain) reversibly binds the amino acid serine. In general, the electrophoresis of intrinsic membrane proteins is difficult due to severe solubility problems and adsorption which occurs during the electrophoretic run. This is due to the tendency of these types of proteins to undergo aggregation, self-aggregation and precipitation in aqueous environments. The addition of percentage levels of the surfactant, sodium dodecyl sulfate (SDS), to a tetraborate run buffer was shown to be effective both in enhancing the solubility of intact Tsr and in preventing the adsorption of intact Tsr to the fused-silica capillary wall during electrophoretic analysis. Critical separation parameters such as run buffer concentration, surfactant concentration and surfactant type were optimized to give the best separation profiles.
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  • 51
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Micellar electrokinetic capillary chromatography ; Nonaqueous media ; Tropane alkaloids ; Hyoscyamine and scopolamine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The potential of nonaqueous capillary electrophoresis has been investigated for the separation of structurally similar tropane alkaloids. The effects of the organic solvent and of electrolyte composition on separation selectivity, migration times, and efficiency are described. The addition of trifluoroacetic acid to the separation buffer was found beneficial for manipulation of the order of migration of the two positional isomers littorine and hyoscyamine. Replicate injections under nonaqueous conditions gave migration time and peak area data of excellent precision. The application of the optimized conditions to the analysis of hyoscyamine and scopolamine in genetically transformed root cultures ofDatura candida x D. aurea is presented.
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  • 52
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    Chromatographia 49 (1999), S. 71-74 
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Serum analysis ; Total iron binding capacity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A capillary electrophoresis (CE) technique for determining total iron binding capacity (TIBC) of serum has been developed. The optimum serum pretreatment involves the following major steps: at first, saturate serum transferrin with Fe+3; then, dissociate them completely after removing excess unbound Fe. Finally, complex the released iron with phenanthroline, a chromophore, to make suitable for the CE analysis. Ammonium acetate (pH=5.0) was used as CE background electrolyte solution. In this system, a good linear correlation coefficient was maintained over the range 0.5≈10 μM (r=0.9979,n=12). Seven adult serum samples were studied and the TIBC parameters measured. In the present system, 10≈30 μL serum is sufficient for determination. The study shows that the CE technique described is a powerful method for rapid, efficient, sensitive and reliable analysis and hence particularly suitable for clinical application.
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  • 53
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Field-amplified sample stacking ; Water plug ; Drugs in biological fluids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Strategies to improve the sensitivity of drug monitoring in microliter amounts of biological fluids by capillary electrokinetic methods are currently being explored in our laboratory. Head-column field-amplified sample stacking is the most effective method of sensitivity enhancement—this approach is robust and highly reproducible when applied correctly. For analysis of opioids as standards or in plasma extracts by binary capillary electrophoresis with ethylene glycol, the data presented in this work unambiguously demonstrate that the water plug initially inserted at the column inlet is essential for establishing a steady current during separation, and thus the highest reproducibility. Internal calibration shows thatRSD imprecision values otherwise up to approximately 30% are reduced to values significantly below 10%. The water plug also results in higher detector responses at elevated solute levels (≥100 ng mL−1) and leads to increased sensitivity when the sample (standards and extracts of body fluids) is dissolved in water. The water plug does not, however, furnish higher sensitivity in the analysis of opioids as standards or in plasma extracts that are prepared in the optimized sample solvent or buffer. The optimum length of the water plug cannot, furthermore, be obtained merely by dipping the capillary inlet into water (insertion of water by capillary action). The water zone obtained in this way must be elongated by approximately 0.6 mm by deliberate hydrodynamic introduction of additional water from a different vial. These head-column field-amplified sample-stacking conditions are shown in operation on two different commercial instruments. As an illustration, data are presented depicting the analysis of dihydrocodeine and nordihydrocodeine in plasma and urine specimens of individuals to which dihydrocodeine was administered.
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  • 54
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Anion exchange chromatography ; Carbohydrate ; Derivatization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The derivatization process of malto-oligosaccharides by means of reductive amination for the subsequent separation by capillary electrophoresis (CE) is investigated. Aminonaphthalene-disulfonic acid was used as derivatization agent for this purpose. The molecular weight distribution found by CE differed significantly from that measured by anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD). While the proportion of maltodextrins with lower molecular weight was higher in CE than in HPAEC-PAD, the opposite hold for oligomers with higher molecular weights. An investigation of the derivatization process provided strong indications that degradation of higher molecular weight oligomers could be the reason for these differences. The derivatization process was optimized with respect to minimal degradation expressed as the peak area ratio of maltose to maltoheptaose at simultaneously maximal reaction rate expressed as the peak area of maltoheptaose by using a Box-Behnken design. It was found that only a compromise allowed both sufficient reaction turnover and low degradation of the oligomers. This technique could be employed successfully to analyze maltodextrins and oligomannans in coffee.
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  • 55
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Coelectroosmotic flow ; Osmotic modifiers ; Aromatic sulphonate compounds ; Organic solvents
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Coelectroosmotic capillary zone electrophoresis (CZE) has been investigated as a means of rapid analysis of twelve aromatic sulphonate compounds. The main factors affecting reversal of electroosmotic flow (EOF)—type of osmotic modifier and concentration-were studied. Two types of osmotic modifier, an alkylammonium salt (cetyltrimethylammonium bromide, CTAB) and a cationic polyelectrolyte (hexadimentrine bromide, HDB) were investigated. The composition of the running buffers was optimized according to the characteristics of each osmotic modifier. A concentration of HDB as low as 0.0001% (w/v) was used successfully to provide a stable and reversed EOF.
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  • 56
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Column technology ; Deactivation ; Polyethyleneoxides ; Ribonucleotides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary In this study, a variety of fused silica capillaries with different combinations and sequences of treatments with HMDS and polyethylene oxide were prepared in order to develop an optimized column modification method for analysis of ribonucleotides. The 12 most common ribonucleotides (UTP, CTP, ATP, GTP, UDP, CDP, ADP, GDP, UMP, CMP, AMP, and GMP) in human cells were used as test solutes. Column performance measurements, including electroosmotic flow (EOF), solute migration speed and retention, column efficiency, peak shape, and resolution were investigated. By analyzing solute migration speed and retention of various hydrophilic/hydrophobic solutes, the column wall effects (EOF and adsorption) can be distinguished. This analysis method can give guidance in optimizing polymer coating properties (hydrophilicity/hydrophobicity) for CE columns. By studying the performance of these columns after various surface treatments, we were able to improve the separation of ribonucleotides from real samples to within 16 minutes with high efficiency and stability (over 300 analyses) using columns first deactivated with hexamethyldisilazane, and then coated with polyethylene oxide.
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  • 57
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    Chromatographia 40 (1995), S. 175-184 
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Critical micelle concentration ; Retention factors ; Micellar electrokinetic capillary chromatography ; Methylnitroanilines
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Computer-assisted procedures for the one-parameter optimization of the surfactant concentration and the concentration of urea or D-glucose as modifiers in micellar electrokinetic capillary chromatography have been developed. These procedures permit a rapid optimization of one parameter on the basis of only two experiments. Predicted values are compared to empirically obtained optimum values. The influence of the modifier concentration on the critical micelle concentration of sodium dodecyl sulfate was experimentally determined in buffers commonly employed in micellar electrokinetic chromatography. The alteration of retention factors of solutes caused by the influence of urea addition on the critical micelle concentration of sodium dodecyl sulfate was calculated under the assumption of constant distribution coefficients and compared to experimentally obtained values. It was demonstrated that the addition of urea or of D-glucose does not alter the phase ratio substantially.
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  • 58
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Protein separation ; Coated capillaries ; Repeatability of electroosmotic flow
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Capillary zone electrophoresis has been developed for the separation of seed albumins fromVicia faba using both uncoated and polyoxyethylene ether (Brij-35) coated octadecylsilane derivatized capillaries. Optimal separation conditions were found by studying the effect of pH, buffer composition and applied voltage. The nonionic surfactant/C18 coated capillary significantly reduced albumin adsorption and electroosmotic flow (EOF). A gradual washing out of the surfactant from the coated capillary during use altered not only the magnitude of the EOF, but also its reproducibility. The introduction of hydrophilic polymer solutions between analyses for dynamic modification of the Brij/C18 coated capillary surface prevented desorption of coating material, allowed optimization of resolution and ensured stability of the EOF. CE with surface-modified capillaries was then used to compare seed albumin profiles of severalVicia species. This technique appears to provide a powerful tool for use in taxonomic investigations.
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  • 59
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    Chromatographia 41 (1995), S. 389-392 
    ISSN: 1612-1112
    Keywords: Flavonols ; Capillary electrophoresis ; Temperature effects ; pH effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The use of capillary electrophoresis for the analysis of selected flavonols present in fruit juices and wines (kaempferol-3-rutinoside, rutin, avicularin, quercitrin, isoquercitrin, isorhamnetin, kaempferol and quercetin) was explored, and the effect of pH and temperature on the separation studied. The method had good reproducibility and analyses were carried out in less than 10 minutes.
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  • 60
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Enantiomer separation ; α-Cyclodextrin ; Chiral drugs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Enantiomer separation by capillary zone electrophoresis was studied for a set of 59 chiral drugs. With α-cyclodextrin as chiral solvating agent, six enantiomeric pairs could be resolved. Baseline separation was achieved for clidinium bromide, oxomemazine and tetryzoline, whereas ketamine, orphenadrine, tropicamide and others require further optimization. Aliphatic and monocyclic compounds prevail among compounds recognized by α-cyclodextrin. Statistical analysis reveals that a medium degree of migration retardation offers the best chance for successful separation.
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  • 61
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Column liquid chromatography ; Cefotaxime impurities ; Cross validation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A micellar electrokinetic chromatography method is presented which permits separation of cefotaxime and its major related impurities. Separation was carried out at 15 kV, using 30 mM sodium dihydrogen phosphate adjusted to pH 7.2 with 5 M NaOH and which contained 165 mM sodium dodecylsulfate as electrolyte. Results obtained by capillary electrophoresis were in good agreement with those of high-performance liquid chromatography with respect to the level of the major known impurities, total impurity content and cefotaxime purity.
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  • 62
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    Chromatographia 42 (1996), S. 263-268 
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Local anaesthetics ; Enantiomer separation ; Triethanolamine ; Dimethyl-β-cyclodextrin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A chiral capillary electrophoresis system for the highresolution separation of the enantiomers of the local anaesthetics mepivacaine, ropivacaine, bupivacaine and prilocaine is described. Triethanolamine was added to the background electrolyte to obtain a negative electroosmotic flow and hence higher resolutions. The interactions of the local anaesthetics and their chemical analogues with the chiral selector, dimethyl-β-cyclodextrin, were studied. From a model describing chiral capillary electrophoresis, the association equilibrium constants were determined by curve-fitting. The separation of mepivacaine, ropivacaine and bupivacaine was due to the different mobilities of the free analytes in solution, whereas the separation of a pair of enantiomers of a single analyte was due to differences between the association equilibrium constantsK 1 andK 2. Branching of the alkyl chain, which was situated close to the cavity in the inclusion complex, had strong effects on the chiral separation of the enantiomers.
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  • 63
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Molecularly imprinted polymer ; Enantioseparation ; Amino acids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A capillary electrophoresis method for the enantioseparation of D,L-aromatic amino acids using molecularly imprinted polymer as chiral selector has been developed. Methacrylic acid was used as functional monomer and ethylene glycol dimethacrylate (EDMA) as crosslinking monomer. The molecularly imprinted polymer was packed in capillaries by incorporating with acrylamide gel. The composition of the polymerization mixtures affects the separation factor to some extent. The molar ratio of cross-linker to functional monomer to print molecule was 20∶4∶1, which gives the best separation for aromatic amino acid enantiomers by using L-phenylalanine anilide (L-pheAN) as print molecule. Under the same conditions, however, separation of D,L-phenylalanine using L-phenylalanine as print molecule is poorer than that using L-pheAN. Polymer particles (≤5 μm) were supported by 6% acrylamide and 5% bisacrylamide gel in the capillary. The effects of organic solvents, electrophoretic buffer and pH on separation were also investigated.
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  • 64
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Organic acids ; Urine ; Neonates ; Lactate and Pyruvate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The determination of the organic acids oxalic, malonic, maleic, succinic, pyruvic, lactic, 3-hydroxybutyric and hippuric was investigated using capillary zone electrophoresis. They were separated in a fused-silica capillary (70 cm×75 μm id) which was filled with 50 mM sodium tetraborate (pH 10) containing a cationic surfactant as the electroosmotic flow modifier and Ca2+ in the buffer to aid separation of closely migrating peaks and improve peak shape. The developed method was successfully applied to the determination of organic acids in urine. The effect of passing samples through a C-18 solid phase extraction cartridge was investigated briefly, to try to simplify the sample prior to injection. Finally the developed screening procedure was used to study a set of urine samples some of which were obtained from children with metabolic errors resulting in the excretion of an abnormal organic acid profile. Discrimination between normal and abnormal samples was achieved. The results were in good agreement with information obtained by a GC-MS study of the same urine samples.
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  • 65
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Aminoglycosidic antibiotics ; DEAE-dextran ; Drugs ; Enantiomer separation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Diethylaminoethyl (DEAE) dextran hydrochloride and three kinds of aminoglycosidic antibiotics; fradiomycin sulfate, kanamycin sulfate and streptomycin sulfate, were employed as chiral selectors in capillary electrophoresis, enantiomer separation. These selectors are cationic or basic because of amino functionality and therefore used for enantiomer separation of acidic compounds. To avoid adsorption of the basic or cationic selectors on the capillary inner surface, a coated capillary was employed. Among those tested, enantiomers of binaphthyl compounds and synthetic intermediates of diltiazem analogues were separated. Methanol addition was effective for the improvement of peak shape and resolution.
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  • 66
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    Chromatographia 44 (1997), S. 5-9 
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Non-aqueous ; Water in organic solvents ; Selectivity ; Electroosmotic flow
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Water, in concentrations up to 10%, has been added to organic solvents (dimethylsulphoxide,N-methylformamide, acetonitrile and methanol) used as the buffer solvents in electrophoresis media for non-aqueous capillary electrophoresis. Anionic and cationic test substances have been used to study the effect on separation selectivity and efficiency. The effect on the electroosmotic flow has also been studied. Water added in concentrations up to 0.5% had only a minor effect on the separation selectivity, efficiency or electroosmotic flow in the systems studied. These results indicate that small variations in the water-content of organic solvents are of only minor importance to the reproducibility of non-aqueous capillary electrophoresis systems. The reproducibility of selectivity might, however, be slightly improved by adding 0.1–0.5% water, because true non-aqueous solvents are likely to cause problems as a result of the variable absorption of water.
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  • 67
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; On-line LC-CE ; Sample pretreatment ; Matrix effects ; Benzoic acids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Various methods are currently under investigation to improve concentration detection limits in capillary electrophoresis (CE). Stacking and isotachophoresis coupled in-line with free-solution electrophoresis are the techniques most frequently used. Samples containing a high and/or varying salt concentration, such as urine and serum, are difficult to handle: usually a significant loss in electrophoretic efficiency is observed compared with samples possessing a low electric conductivity. In the present paper an alternative approach is developed, i.e. a liquid chromatographic (LC)-type of sample pretreatment is coupled on-line with CE. To demonstrate the feasibility of this approach, the separation of three model compounds (benzoates) in water containing up to 400 mM of sodium chloride is studied using a 50 mM borate CE buffer of pH 9.5. The direct injection of samples with high salt concentrations in CE results in peak splitting and/or serious band broadening. These problems are not encountered when using the present LC-CE system. In addition, the detection limits are hardly influenced by the salt concentration of the sample; this underlines the robustness of the system.
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  • 68
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Enantiomer separations ; α1-acid glycoprotein ; Partial filling technique ; Basic drugs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Separation of the enantiomers of a variety of basic drugs by affinity capillary electrophoresis has been investigated using α1-acid glycoprotein (α1-AGP) as chiral selector. In order to use a high concentration of α1-AGP without causing low detection sensitivity, the partial filling technique was employed. Enantiomer separations were performed under conditions (a running buffer at pH 5.0 or 6.0) causing the protein to migrate toward the injection end. Twenty nine basic racemates were successfully separated by optimizing the protein concentration, buffer pH and organic modifier. α1-AGP obtained from three different suppliers was used to investigate differences among the proteins from different sources. Although most of the racemates were similarly separated with any of the three types of α1-AGP, some racemates, e.g. acebutolol behaved differently with the three types. The reasons for the different enantioselectivities of the three types of α1-AGP has not yet been clarified. The method was used to test the optical purity of commercial sulpiride enantiomers and it was found that the method was suitable and applicable for the purpose.
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  • 69
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Succinic and levulinic acid ; Indirect UV detection ; Standard addition method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary This paper describes an capillary electrophoresis (CE) method used to quantify both succinic acid and levulinic acid in an industrial production process. Measurement was performed by CE with indirect UV detection, using potassium hydrogen phthalate as the UV-absorbing additive. The electrolyte composition used was 5 mM potassium hydrogen phthalate at pH 7.0 containing 0.25 mM cetyl trimethylammonium bromide (CTAB) as an electrosmotic flow (EOF) modifier to reverse the EOF. The method provides for improved sensitivity by employing an extended path length capillary, and for identification and quantification by the use of a standard addition method.
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  • 70
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    Chromatographia 47 (1998), S. 219-224 
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Beta-blockers ; Protein separation ; Drug separation ; Guaran ; Buffer modifier
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Guaran, a neutral polysaccharide, has been used as a buffer modifier to improve the separation of basic proteins and drugs. Migration reproductibility, peak shape and efficiency were improved when 0.1% guaran was added to the buffer. The concentration of guaran, ionic strength, and pH of buffer solution were optimized to obtain the optimum separation of proteins. Possible separation efficiencies of 700,000 plates per meter were obtained for test proteins. The relative standard deviation (% RSD) of the migration time of all test proteins was less than 0.5%. Improved separation of β-blockers was also observed when guaran was added to the buffer.
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  • 71
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Drug purity ; Frequency doubled laser ; Laser induced fluorescence ; Reduced electromigration dispersion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary In drug purity determinations by capillary electrophoresis using UV-detection generally a relative high concentration of the main compound has to be injected. Principles how to handle overloading effects are described. NXX-066 is a drug with a native fluorescence which made it possible to use of CE system equipped with a LIF-detection unit. Monitoring drug purity determination with LIF detection results in an improved limit of quantification of the impurities and/or opens a possibility to avoid an overloaded main peak. A frequency doubled (FRED) argon ion laser set at 244 nm was used as excitation source in drug purity determination with the LIF-detection unit and the chemicals used were therefore carefully chosen in order to minimize the background noise level, which easily is enhanced when fluorescence detection is performed in the UV-range. The separation of the fluorescent NXX-066 analogues proved to be a difficult task, but an adequate resolution was obtained when β- and γ-cyclodextrins was added as structural selectors and the separation window was expanded by the use of a repressed/reversed electroosmotic flow. A comparison of the separation capability for the UV-detection system and the laser induced fluorescence detection system was performed, showing that the overloading effects of the main peak can be removed using the CE-LIF system and thereby obtain a substantially improved resolution of the analogues. A comparison of LC-UV and CE-UV for drug purity determination of a crude product from, synthesis of NXX-066 is also included in this paper where a good correlation of the results were obtained.
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  • 72
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; DNA fragments ; Cellulose derivatives ; Sieving cellulose matrix
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A rapid, robust and reproducible method providing excellent separation performance and simplicity using a 0.5% MC-4000 methyl cellulosic sieving medium in DB-1 coated capillaries has been developed. The method is suitable for qualitative comparison of DNA restriction profiles for fragments in the size range 100–1000 base pairs (bp). Efficiencies up to 8.5 million plates/m (1057 bp fragment) were recorded. Peak resolution of 6 bp (291/297 bp, 335/341 bp) and 4 bp (238/242 bp, 341/345 bp) was achieved. In addition, 1 bp partial resolution of 123/124 bp and 298/297 bp was obtained. Run-to-run (n=15), day-to-day (n=4), and capillary-to-capillary (n=3) variations of 0.1–0.2% RSD, 0.3–0.5% RSD, and 0.1–0.3% RSD, respectively, were observed. The MC-4000 sieving matrix was found to be better than hydroxypropyl methyl cellulose and hydroxypropyl cellulose, in terms of both performance and stability in the DB-1 coated capillaries. The efficiency and resolution in DB-WAX capillaries were inferior to those obtained in DB-1 capillaries. The commercially available DB-1 capillaries were stable for months in the sieving medium at pH 8.3 and could be regenerated to provide high efficiency after accidental current breaks.
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  • 73
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Ion chromatography ; Carbon disulphide in air ; Alkyl xanthogenates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A simple and sensitive method is presented for the measurement of carbon disulphide in air without interference from other gaseous sulphides. The procedure is based on the collection of CS2 in an ethanolic solution of KOH, where it is converted to potassium ethyl xanthogenate (PEX). The latter is determined by high-performance ion chromatography (HPIC) and/or capillary zone electrophoresis (CZE). Laboratory and field determination of detection limit, reproducibility and linearity, and specific advantages over other gas chromatographic and wet chemical methods, are discussed. Quantitative measurements of CS2 in air can be performed after sampling for 1 h with limits of detection as low as 15 ppb by HPIC and ca 0.1 ppm by CZE.
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  • 74
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    Chromatographia 48 (1998), S. 331-346 
    ISSN: 1612-1112
    Keywords: Peak integration ; Baseline determination ; Quantitation ; Capillary electrophoresis ; Chromatography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Peak integration is still a major source of error in analytical techniques such as chromatography (LC and GC), aapillary electrophoresis (CE), spectrosocpy, and electrochemistry. If the baseline is complex, e.g. because of matrix effects, or if the peak shape is irregular, e.g. because of peak tailing, the results are often not satisfactory when classical procedures are used. These shortcomings arise because of the stepwise appearance of the chromatogram. An algorithm that copies the human method of considering baseline and peaks as a whole has already been introduced. Here the use of a straight line as a baseline model led to an improvement in several instances. The baseline is, however, usually not exactly straight and rigid. A baseline model with flexible properties is more advantageous. Thus the smoothing cubic spline function is applied in this work. Here the rigidity can be controlled by use of a parameterp k. The prediction interval of the spline is used for iterative distinction between baseline and peak regions. Afterwards straightforward optimization of the peak boundaries is applied. More than 50 series of consecutive injections of the same sample (n=40 on average) were used to test the performance of this procedure. The same raw data have been integrated by means of the algorithm described here and by use of commercially available software. The reproducibility of the main component peak are within the series was taken as a measure of integration quality. Typically the new procedure reducesRSD % by approximately 33% (e.g. from 1.5% to 1.0%). The improvement is even more impressive for difficult samples with complex matrices, e.g. blood plasma or polymer excipients. for such samples improvements of up to a factor of 6 are obtained.
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  • 75
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Nonaqueous electrolytes ; N-Methylformamide ; UV-detection ; Pyridinyl-methyl-sulfinyl-benzimidazoles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A screening method using nonaqueous capillary electrophoresis (NACE) has been developed for purity analysis of pyridinyl-methyl-sulfinyl-benzimidazoles (PMSB). Eight different polar organic solvents were tested as background electrolytes.N-Methylformamide (NMF) was found to have the best properties in respect of both electrophoretic behavior and high solubility of five different model compounds. Optimization of the CE separation with regard to the effects of addition of various electrolyte modifiers is reported. An additional feature of amide solvents, rarely utilized in CE, is their intrinsic basic nature; this is of particular interest for analysis of compounds such as the PMSB, the degradation of which is acid-catalyzed. It is shown here that these compounds are stable at room temperature for weeks in NMF solution. Results from quantitative application of the NACE method were highly precise (typically 1.8%RSD for normalized peak area); linearity was good and detection limit in drug purity determination was low (∼0.05 area % relative to the drug compound).
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  • 76
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    Chromatographia 49 (1999), S. S73 
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Electrospray-ionization ; Mass spectrometry ; Orthogonal spray ; Peptides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Capillary electrophoresis (CE) with tandem UV and MS detection is increasingly being used for the analysis of complex mixtures. Here the analysis of peptides by CE-ESI-MS with a fully automated system is described.
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  • 77
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Chiral separation ; Neutral cyclodextrins ; Clorprenaline and other chiral drugs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Neutral cyclodextrin (CD)-modified capillary zone electrophoresis (CZE) has been applied to the chiral separation of four basic drugs— clorprenaline, benzhexol, esmolol and terazosin. Selector screening and concentration optimization experiments were performed. The resolution was 3.9 for clorprenaline, 2.3 for benzhexol, 3.1 for esmolol and 1.2 for terazosin when the running electrolyte was 60 mM hydroxypropyl-β-CD, 15 mM heptakis (2,3,6-Tri-O-methyl)-β-CD, 60 mM γ-CD and 60 mM heptakis (2,6-di-O-methyl)-β-CD, respectively, in 50 mM, pH 2.5 sodium phosphate buffer.
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