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  • Column liquid chromatography  (344)
  • Springer  (344)
  • American Meteorological Society
  • Blackwell Publishing Ltd
  • 1995-1999  (344)
  • 1965-1969
  • 1925-1929
Collection
Keywords
Publisher
  • Springer  (344)
  • American Meteorological Society
  • Blackwell Publishing Ltd
  • Wiley-Blackwell  (1)
Years
Year
  • 1
    Electronic Resource
    Electronic Resource
    Enantiomeric separation of trimetoquinol, denopamine and timepidium by capillary electrophoresis and HPLC and the application of capillary electrophoresis to the optical purity testing of the drugs (1995)
    Springer
    Chromatographia 40 (1995), S. 638-644 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02315130
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  • 2
    Electronic Resource
    Electronic Resource
    Effects of kinematic viscosity of the slurry on the packing efficiency of PEEK microbore columns for liquid chromatography (1995)
    Springer
    Chromatographia 40 (1995), S. 662-668 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Microbore columns ; Column packing ; Slurry viscosity ; Surfactants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The kinematic viscosity of the slurry used for the packing of microbore columns for liquid chromatography has been correlated with the packing efficiency. The columns were packed into polyetheretherketone (PEEK) tubing with an internal diameter of 0.5 mm using unbonded and bonded spherical silica gels under constant pressure conditions. Higher efficiencies were obtained using slurries suspended in aqueous solutions of surfactants, such as polyoxyethylene sorbitane monolaurte (Tween-20) and sodium dodecyl sulphate, in comparison with organic solvents usually used for column packing. The concentration dependencies of the relative kinematic viscosities of six slurries were compared using capillary viscometry. The slurries with low relative viscosities possessed rheological properties which enabled high packing densities, typical of a stable dense random packing arrangement, to be obtained at moderate packing pressures. The unusually low relative viscosities are discussed in terms of a “porous hydrodynamic bearing” model. The techniques used should also be generally applicable to the slurry packing of conventional columns.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02315134
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  • 3
    Electronic Resource
    Electronic Resource
    Quantitative structure-retention relationships for the investigation of the retention mechanism in high performance liquid chromatography using apolar eluent with a very low content of polar modifiers (1995)
    Springer
    Chromatographia 40 (1995), S. 690-696 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Structure vs. retention ; Principal component analysis ; Multiple linear regression ; Molecular descriptors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The mechanism of the retention in HPLC when using a non-polar solvent with a very low content of polar modifier as mobile phase is outside the scope of the classical interpretations. We have used quantitative structure-retention relationships (QSRR) to interpret the retention of a series of 36 compounds on 18 chromatographic systems (3 stationary phases and 6 mobile phases). Principal Component Analysis (PCA) was used to reduce the complexity of the data and to obtain the most significant axis; molecular modeling (molecular mechanics and molecular orbital calculations) was used to obtain structural information on the solutes, and multiple regression to correlate coordinates and descriptors. We have shown that the coordinates of the solutes on the first PCA axis are related to three molecular descriptors: the calculated logarithm of the partition coefficient in an octanol/water system (Log P), the polarisability (pol) and the energetic level of the highest occupied molecular orbital (HOMO). We have found the same equation with a similar coefficient for the three different stationary phases. These results prove the dominant role of the polar modifier in such chromatographic systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02315139
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  • 4
    Electronic Resource
    Electronic Resource
    Analysis of pyrithiones by reversed-phase high-performance liquid chromatography (1995)
    Springer
    Chromatographia 40 (1995), S. 669-673 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Transchelation ; Zinc pyrithione and related compounds ; Antidandruff formulations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An analytical procedure has been developed for the determination of zinc pyrithione in antidandruff formulations. Zinc pyrithione was converted into a stable copper complex and then analysed by reversed-phase HPLC. The proposed method allows the separation of the analyte from related pyrithiones and therefore is able to verify the compliance of cosmetic preparations with current legislation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02315135
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  • 5
    Electronic Resource
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    Determination of sugars by liquid chromatography and amperometric detection with a cuprous oxide modified electrode (1995)
    Springer
    Chromatographia 40 (1995), S. 684-689 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Sugars ; Amperometric detection ; Chemically modified electrodes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A chemically modified electrode was applied as a working electrode for the amperometric detection of sugars in liquid chromatography. A mixture of cuprous oxide and conductive carbon cement was used as electrode material. Cuprous oxide acted as a catalyst for the oxidation of sugars. Cyclic voltammetry was used to examine the oxidation of the sugars at the electrode surface. The stability and sensitivity of a cuprous oxide/conductive carbon cement (20/80 %, w/w) electrode were tested in flow injection analysis experiments. For liquid chromatography, sugars were separated on an ion-exclusion column with 0.01 M H2SO4 as mobile phase. After the separation, 0.2 M NaOH was added post-column and the sugars were determined at 550 mV vs. Ag/AgCl. Calibration was linear in the range of 10−6·10−3 M with limits of detection of approximately 1·10−6M. The application of the modified electrode for the determination of sugars in fruit beverages and dairy products following chromatographic separation is shown.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02315138
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  • 6
    Electronic Resource
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    An HPLC screening method for the detection of isonicotinic acid hydrazide in cattle milk (1995)
    Springer
    Chromatographia 40 (1995), S. 170-174 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Isoniazid in milk ; SPE preconcentration ; Diode array UV spectra
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A simple, fast, accurate and highly sensitive (5 ng/ml) method for the detection of sionicotinic acid hydrazide (isoniazid) in cattle milk is described, based upon an RP-HPLC system, equipped with a C18 column and a UV detector. Milk was deproteinized with trichloroacetic acid and treated with cinnamaldehyde, before being injected into the HPLC system. Preconcentration of samples on an SPE phenyl cartridge allows the sensitivity of the method to be increased to 0.05 ng/ml using a UV detector. The presence of isoniazid can be confirmed at concentrations as low as 0.4 ng/ml, through a diode-array UV spectrum of isoniazid hydrazone. The analytical procedure here described is routinely applied to investigate the illegal administration of isoniazid to cattle, as it provides a means of screening that can be carried out in a very short time.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02272167
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  • 7
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    Thermodynamic behavior of mixed benzodiazepines by a new liquid chromatographic method (1995)
    Springer
    Chromatographia 40 (1995), S. 193-196 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chemometric methodology ; Elution order ; Simplex optimization ; Benzodiazepines
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Using a rapid chemometric methodology to determine the separation factor, α, at different temperatures, Gibbs Helmholtz parameters (Δ (ΔH), Δ (ΔS), Δ (ΔG)) of two adjacent benodiazepines on a chromatogram were obtained from ln α versus T−1 plots. A temperature dependent reversal of the elution order was studied and the mobile phase composition and column temperature were optimized to obtain the best separation. A flow rate of 0.80 ml min−1 with 52.6% methanol in the methanol-water mixture and a column temperature of 48°C gave the most efficient separation of ten benzodiazepines.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02272170
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  • 8
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    Mixed-mode liquid chromatography of aliphatic anionic surfactants with a naphthalenetrisulfonate mobile phase (1995)
    Springer
    Chromatographia 40 (1995), S. 237-246 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Mixed mode stationary phases ; Indirect photometric and fluorometric detection ; Conductimetric detection ; Alkyl-sulphates, and sulphonat-phosphates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Separation of three classes of anionic surfactants (alkyl sulfates, alkanesulfonates, and alkyl phosphates) are achieved on a mixed-mode reversed phase (RP) phenyl/-anion exchange column using a naphthalenetrisulfonate (NTS)-acetonitrile (ACN) mobile phase via indirect photometric, indirect fluorometric, direct or indirect conductivity detection. Mixtures of C5−C18 sulfates, C6−C18 sulfonates, and C1−C4 phosphates (mono- and di-ester) can be separated in less than 20, 24, and 20 min respectively. Although hydrophobic effects are more pronounced in mixed-mode chromatography, equivalent-per-equivalent exchange of analysis and eluent ion is still required for sensitive indirect photometric, fluorometric, or conductivity detection. The detection limits of alkyl sulfates and alkanesulfonates are in the range of 3–15 pmoles which are at least an order of magnitude better than suppressed conductivity detection. The determination of surfactants in a variety of real samples is also presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02290352
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  • 9
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    Description of the retention behaviour of solutes in micellar liquid chromatography with organic modifiers: Comparison of two methods (1995)
    Springer
    Chromatographia 40 (1995), S. 279-286 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Micellar liquid phases ; Hybrid mobile phases ; Retention behaviour
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Two methods for the description of the retention behaviour of solutes in micellar liquid chromatography are compared. One of them divides the parameter space into triangular subspaces, fitting a different equation in each subspace. The second method makes use of a unique equation, valid in the whole parameter space. In both cases, equations of the type log k=f (μ, ϕ), and 1/k=f (μ, ϕ), (μ and ϕ are the concentration of surfactant and alcohol, respectively), were used to describe the retention. The use of the hyperbolic function, 1/k=c0+c1μ+c3μϕ, to describe the whole parameter space yielded the best prediction. When a small portion of the parameter space was modelled, a simpler hyperbolic function, lacking the μϕ term often led to good results. The logarithmic equations usually gave the poorer predictions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02290358
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  • 10
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    Prediction of precision from signal and noise measurement in liquid chromatography: Limit of detection (1995)
    Springer
    Chromatographia 41 (1995), S. 66-74 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Limit of detection ; Precision ; Uncertainty prediction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A method to determine the limit of detection (LOD) in high performance liquid chromatography (HPLC) is described. The power spectral density of instrumental baseline variation is fitted by the simplex least squares methods with a mixed random process of white noise and Markov process as a model. The white noise is characterized by standard deviation (SD), ∼w; the Markov process by the SD, ∼m, and auto-correlation degree, ρ. All required parameters for calculating the LOD signal are obtained by experiment without repeat measurements. No arbitrary constants are needed. The LOD signal is uniquely determined and is characterized by 33.3% relative standard deviation (RSD) of analyte measurements and 0.13% of the error of the first type. This signal also specifies that the signal-to-noise ratio=3, using the definition of noise originating from the white noise and Markov process. The theoretical conclusion is verified by the Monte Carlo simulation using real baseline and peaks. The LOD concentrations for naphthalene, acenaphthene, pyrene and perylene are given.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02274197
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  • 11
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    Reverse-phase liquid chromatography ofp-tert-butylcalixarenes (1995)
    Springer
    Chromatographia 41 (1995), S. 204-206 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; p-tert-Butylcalixarenes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Thep-tert-butylcalix[n]arenes (n=4,6,7,8) andp-tert-butyldihomooxacalix[4]arene have been separated by reverse phase liquid chromatography. Optimum conditions have been obtained on a Spherisorb ODS1, 5 μm C18 column by isocratic ambient elution with acetonitrile-methyltert-butyl ether. Calibration plots have been obtained from purified calixarenes and the reliability of the method is confirmed from test mixtures of calixarenes of known composition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02267956
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  • 12
    Electronic Resource
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    Supercritical fluid extraction-high performance liquid chromatography on-line coupling: Extraction of some model aromatic compounds (1995)
    Springer
    Chromatographia 41 (1995), S. 238-242 
    Details
    ISSN: 1612-1112
    Keywords: Supercritical fluid extraction ; Column liquid chromatography ; Aromatic compounds on silica
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An SFE-HPLC system has been tested with a simple model aromatic mixture on spiked silica. The spiked silica was extracted with pure CO2 and the extract retained in a trap packed with C18 material. Quantitative separation and reproducity have been investigated and are reported.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02267962
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  • 13
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    Signal enhancement by on-column fluorimetric detection in gradient elution of dansyl amino acids in liquid chromatography (1995)
    Springer
    Chromatographia 41 (1995), S. 148-152 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; On-column fluorimetric detection ; Gradient elution ; Dansyl amino acids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Fluorimetric detection in the presence of a stationary phase has been applied to gradient elution of dansyl amino acids in liquid chromatography. A 1.5 mm ID quartz tube packed with the same materials as the separation column was employed for the flow cell. Conventional-size columns were employed. The peak height of analytes increased with increasing retention owing to focusing and environmental effects of the stationary phase, leading to improvements in sensitivity, which was pronounced for analytes eluting late. The lower the gradient, the larger the improvement in sensitivity achieved. Detection limits were improved by a factor of up to 5.1 by fluorimetric detection using the packed flow cell, compared with those achieved using a common empty flow cell.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02267946
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  • 14
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    Simultaneous assay of four stereoisomers of diltiazem hydrochloride. Application to in vitro chiral inversion studies (1995)
    Springer
    Chromatographia 41 (1995), S. 450-454 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Diltiazem hydrochloride stereoisomers ; Chiralcel OF ; Chiral inversion ; Epimerization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The simultaneous stereospecific assay of four stereoisomers of diltiazem hydrochloride in bulk drug and aqueous solution was developed using HPLC on a Chiralcel OF column. The four isomers were quantitated with good precision by the internal standard method. The chiral inversion of (+)-cis-diltiazem hydrochloride in vitro, stability of its (2S, 3S) configuration in the solid and aqueous states was examined by HPLC. Chiral inversion of (+)-cis-diltiazem hydrochloride was not observed in the solid state, and its (2S, 3S) configuration was stable to heat, humidity and light. Chiral inversion of (+)-cis-diltiazem hydrochloride (2S, 3S) was observed in aqueous solution under UV, but not in aqueous solution stored at 80°C for 5h nor under visible light for 10 h. The (+)-cis-diltiazem hydrochloride (2S, 3S) epimerized to (+)-trans-diltiazem hydrochloride (2R, 3S) with a half-life of 5h in aqueous solution under UV but the reverse chiral inversion of (+)-trans-diltiazem hydrochloride (2R, 3S) to (+)-cis-diltiazem hydrochloride (2S, 3S) was not observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02318621
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  • 15
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    Detoxification of acetonitrile-water wastes from liquid chromatography (1995)
    Springer
    Chromatographia 41 (1995), S. 488-491 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Acetonitrile disposal ; Acetonitrile hydrolysis ; Degradation kinetics ; Waste solvent management
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Acetonitrile is one of the most frequently used solvents in column liquid chromatography. Because of its toxicity, safe disposal of the waste solvent is essential. Combustion in a hazardous waste plant, if available, is recommended. Otherwise the waste can be degraded in the laboratory to acetic acid and ammonia by treatment with sodium hydroxide. The addition of hydrogen peroxide is not necessary. The waste needs to be diluted to 10% acetonitrile in water in order to prevent the formation of a two-phase system on addition of concentrated sodium hydroxide. This reagent must be added in excess; 2.5 mols of sodium hydroxide per mol of acetonitrile are recommended. It was found that the kinetics are of second order, with an activation energy of 89 kJ mol−1 and a frequency factor of 9×109. Therefore even at room temperature degradation is possible, although a hydrolysis time of approximately 15 days is needed under these conditions. At 80°C, where refluxing is not necessary, hydrolysis is complete after, e.g., 2 h, depending on the amount of sodium hydroxide added.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02318626
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  • 16
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    Separation of saponins and determination of quinovic acid 3-O-α-L-rhamnopyranoside fromNauclea diderrichii (de Wild) Merr. Bark by high performance liquid chromatography (1995)
    Springer
    Chromatographia 41 (1995), S. 581-584 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Nauclea diderrichii (de Wild) Merr ; Saponins ; Alkaloid glycoside ; Chrysanthelline A
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A reversed-phase HPLC determination of 11 saponins and an alkaloid glycoside inNauclea diderrichii bark is described. Quantitative analysis of quinovic acid 3-O-α-L-rhamnopyranoside which is one of the main saponins was determined, using Chrysanthelline A as internal standard. The complete separation was achieved in 47 minutes. The method of quantification was validated.
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    URL: http://dx.doi.org/10.1007/BF02269723
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  • 17
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    Quantitative determination of toxic mono- and non-ortho polychlorinated biphenyls in cod liver oil after selective liquid chromatographic separation (1995)
    Springer
    Chromatographia 41 (1995), S. 585-593 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Column liquid chromatography ; Polychlorinated biphenyls ; Cod liver oil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary By application of a chromatographic column filled with Supelclean ENVI-Carb/Celite and elution with three solvents of different polarity three PCB fractions were obtained. Fraction A contained poly-ortho PCBs, Fraction B mono-ortho PCBs, and Fraction C non-ortho PCBs. The Supelclean ENVI-Carb/Celite column was used in combination with a sample preparation procedure for pre-cleaning of acid-stable chlorinated hydrocarbons such as DDT and its metabolites, HCH isomers, and regulation-relevant PCB congeners. The method was optimized using standard solutions of 55 PCB congeners, 8 chlorinated pesticides and contaminated cod liver oil samples. The influence of traces of remaining matrix on the elution profile of the organochlorine compounds on Supelclean ENVI-Carb/Celite was observed. Quantitation was carried out by GC-ECD with fused silica capillary columns of different polarity.
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    URL: http://dx.doi.org/10.1007/BF02269724
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  • 18
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    Study on the relationship between retention behavior and molecular structure parameters of substituted benzene derivatives in RPLC (1996)
    Springer
    Chromatographia 42 (1996), S. 43-48 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Substituted benzenes ; Solubility parameter ; Substituent constant
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A quantitative structure-retention model derived from the concept of hydrophobic substituent constant (π) and the total solubility parameter (δT) has been established. It has been used to predict successfully the retention behavior of a number of solutes on various columns in several different eluents. The experimental results indicate that the model can be employed for the prediction of retention of substituted benzenes in a large volume fraction range of mobile phase. In addition, the physical meaning of the sign and the influence of the coefficients of the model on the retention process had been discussed together with the dependence of these coefficients on the composition of mobile phase.
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    URL: http://dx.doi.org/10.1007/BF02271054
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  • 19
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    Analysis of contact allergenic compounds in oxidizedd-limonene (1996)
    Springer
    Chromatographia 42 (1996), S. 199-205 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Negative ion CI mass spectrometry ; Oxidizedd-limonene ; Contact allergenic compounds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A detailed chemical analysis and quantification of oxygen-containing monoterpenes in auto-oxidizedd-limonene was performed. Some of these, e.g. the cis- and trans-isomers of limonene-2-hydroperoxide, have previously been shown to exhibit strong contact allergenic properties. GC-MS with chemical ionization in negative ion mode was shown to be a successful method for the identification and determination of the molecular weight of chemically unstable limonene hydroperoxides. An HPLC method for isolation of individual compounds in auto-oxidizedd-limonene is presented. Two different stationary phases were used in normal phase mode, cyanopropyl- and diamino-modified silica. The method described can be used for the isolation of individual contact allergens in sensitization experiment vehicles, such as petrolatum and olive oil. This makes it possible to study whether test compounds, such as hydroperoxides, are chemically stable during a sensitization experiment.
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    URL: http://dx.doi.org/10.1007/BF02269653
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  • 20
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    Native and modified alumina, titania and zirconia in normal and reversed-phase high-performance liquid chromatography (1996)
    Springer
    Chromatographia 42 (1996), S. 217-222 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Stationary phases ; TiO2 ZrO2 AlO3 ; Separation of basic compounds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Chromatographic properties of silica, alumina, titania and zirconia have been investigated in normal phase mode in the separation of test mixtures of basic, neutral and acidic compounds. In contrast to silica the chromatographic behaviour revealed the basic properties of the alumina, titania and zirconia surfaces. Therefore, separation of basic compounds on these packings seems very promising. Lypophilic packings have been synthesized by modification of titania, zirconia and alumina with organosilanes and polymers and tested for the separation of basic compounds and proteins. High hydrolytic stability of the modified packings was observed during separations with strong alkali and acidic eluents.
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    URL: http://dx.doi.org/10.1007/BF02269656
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  • 21
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    Determination of ampicillin in New Zealand white rabbit plasma using column switching technique and HPLC (1996)
    Springer
    Chromatographia 42 (1996), S. 223-226 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Column-switching technique ; Rabbit plasma ; Ampicillin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The purpose of this study was to develop a simple and fast analytical method for quantitation of ampicillin in rabbit plasma, suitable for analysis of large numbers of samples collected from experimental animals. The concentration of ampicillin in rabbit plasma was determined utilizing ion-pair reverse-phase high performance liquid chromatography (HPLC) with UV detection and a column switching technique. Plasma samples were treated with a perchloric acid solution to precipitate proteins and centrifuged to pellet the precipitated proteins. Cephalexin was used as an internal standard. The C18 precolumn was placed in the injector loop of the Rheodyne injector. Samples were injected with the injector in the load position and the precolumn was washed free from interfering compounds. When the injector was switched to the inject position, the mobile phase was passed through the precolumn taking relatively pure compounds onto the analytical column. The limit of quantitation was established to be 400 ng mL−1 of plasma. The standard curves were linear over the range of ampicillin concentrations assayed, 400 to 10,000 ng mL−1 of rabbit plasma, and had a mean regression coefficient of 0.9962 (±0.0043). Intra-day variability was determined using six replicates of controls (low and high) analyzed on a single assay. The percent of relative accuracy for low and high controls were 5.67 and 1.12, respectively. Inter-day variability was determined over a four day period analyzing replicates of each control. The percent of relative accuracy for low and high controls were 4.33 and 1.63, respectively.
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    URL: http://dx.doi.org/10.1007/BF02269657
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    Separation and characterisation of hop bitter acids by HPLC-1H NMR coupling (1996)
    Springer
    Chromatographia 42 (1996), S. 499-505 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Hop bitter acids ; Supercritical fluid extraction ; On-line-1H NMR coupling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A supercritical carbon dioxide hop extract has been analysed using on-line coupling of high performance liquid chromatography (HPLC) with1H nuclear magnetic resonance (NMR) spectroscopy. For the first time high quality NMR spectra of the six major hop bitter acids were recorded by employing the stopped-flow detection mode. The resolution of the spectra obtained is similar to that of conventionally recorded spectra. All data are in agreement with the known structures.
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    URL: http://dx.doi.org/10.1007/BF02290283
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    A comparative study of the metal selective properties of chelating dye impregnated resins for the ion chromatographic separation of trace metals (1996)
    Springer
    Chromatographia 42 (1996), S. 528-538 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chelation ion chromatography ; Dye impregnated resins ; Trace metals in seawater
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary High-performance chelation ion chromatography (HPCIC) involving the use of chelating dye impregnated resins has been investigated for its ability to preconcentrate and separate a range of metals in a variety of complex samples. The parameters involved in the production of dye impregnated chelating columns have been identified and investigated. A number of selected chelating dyes have been impregnated into high-performance substrates, producing a range of chelating columns, exhibiting unique retention characteristics, dependent upon the nature of the impregnated chelating ligand. These columns have been classified in terms of retention characteristics, separation efficiency, dye loading and column capacity. A brief application of the above technique to the determination of Al (III) in seawater is illustrated.
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    URL: http://dx.doi.org/10.1007/BF02290287
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    Synthesis and chromatographic properties of HPLC chiral stationary phases based upon β-cyclodextrins (1996)
    Springer
    Chromatographia 42 (1996), S. 583-590 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chiral stationary phases ; Bonded cyclodextrins ; Reversed and normal mode separations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary β-cyclodextrin chiral stationary phases (CD-CSP) having different spacer lengths have been prepared and evaluated (retention, selectivity, resolution) for the liquid chromatographic separation of several series of enantiomers. The influence on the separations of the spacer length is discussed. The CD-CSPs were evaluated under normal and reversed mode conditions and the results compared with those from two commercial stationary phases containing β-cyclodextrin Chiradex and Cyclobond I.
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    URL: http://dx.doi.org/10.1007/BF02290296
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    Indirect liquid chromatographic determination of malathion based on copper(II) dimethyldithiophosphate complex formation (1996)
    Springer
    Chromatographia 42 (1996), S. 680-682 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Cu(II) dimethyldithiophosphate complex ; Malathion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A high-performance liquid chromatographic method has been developed for the quantitative determination of the organophosphorus pesticide malathion. The method is based on alkaline hydrolysis of malathion to dimthyldithiophosphate (DDTP) which is complexed with copper(II) and extracted in chlorofrom. The complex is injected onto a Hypersil ODS or Licrosorb sicolumn and eluted with acetonitrile:methanol:water (80∶10∶10 v:v:v) or chloroform. Detection is at 245 or 260 nm. A linear calibration curve was obtained for 24–240 μg ml−1 DDTP and a detection limit of 2.4–4.8 ng DDTP per injection. The method was applied to the analysis of malathion in commerical products after spraying on leaves. Extrction efficiency of malathion from leaves in acetone-water was also evlauted.
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    URL: http://dx.doi.org/10.1007/BF02267701
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    Gas and liquid chromatography and enzyme linked immuno sorbent assay in pesticide monitoring of surface water from the western mediterranean (Comunidad Valenciana, Spain) (1996)
    Springer
    Chromatographia 42 (1996), S. 151-158 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Column liquid chromatography ; Pesticide residues ; Surface water analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A monitoring programme based on gas chromatography (NPD, ECD) using MSD for confirmatory purposes and coupled-column liquid chromatography was applied to the analysis of pesticide residues in surface water from a predominantly agricultural area of Spain (Comunidad Valenciana). Samples analysed by means of enzyme-linked immunosorbent assay gave similar results to those obtained by GC (MSD) for the determination of total triazines. The test employed had the advantages of a simple test procedure, short analysis time and high confirmatory value. Nevertheless, the multiresidue character, accuracy and unequivocal identification of individual pesticide residues of GC (MSD) make this technique the most appropriate for environmental monitoring programmes. In this monitoring programme about 200 samples were analysed between 1993–1994. 27 different pesticides were detected in 91 of these samples. The pesticides more frequently detected were dimethoate, methidathion, endosulfan A and B, endosulfan sulphate and pirimicarb. The highest concentrations found were 39.9 μg L−1 of dimethoate, 10.6 of pirimicarb and 10.6 of methidathion.
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    URL: http://dx.doi.org/10.1007/BF02269645
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    Supported liquid membrane work-up in combination with liquid chromatography and electrochemical detection for the determination of chlorinated phenols in natural water samples (1996)
    Springer
    Chromatographia 42 (1996), S. 165-170 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Liquid membrane extraction ; Chlorinated phenols ; Natural water samples
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A sample preparation method has been developed for the determination of chlorinated phenols in water. The method is based on a supported liquid membrane extraction system connected on-line to liquid chromatography with electrochemical detection. The supported liquid membrane technique utilizes a porous PTFE membrane. The membrane is impregnated with an organic solvent which forms a barrier between two aqueous phases and enables selective extraction. The technique can easily be coupled in a flow system. In this investigation five chlorinated phenols (1–5 chlorine atoms) were extracted from natural water samples. Extraction for 30 minutes resulted in detection limits of approximately 25 ng L−1.
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    URL: http://dx.doi.org/10.1007/BF02269647
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    Sample size and retention values in gradient liquid chromatography of synthetic polymers (1996)
    Springer
    Chromatographia 42 (1996), S. 185-190 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Gradient elution of synthetic polymers ; Polystyrene and various styrene copolymers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Retention times in gradient liquid chromatography of synthetic polymers are often dependent on sample size. They increase with column load if the separation mechanism is governed by a solution process but decrease with increasing load if the mechanism is governed by adsorption. Since retention times independent of sample size are a prerequisite for peak identification as well as for the correct measurement of elution bands of samples with a broad distribution, measures to counteract sample-size effects deserve attention. Usually both solubility and adsorption are effective in gradient liquid chromatography of synthetic polymers. An appropriate balance of both effects is suitable for diminishing the influence of sample size on retention time of synthetic polymers. Ternary gradients allowing independent control of solubility and adsorption are promising.
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    URL: http://dx.doi.org/10.1007/BF02269651
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    Determination of nitrophenols, nitrobenzoic acids and polar explosives by HPLC-diode array detection in ground water samples of former ammunition plants (1996)
    Springer
    Chromatographia 43 (1996), S. 612-618 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Diode array detection ; Explosives residues ; Nitro-compounds ; Ground water ; Ammunition waste
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An HPLC method with diode array detection for the determination of acidic aromatic nitro compounds (in particular nitrophenols and nitrobenzoic acids) in ground water around former ammunition plants is presented. The use of an isocratic mobile phase, buffered to a pH of 2.30 on a reversed phase column, allows the separation of several nitrophenols and nitrobenzoic acids, some of which are known as phototransformation products of 2,4,6-trinitrotoluene (TNT). In a ground water sample from the former ammunition site at Elsnig (Saxony, Germany) 2,4- and 3,5-dinitrophenol (18), picric acid (8) and 2,4-dinitrobenzoic acid (3) were identified in addition to a variety of explosives determined previously. The presence of these compounds was corroborated by a diode-array (DAD)-library search.
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    H-point standard additions method for resolution of overlapped chromatographic peaks with a conventional fluorescence detector. Determination of phenol and cresols in waters (1996)
    Springer
    Chromatographia 42 (1996), S. 283-289 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Peak overlap ; Fluorescence detection ; H-Point standard additions method ; Water analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The H-Point Standard Additions Method (HPSAM) is proposed in order to resolve overlapping peaks in liquid chromatography by using a conventional fluorescence detector. The method uses as analytical signals the heights or the areas obtained at two previously selected emission wavelengths, and good results are obtained for highly overlapping peaks with highly overlapping fluorescence spectra. The principal benefits of the method are the ease of finding the required wavelengths, its insensitivity to changes in the retention time of the peak from one injection to another, and the possibility of using it in highly or only partially overlapping peaks. We have applied the method to the determination of phenol and cresols in water, resolving by the proposed method the overlapping peaks ofm- andp-cresol.
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    Identification of vitamin B12 analogues by liquid chromatography with electrothermal atomic absorption detection (1996)
    Springer
    Chromatographia 42 (1996), S. 566-570 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Electrothermal atomic absorption spectrometry ; Vitamin B12 analogues ; Cobalamins and cobalt ; Meat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The coupling of liquid chromatography and electrothermal atomic absorption spectrometry (LC-ETAAS) lowers the detection limit for identification of vitamin B12 analogues. Cobalamins and aqueous cobalt (II) were separated by reversed-phase liquid chromatography using a linear gradient: 26∶74 (v/v) methanol:0.05 M phosphate buffer (pH 4.2) to 50∶50 mixture over 8 min. The vitamins were quantitatively determined in the column effluent by measuring total cobalt by ETAAS. The analysis of meat and liver extracts by LC-ETAAS showed that the matrix did not interfere with the determination of cobalt. Hence, recoveries of cobalt in spiked meat and liver samples were satisfactory.
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    High-performance liquid chromatographic determination of meropenem in rat plasma using column-switching (1996)
    Springer
    Chromatographia 42 (1996), S. 405-408 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Meropenem in rat plasma ; Column-switching
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The purpose of this study was to develop a columnswitching HPLC method for the determination of meropenem in plasma. This method showed excellent precision and accuracy with good sensitivity and speed. The total analysis time per sample was less than 20 min and the mean coefficients of variation for intra- and inter-assay were less than 4.0%. The method has been successfully applied to plasma samples from rats receiving an intraperitoneal injection of meropenem.
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    URL: http://dx.doi.org/10.1007/BF02272131
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    HPLC determination of pesticides in green bean samples after SPE clean-up (1996)
    Springer
    Chromatographia 43 (1996), S. 265-270 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Diode array detection ; Solid-phase extraction (SPE) ; Pesticide analysis ; Multiresidue methods ; Green bean samples
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A reversed-phase high performance liquid chromatographic (HPLC) method with an acetonitrile-methanol-water mobile phase gradient and photodiode-array detection (DAD) is described for simultaneous determination of 21 pesticides, frequently used in agriculture, of different types, namely organophosphorus, organochlorine,N-methylcarbamates, triazines and phenylureas in vegetable samples. The pesticides were extracted with acetone and then partitioned from the vegetable sample with dichloromethane. Sample clean-up was accomplished by solid-phase extraction (SPE) using both C18 and florisil SPE columns. Average recoveries from green beans ranged from 70.0 to 110.1%. Detection limits of less than 0.1 mg kg−1 were obtained.
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    Determination of acidic chlorinated pesticides in water: Comparison of official EPA method 515.1 and liquid-solid extraction HPLC/UV and HPLC/PBMS analyses (1996)
    Springer
    Chromatographia 43 (1996), S. 279-284 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Column liquid chromatography ; ECD, UV and MS detection ; EPA Method 515.1 ; Chlorinated acidic pesticides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A comparison of the official EPA method 515.1 for determination of chlorinated acidic pesticides and a modification of it is illustrated. Extraction of the analytes from water and their determination and quantitation is by gas chromatography-electron capture detection (GC-ECD), liquid chromatography-UV detection and liquid chromatography-particle beam mass spectrometry. Although HPLC-PBMS was found to be less sensitive than the GC-ECD method, it was, nevertheless, more sensitive than HPLC-UV. The modified method is simpler, quicker and allows more accurate determination of pesticides in aqueous samples.
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    Extraction and identification procedures of polyphenolic compounds and carbohydrates in phillyrea (Phillyrea angustifolia L.) leaves (1996)
    Springer
    Chromatographia 42 (1996), S. 571-577 
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    ISSN: 1612-1112
    Keywords: Liquid-liquid and liquid-solid extractions ; Column liquid chromatography ; Mass spectrometry detection ; Flavonoids inPhillyrea angustifolia leaves
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Liquid-liquid (LLE) and liquid-solid extraction (LSE) procedures were developed to identify polyphenols in phillyrea (Phillyrea angustifolia L.) leaves. The liquidsolid extraction, carried out by using two serial Bond-Elut® CH and Bond-Elut® SAX cartridges allowed the collection of both polyphenols and soluble carbohydrates during a single extraction of leaf. This method seems to be suitable for both phytochemical and physiological study of the species, allowing the identification of two classes of organic compounds which have a central role in the metabolism of phillyrea plants. A method of isolation and concentration of polyphenols for further molecular characterization, using centrifuge chromatography, was also developed. Molecular characterization, carried out by UV-Vis spectrophotometry and mass spectrometry, demonstrated the presence of compounds with interesting biological activity, i.e. flavonoids and oleuropein derivatives. The soluble carbohydrate composition of phillyrea leaves did not substantially differ from that ofOlea europaea L. leaves, except for a higher mannitol/glucose ratio. This carbohydrate distribution may be linked to the evolution pattern of this species which usually grows in severely stressed environments.
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    Application of a new non-porous stationary phase (Kovasil-H) for the fast separation of peptides by HPLC (1996)
    Springer
    Chromatographia 42 (1996), S. 595-598 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Non-porous, reversed phase packing ; Fast peptide separation ; Peptide mapping
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Kovasil-H, a new 1.5 μm, non-porous, silica-based, reversed phase packing was investigated for the peptide mapping of Bovin Serum Albumin (BSA) and Cytochrome c tryptic digests and for the quality control of trypsin. Using short columns (33–66 mm) and high temperature, very short analysis times and high sensitivities were attained. No special modification of commonly used liquid chromatographs are necessary for the application of this method.
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    Chromatographic determination of caffeine in pharmaceutical formulations using micellar mobile phases (1996)
    Springer
    Chromatographia 43 (1996), S. 149-152 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Caffeine ; Pharmaceutical formulations ; Micellar liquid chromatography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An HPLC procedure is described for the determination of caffeine in pharmaceutical preparations. A Spherisorb octadecylsilane ODS-2 C18 analytical column and spectrophotometric detection at 273 nm were used. The chromatographic behaviour of caffeine with different micellar eluents containing sodium dodecyl sulphate (SDS) is described. The determination of caffeine in pharmaceutical preparations was performed by use of a mobile phase containing 0.05 M sodium dodecylsulphate (SDS) and 1.5% propanol at pH7. At a 6.0 μg mL−1 concentration level the peak area and peak height repeatability were 2.6 and 2.4%, respectively. The application of the proposed method to the analysis of five pharmaceutical formulations, using peak heights as the dependent variable, gave recoveries between 85 and 104% of the values declared by the manufacturers. The proposed procedure for the determination of caffeine is rapid (15 min per sample), reliable and free from interferences.
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    Evaluation of the influence of the base material loaded with hydrous zirconium oxide gel on the retention behavior of disubstituted benzoic acids (1996)
    Springer
    Chromatographia 43 (1996), S. 79-81 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Hydrous zirconium oxide ; Porous polymer resin ; Silica gel ; ortho-Benzoic acid derivatives
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Silica gel loaded with hydrous zirconium oxide (Zr-gel-S) has been prepared and the influence of the base material on the retention behavior ofo-phthalic acid on the hydrous zirconium oxide was evaluated. The retention behavior of the acid on the Zr-gel-S was compared with that on Zr-gel-5, the polymer-based Zr-gel. Comparable retention behavior,i.e. maximum retention in the vicinity of pH 6, which has been regarded as the equal adsorbic point, was observed for both types of Zr-gel, although there was a large difference in the retention times. The difference in retention on the two types of Zr-gel could be ascribed to nature of the base material. The results in this experiments showed, however, that the specific behavior at pH 6 was an essential characteristic of hydrous zirconium oxide and was not related to the influence of the base materials.
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    Retention on Diol column—A case study (1996)
    Springer
    Chromatographia 43 (1996), S. 436-438 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Diol columns ; Optimisation ; Ephedrine ; Synopen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The effect of simultaneous variation of buffer pH, molarity and organic modifier concentration when Diol stationary phase is used was experimentally studied. An equation has been derived for the retention time in the interpolation region of ephedrine and synopen—principal active components in an antihistamine formulation.
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    Polycyclic aromatic hydrocarbons in waste waters and sewage sludge: Extraction and clean-up for HPLC analysis with fluorescence detection (1996)
    Springer
    Chromatographia 43 (1996), S. 135-142 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Polycyclic aromatic hydrocarbons ; Waste waters ; Sewage sludge
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A modified solid-phase extraction technique using sonication of the adsorbent material instead of the elution normally applied has been compared with two conventional liquid-liquid extraction procedures for the determination of the 16 EPA PAHs in municipal waste waters by means of HPLC coupled with fluorescence detection. Liquid-liquid extraction with cyclohexane proved to be the most efficient and simplest procedure. Clean-up of the waste-water extracts was not considered necessary, because of the high chromatographic resolution of the column and the selectivity of the fluorescence detector. Different organic solvents were also compared for ultrasonic extraction of PAHs from sewage sludge. The best results were obtained by use of acetonitrile. Clean-up of sewage-sludge extracts was not found necessary for accurate quantification of the major PAH components with fluorescence detection. The precision of the whole analytical procedure from extraction to the final determination of PAHs was satisfactory for both waste-water and sewage-sludge samples.
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    Optimization of alkali-alkalkine earth cation separation on weak cation-exchangers (1996)
    Springer
    Chromatographia 43 (1996), S. 117-123 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ion-exchange chromatography ; Ion-exchange mechanism ; Optimization of alkali and alkaline earth separation ; Crown ether complexing reagents
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The elution behavior of alkali and earth alkaline cations has been studied on a newly synthesized weak cationexchanger (WCX). Applying this stationary phase isocratic separation of these cations is possible. The dependence of retention on competing ion concentration is described via a simple model. The influence of crown ethers as well as organic eluent additives on selectivity and peak efficiency is demonstrated. With optimized separation such cations can be determined with detection limits of about 0.5 ppm using a conductivity detector without ion suppression.
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    Selectivity of dansyl amino acids in micellar liquid chromatography with an ion-exchange-induced stationary phase (1996)
    Springer
    Chromatographia 43 (1996), S. 143-148 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Micellar liquid chromatography ; Ion-exchange-induced stationary phase ; Dansyl amino acids (Dns-AAs) ; Fluorescence enhancement
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The retention behavior of dansyl amino acids in micellar liquid chromatography has been examined by using ionexchange-induced stationary phases. Several parameters affected the retention of the analytes, including the type and concentration of micellar agent and modifier ion and the concentration of acetonitrile in the mobile phase. The order of elution of dansyl amino acids obtained with the micellar mobile phase was very different from that observed in conventional reversed-phase liquid chromatography. Fluorescence intensities of some dansyl amino acids were enhanced by the micellar mobile phase.
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    High performance liquid chromatography of disaccharides on a porous graphitic carbon column applying post-column derivatization with benzamidine (1996)
    Springer
    Chromatographia 43 (1996), S. 254-260 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Carbohydrates ; Anomer separations ; Post-column derivatization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A sensitive post-column fluoresence method based on the reaction of reducing sugars with a fluorigenic reagent (benzamidine) under alkaline conditions and elevated temperature is described. Optimum reaction conditions suitable for the detection of fluorescent reaction products have been investigated. A porous graphitized carbon column (shandon Hypercarb) was employed as the chromatographic solid phase and elution was isocratic by an aqueous acetonitrile mixture. A special problem in sugar analysis is the tendendy of anomer formation giving doublet peaks. This tendency varies largely among the different sugars, and systematic studies on conditions that eliminate this problem were performed. Efficient and selective separations of a series of disaccharides were obtained using high temperatures and a low concentration of acetonitrile in the mobile phase. The detection limits (S/N=3) with an injection volume of 20 μL ranged from 10–60 picomoles. Linear calibration graphs were obtained in the 2–20 μM concentration range (r 2〉0.99). A relative standard deviation between 1–3% (n=6) demonstrated good precision of the developed system.
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    Amino acid analysis by derivatization with chromogenic 4-phenylazobenzyloxycarbonyl chloride (PAZ-Cl): Comparison of reversed-phases (1996)
    Springer
    Chromatographia 43 (1996), S. 275-278 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chromogenic reagent ; Chloroformate ; Pre-column derivatization ; Amino acids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The chromogenic reagent 4-phenylazobenzyloxycarbonyl chloride (PAZ-Cl) was used for the automated pre-column derivatization of amino acids (AAs) at ambient temperature followed by liquid chromatographic separation of the derivatives formed. Since in previous investigations it was realised that the selectivity of a C-18 stationary phase decreased after 40 injections of PAZ-AAs the suitability of 12 reversedphases distinguished by silica modification, carbon content, and particle characteristics was tested. Among these columns only a polymer-coated C-18 stationary phase furnished satisfactory repeatability of retention times for 250 analyses.
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    Identification of the [(bpy)2Ru(Im)(H2O)]2+ complex as an reaction intermediate by reversed-phase high-performance liquid chromatography (1996)
    Springer
    Chromatographia 43 (1996), S. 322-326 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ruthenium diimine complexes ; Inorganic synthesis ; Kinetics monitoring
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The synthesis of the complex [(bpy)2Ru(Im)2]2+ (bpy=2,2′-bipyridine; Im=imidazole) has been monitored by reversed-phase HPLC. The analytical results obtained during the reaction have shown that it is feasible to identify and isolate the [(bpy)2RuIm(H2O)]2+ complex as a reaction intermediate. The optimization of the synthetic procedures for these two species has been established and the compounds have been obtained in high purity. The use of HPLC has enabled complete analytical control of the synthesis of the [(bpy)2RuL2]2+ class of compounds, enabling the identification of reaction intermediates.
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    Preparation and separation of metallobacteriochlorophylla by reversed-phase high-performance liquid chromatography (1996)
    Springer
    Chromatographia 43 (1996), S. 361-364 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Bacteriochlorophylla ; Copper(II) bacteriochlorophylla ; Zinc(II) bacteriochlorophylla
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Semi-preparative high-performance liquid chromatography has been used for the preparation of copper(II) bacteriochlorophylla [Cu(II)-BChl-a] and zinc(II) bacteriochlorophylla [Zn(II)-BChl-a]. Both compounds are separated on a reversed-phase Inertsil ODS-2 column using a mobile phase of acetone-methanol (25∶75, v/v). The fractionated metallobacteriochlorophylls (M-Bchl-a) are identified by fast atom bombardment mass spectrometry. The spectroscopic parameters such as the wavelength of absorption maxima and the molar extinction coefficients are determined using pure M-Bchl-a obtained by preparative HPLC. The HPLC method proposed here has been demonstrated to be useful for the purification and determination of components of M-Bchl-a.
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    Assay of four stereoisomers of desacetyl diltiazem hydrochloride. Application toin vitro chiral inversion studies (1996)
    Springer
    Chromatographia 43 (1996), S. 413-418 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Desacetyl diltiazem hydrochloride stereoisomers ; Chiralcel OF ; Chiral inversion ; Epimerization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Direct resolution of four stereoisomers of the related compound of diltiazem hydrochloride, namely desacetyl diltiazem hydrochloride, was studied by both normal and reversed-phase chiral HPLC. The four stereoisomers were completely resolved on a Chiralcel OF column. The technique developed was applied to a chiral inversion study of desacetyl diltiazem hydrochloride. This inversion was observed neither in the solid state, in aqueous solution at 100°C for 3 h nor under visible light for 10h, but was observed in aqueous solution under UV irradiation. The (+)-(2S, 3S)-cis-desacetyl diltiazem hydrochloride degraded with a half-life of 1.9 h in aqueous solution under UV and epimerized to (+)-(2R, 3S)-trans-desacetyl diltiazem hydrochloride. Similarly, (+)-(2S, 3S)-cis-desacetyl diltiazem hydrochloride degraded about three times faster than diltiazem hydrochloride. Reverse epimerization of (+)-(2R, 3S)-trans-desacetyl diltiazem hydrochloride to (+)-(2S, 3S)-cis-desacetyl diltiazem hydrochloride was not observed. The overall degradation was the result of two competitive processes, the epimerization and the decomposition of the benzothiazepin ring. The degradation and epimerization rate of (+)-(2S, 3S)-cis-desacetyl diltiazem hydrochloride in solution under UV depended upon the solvent, the aqueous pH, and concentration.
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    Simultaneous determination of triprolidine, pseudoephedrine, paracetamol and dextromethorphan by HPLC (1996)
    Springer
    Chromatographia 43 (1996), S. 496-500 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Pharmaceutical formulations ; Triprolidine ; Pseudoephedrine ; Paracetamol ; Dextromethorphan
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A simple, rapid and specific HPLC method has been developed for the determination of triprolidine, pseudoephedrine, paracetamol and dextromethorphan, in combination, in different pharmaceutical dosage forms, using a reversed-phase C18 column, gradient elution, and UV detection at 254 and 280 nm. No preliminary extraction procedure is required for liquid formulations and a very simple extraction procedure is required for tablets and creams. The recovery of the drugs ranged from 96.0 to 98.7%. The assay results obtained for eight commercially available formulations were in agreement with the amounts declared. The linearity and precision of the method have been assessed.
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    Determination of free aliphatic aldehydes in plasma by high-performance liquid chromatography of the 1,3-cyclohexanedione derivatives (1996)
    Springer
    Chromatographia 43 (1996), S. 501-506 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Aldehydes, aliphatic ; 1,3-Cyclohexanedione (CHD) ; Fluorimetric detection ; Plasma analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A simple and sensitive method is proposed for the measurement of aldehydes in plasma. The plasma samples are treated with 1,3-cyclohexanedione (CHD) and after addition of the internal standard (the CHD derivative of octaldehyde) are analysed by reversed-phase high-performance liquid chromatography with an acetonitrile-water gradient as the mobile phase. Detection is by fluorimetry with excitation at 395 nm and emission at 457 nm. In plasma samples spiked with aldehydes, the calibration curves showed good linearity in the range 0–10 μg mL−1. The recoveries of aldehydes were quantitative; coefficients of within-day and between-day variation were less than 13% and 11%, respectively. Applications to human and some animal plasma samples are reported.
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    Synthesis and characterization of titania based stationary phases using the silanization/hydrosilation method (1997)
    Springer
    Chromatographia 44 (1997), S. 538-544 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Octadecyl titania ; Hydride surface ; Hydrosilation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The silanization/hydrosilation bonding method is tested on both a laboratory synthesized and commercial titania. The laboratory titania made by the sol-gel process shows evidence of residual organic material that is removed by an initial acid hydolysis followed by bonding of the hydride (triethoxysilane) under acidic conditions. DRIFT and solid state CP-MAS NMR studies are used to confirm the formation of the hydride layer on the titania and the success of the hydrosilation process for attaching an organic moiety (1-octadecene) to the surface. Chromatographic testing, primarily on the commercial titania based C-18 phase, indicates good reverse phase properties and few residual OH groups, either Ti−OH or Si−OH, as determined by the symmetrical peak shapes obtained for anilines and alkylphenylamines using mobile phases with no buffers or masking agents in the aqueous component.
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    Interactions between cisplatin derivatives and mobile phase during chromatographic separation (1997)
    Springer
    Chromatographia 44 (1997), S. 19-24 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Cisplatin stability ; Cisplatin metabolites ; Platinum phosphato-derivatives
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Althoughcis-dichlorodiammineplatinum(II) (cisplatin or CDDP) is widely used for the treatment of several kinds of tumour, its stability and metabolism in biological fluids have not been completely elucidated. Conditions in which mobile phases of formic or phosphoric acids interact with platinum derivatives during chromatographic separation performed by high performance liquid chromatography on-line with inductively coupled plasma-mass spectrometry (ICPMS) are investigated. During chromatographic separation of CDDP the formic acid mobile phase does not interact with CDDP itself nor with its hydrolysis products. In contrast, the phosphoric acid mobile phase interacts, not with the CDDP itself, but with its hydrolysis products which are present only in an aged aqueous solution, to generate two platinum phosphato-derivatives. This study suggests that the phosphoric acid has greater affinity for the CDDP hydrated complexes than formic acid and the latter is more appropriate for the study of cisplatin behavior in aqueous and biological media.
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    Reversed-phase high-performance liquid chromatographic separation of mono- and divinyl chlorophyll forms using pyridine-containing mobile phases and a polymeric octadecylsilica column (1997)
    Springer
    Chromatographia 44 (1997), S. 43-49 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Mono-and divinyl chlorophylls ; Polymeric ODS phases ; Pyridine containing mobile phases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The separation of chlorophyll forms was studied employing a wide bore polymeric octadecylsilica column and pyridine containing mobile phases, giving consideration to considering the influence of mobile phase composition and column temperature on the resolution of monovinyl forms from their divinyl analogues. A method involving gradient elution and operating at 15°C is proposed for the separation of several polar and non-polar mono- and divinyl chlorophylls from etiolated tissues of higher plants and from marine phytoplankton. The advantages of pyridine as a mobile phase additive in the reversed-phase liquid chromatography of chlorophylls are discussed.
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    Optimisation of chromatographic separations by use of a chromatographic response function, empirical modelling and multivariate analysis (1997)
    Springer
    Chromatographia 44 (1997), S. 74-80 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chiral separation ; Optimisation ; Multiple linear regression ; Neural networks
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The chiral separation of the drug substance R,S-oxybutynin chloride on a reversed phase HPLC system has been optimised by use of empirical modelling and multivariate analysis. The separation was characterised by a new chromatographic response function developed to modulate both quality of separation and retention time. The study includes a comparison between three different multivariate techniques (multi-layer feed-for-ward neural networks, multiple linear regression and partial least squares regression) of their capabilities to model the new chromatographic response function and predict its value for new experiments. It was indicated that the most accurate models were achieved with neural networks, although partial least squares regression could also be used to solve the problem since it gives the major directions for the optimal settings of the variables.
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    URL: http://dx.doi.org/10.1007/BF02466519
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    Retention behavior of morphine and its metabolites on a porous graphitic carbon column (1998)
    Springer
    Chromatographia 47 (1998), S. 667-672 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Porous graphitic carbon ; Optimization ; Morphine and metabolites
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The chromatographic behaviour of a series of morphine-based opiates has been investigated using a porous graphitic carbon packing material at acid and alkaline pH. The effects of mobile phase pH, mobile phase organic percentage, column temperature and ionpairing agents were studied. All six opiates were separated within a close retention window despite large differences in measured lipophilicities of the individual opiates. The retention order was not related to the log P values of the opiates and strong retention of the fully ionised compounds was observed, particularly those with acidic functional groups. The effect of pH on the retention of the compounds indicated that the degree of ionisation of the individual compounds was important in the separation mechanism, suggesting that hydrophobic interactions were present in addition to the polar retentive effects observed above. The strong retention of the ionised glucuronide and sulphate conjugates of morphine is a particularly useful feature of the porous graphitic carbon packing material which has general applicability to the analysis of polar or ionised drug metabolites.
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    An exprimental design approach to selecting the optimum liquid chromatographic conditions for the determination of vitamins B1, B2-phosphate, B3, B6 and C in effervescent tablets containing saccharin and sunset yellow FCF (1997)
    Springer
    Chromatographia 44 (1997), S. 634-644 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Vitamin B and C in tablets ; Experimental design ; Optimization of separation ; Multiple regression modeling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The ion-pair liquid-chromatographic separation of the water-soluble vitamins thiamine mononitrate, riboflavin phosphate, nicotinamide, pyridoxine hydrochloride, ascorbic acid, saccharin, and the dye Sunset Yellow FCF (E110) has been examined for the analysis of the compounds in effervescent tablets. A Draper-Lin small composite design was used to study the impact on the compounds' retention times and peak-widths (the response variables) of four different mobile phase variables: percentage of methanol as organic modifier, the concentrations of hexanesulfonate as ion pairing reagent and of triethanolamine as competitive base, and pH. The interactions of these variables were also studied. The proposed design enabled derivation of multiple linear regression equations to model each compound's retention time and peak-width at half-height. The statistical reliability of the regression models was established by comparing predicted and experimental values. By introducing the regression models into a spreadsheet program (Excel 5.0), retention times and peak-widths for each compound were calculated at fixed mobile phase pH. The values of all the other combinations of the three mobile phase variables were changed in increments of two units within their examined boundaries, resulting in 225 different rows. For each combination the compounds' calculated retention times and their corresponding peak-widths were sorted in increasing order and the resolution between successive peaks was calculated. The minimum effective resolution (R s min) between each pair of peaks and the maximum retention time (t R max) in each row were then selected and used to construct contour plots indicating the location of zones of mobile phase parameter combinations whereR s min〉1.5 and the analysis was rugged, and wheret R max values were minimum. Their common regions resulted in optimum chromatographic separations. Examples are shown of chromatographic separations obtained using mobile phase combinations which were the best compromise of the three criteria selected.
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    Interlaboratory study of analysis of phenoxymethylpenicillin by liquid chromatography (1998)
    Springer
    Chromatographia 47 (1998), S. 152-156 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Phenoxymethylpenicillin ; Collaborative study
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A liquid chromatography method for analysis of phenoxymethylpenicillin has been examined in a collaborative study involving 6 laboratories. The method comprised an isocratic part, which is used in the assay. When the isocratic part is combined with gradient elution, the method is suitable for purity control. Five samples of phenoxymethylpenicillin (potassium salts and acid) were analysed. The main component, the most important side product 4-hydroxyphenoxymethyl-penicillin and other impurities were determined. An analysis of variance proved the absence of consistent laboratory bias. Laboratory-sample interaction was not significant. Estimates of the repeatability and reproducibility of the method, expressed as standard deviations (SD) of the result of the determination of phenoxymethylpenicillin, were 0.50 and 0.63 respectively.
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    Bile acids as stationary phase in liquid chromatography (1998)
    Springer
    Chromatographia 47 (1998), S. 183-188 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Bile acid aggregates as stationary phase ; Enantiomeric separation ; 1,1′-Binaphthyl-2,2′-diyl-hydrogenphosphate enantiomers ; Dansyl amino acids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Bile acids chemically bonded onto aminopropylsilica have been employed as stationary phases in liquid chromatography. Bile acid aggregates were dynamically formed around molecules chemically anchored on the supports when the eluent contained bile salts. The bile salt aggregates achieved the separation of 1,1′-binaphthyl-2,2′-diyl-hydrogenphosphate enantiomers and dansyl amino acids.
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    Determination of clozapine in human plasma by solid-phase extraction and liquid chromatography with amperometric detection (1998)
    Springer
    Chromatographia 47 (1998), S. 8-12 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Amperometric detection ; Solid-phase extraction ; Plasma ; Clozapine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A sensitive and selective high-performance liquid chromatographic method has been developed for monitoring clozapine levels in human plasma. Chromatography was performed on a reversed-phase column (C8, 150 mm×4.6 mm i.d., 5 μm) with acetonitrile-aqueous sodium acetate solution, 88∶12 (v/v), as mobile phase; the flow rate was 1 mL min−1. Clozapine oxidation at +800 mV was detected amperometrically. Response was linearly dependent on concentration over the range 50–1500 ng mL−1 clozapine in plasma. Sample preparation by solid-phase extraction before HPLC analysis gave high extraction yield (94%). The accuracy and precision of the method were both very good (recovery: 97%;RSD〈3.3%).
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    Retention study on silica gel in high-temperature liquid chromatography (HTLC) (1998)
    Springer
    Chromatographia 47 (1998), S. 278-284 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; High-temperature columns ; Retention behavior ; Column equilibration ; Bilayer formation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Retention volumes (V N) of different kinds of test compound have been measured on silica gel as a function of column temperature (T) in the range 20 to 210°C.n-Heptane and mixtures ofn-heptane and polar modifiers were used as mobile phases. With nC7 and nC7-1,4-dioxane mixtures, there was a good linear relationship between InV N and 1/T for column temperatures above 100 °C. When more polar modifiers such as butanol, ethanol and acetic acid were used, ‘N’-shaped curves were obtained for the plots of InV N against 1/T. Possible explanations of this retention behavior have been proposed on the basis of related studies and common physical chemistry relationships. Column equilibration time after alteration of water content or column temperature is greatly reduced at elevated temperatures. This will benefit the application of LSC on silica gel.
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    Ligand-exchange chromatographic separation of DL-amino acids on aminopropylsilica-bonded chirals-triazines (1998)
    Springer
    Chromatographia 47 (1998), S. 637-642 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ligand-exchange chromatography ; Chiral stationary phases ; Enantiomer separation ; Amino acids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Chiral stationary phases (CSPs) were synthesized by reaction of aminopropylsilica (APS) with chiral monochloro-s-triazines (MCTs). MCTs were obtained by reaction of 2,4,6-trichloro-s-triazine (cyanuric chloride) with one equivalent of methanol and, subsequently, with one equivalent of L-prolinetert butyl ester (H-Pro-OtBu) orN-tert butyloxycarbonyl-L-lysinetert butyl ester (Boc-Lys-OtBu). End-capping of unreacted amino groups of APS with acetic anhydride, followed by trifluoroacetolytic cleavage of the protecting groups of amino acids (AAs), afforded two chiral stationary phases bearing either L-proline (CSP-3) or L-lysine (CSP-4) as chiral selector. Using ligand-exchange chromatography matography with addition of Cu2+ to the mobile phase, enantiomers of free DL-AAs and a fewN-(2,4-dinitrophenyl)-DL-AAs were separated on CSP-3, whereasN-(dansyl)-DL-AAs were separated on CSP-4.
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    Determination of glucuronides of molecules of toxicological interest by liquid chromatography negative-ion mass spectrometry with atmospheric pressure chemical ionization (1998)
    Springer
    Chromatographia 47 (1998), S. 659-666 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Atmopheric Pressure Chemical Ionization (APCI) mass ; spectrometry ; Glucuronide-conjugates ; Toxicological compounds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A new chromatographic method for the direct determination of metabolites (glucuronide-conjugates) of molecules of toxicological relevance in biological media with the minimum sample pre-treatment has been developed. A high performance liquid chromatographyatmospheric pressure chemical ionization-mass spectrometry (LC-APCI-MS) system was used for this purpose. The separation of four glucuronides Aminophenylglucuronide (APhG), Phenylglucuronide (PhG),p-Nitrophenylglucuronide (NPhG) and α-Naphthylglucuronide (NG) was obtained under ion-suppressed reversed-phase chromatography conditions, by using high-speed (3 cm, 3 μm) columns and formic acid (2 mM) as the acid modifier in the mobile phase. Different C-18 stationary phases (partially endcapped and non-endcapped) were evaluated in order to obtain retention for these very polar, water soluble molecules. The ionization of the analytes was obtained in negativeion (NI) mode. Detection limits were in the range 1–5 mg L−1 and calibration curves were linear over two order of magnitude. Intra-day and inter-day precision were in the range 2.9–10.6% for all the compounds. The method was successfully applied for the determination of PhG in a urine sample of a European Quality Assurance Programme for Organic Solvent Metabolites.
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    Direct solid-phase microextraction combined with gas and liquid chromatography for the determination of lidocaine in human urine (1998)
    Springer
    Chromatographia 47 (1998), S. 678-684 
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    ISSN: 1612-1112
    Keywords: Gas chromatography ; Column liquid chromatography ; Solid-phase microextraction ; Local anaesthetic lidocaine ; Optimisation of extraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Solid-phase microextraction (SPME) has been combined with gas chromatography (GC) and liquid chromatography (LC) for the determination of lidocaine in human urine. A polydimethylsiloxane (PDMS) coated fibre was directly immersed into buffered urine. Extraction conditions such as time, pH, ionic strength, temperature, and agitation were optimised. The extracted lidocaine was thermally desorbed in a split/splitless injector for analysis with a GC-FID system or desorbed with liquid in a specially designed SPME-LC interface for analysis with an LC-UV system. After optimisation the method developed was evaluated and validated. Extraction yields of 22% were obtained in about 45 min. The reproducibility of the method is 〈5% (relative standard deviation). For five-times diluted urine, linear ranges were found from 5–1000 and 25–1000 ng·mL−1 for SPME-GC and SPME-LC, with detection limits of 5 ng·mL−1 for SPME-GC and 25 ng·mL−1 for SPME-LC. SPME can be used as a simple sample pretreatment method for the determination of lidocaine in urine by GC and LC.
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    Porous copolymer of the methacrylic ester of dihydroxydiphenylmethane diglycidyl ether and divinylbenzene as an HPLC packing (1998)
    Springer
    Chromatographia 47 (1998), S. 509-514 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Porous copolymers with hydroxyl groups ; Chemical modification of phases ; Selectivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Dimethyldichlorosilane has been used to deactivate the hydroxyl groups present in the skeleton of the porous polymer formed from the methacrylic ester ofp, p′-dihydroxydiphenylmethane diglycidyl ether and divinylbenzene. The influence of chemical modification of the copolymer on its chromatographic behavior has been studied. The retention indices of five homologous series and test compounds were calculated to determine the selectivity of the packings.
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    Analysis of anka pigments by liquid chromatography with diode array detection and tandem mass spectrometry (1998)
    Springer
    Chromatographia 47 (1998), S. 529-536 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Thin layer chromatography ; Mass spectrometry detection ; Anka pigments
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Anka is withMonascus sp. fermented rice, which shows a purplish red color. On rice grainsMonascus purpureus DSM 1379 synthesized four anka pigments. Through extraction of anka with n-hexane and methanol in succession and through repeated crystallizations from absolute ethanol anka pigments were crystallized into two fractions: organge anka pigments (rubropunctatin and monascorubrin) and yellow anka pigments (monascin and ankaflavin). The treatment of two organge anka pigments with aqueous ammonia solution gave red nitrogen analogues (rubropunctatamine and monascorubramine). The above six pigments were separated into each pigment by two dimensional thin layer chromatography (TLC) or high performance liquid chromatography (HPLC). HPLC-atmospheric pressure chemical ionization-tandem mass spectrometry (HPLC-APCI-MS-MS) and direct probe mass spectrometry (MS) were used to identify these pigments. HPLC-diode array detector (HPLC-DAD) was used to determine UV-VIS spectra of pigments. Pigments were analyzed with HPLC under the following conditions: C18 column, acetonitrile/water (80∶20, v/v), 0.5 mL min−1, 233 nm.
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    Determination of nalbuphine hydrochloride, methylparaben, and propylparaben in nalbuphine hydrochloride injection by high performance liquid chromatography (1998)
    Springer
    Chromatographia 47 (1998), S. 515-522 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; 4,5-Epoxymorphinan ; Nalbuphine hydrochloride injection ; Stability assays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A stability-indicating liquid chromatographic method has been developed for the determination of nalbuphine hydrochloride, methylparaben, and propylparaben in nalbuphine hydrochloride injection. Reversed-phase chromatography was carried out using a mobile phase containing 0.05 % trifuoroacetic acid, acetonitrile, and tetrahydrofuran. Quantitation was achieved with UV detection at 280 nm. Validation data for linearity, accuracy, precision, specificity, and robustness are presented. The chromatographic system resolves nalbuphine from synthetic impurities and degradation products.
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    Determination of the five major opium alkaloids by reversed-phase high-performance liquid chromatography on a base-deactivated stationary phase (1998)
    Springer
    Chromatographia 47 (1998), S. 21-24 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Opium alkaloids ; Papaver somniferum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A reversed phase HPLC method for the separation of the five major alkaloids fromPapaver somniferum L., morphine, codeine, thebaine, papaverine and noscapine, has been developed and validated. By use of a basedeactivated silica-based stationary phase excellent peak shape was achieved for each substance. The five alkaloids were quantified by internal standardization within 20 min and with good precision. The method is applicable to opium and to poppy straw.
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    Liquid chromatographic analysis of non-volatile strawberry compounds (1998)
    Springer
    Chromatographia 47 (1998), S. 197-202 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Non-volatile strawberry compounds ; Multivariate analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A procedure is presented for simultaneous extraction of organic acids, vitamin C and sugars from strawberries and analysis by reversed-phase (RP) HPLC and cationexchange (calcium form) chromatography. Recoveries from strawberries spiked at different levels ranged from 96 to 103 % for carbohydrates, 92 to 112 % for organic acids, and 84 % for vitamin C; the repeatability of the method evaluated as the relative standard deviation in the optimum range was 〈5 % for sugars and 7.5 % for organic acids and vitamin C. Multivariate analysis techniques, such as Bayes and SIMCA analyses, have enabled correct classification of the strawberries tested but we were unable to establish adequate models for typifying them according to their geographic origin.
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    On-line extraction and determination of carbofuran in raw milk by direct HPLC injection on an ISRP column (1998)
    Springer
    Chromatographia 47 (1998), S. 81-83 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Carbofuran pesticides ; On-line analysis of milk
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A method has been developed for extraction and determination of carbofuran in milk. The method involved direct injection of raw milk on to a human serum albumin dimethyloctyl-silica gel (HSA-C8) column and the use of 80:20 (v/v) 0.01 M phosphate buffer pH 5.5-acetonitrile as mobile phase. UV spectrophotometric detection was performed at 220 nm. Identification was based on retention time. Quantification was performed by automatic peak-area determination and was calibrated by use of an external standard.
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    The application of high performance liquid chromatography, coupled to nuclear magnetic resonance spectroscopy and mass spectrometry (HPLC-NMR-MS), to the characterisation of ibuprofen metabolites from human urine (1998)
    Springer
    Chromatographia 47 (1998), S. 264-270 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; NMR and MS detection ; Ibuprofen metabolites ; Urine extracts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The use of HPLC-NMR-MS for the detection and identification of the metabolites of ibuprofen present in a solid phase extract of human urine is described. Gradient reversed-phase HPLC was used to separate the components present in the extract, which were then characterised by a combination of stopped-flow1H NMR and on line electrospray-MS. This approach led to the rapid identification of the known phase 1 human metabolites of ibuprofen, including hydroxy- and carboxy- metabolites, together with their respective glucuronide conjugates. In addition a probable artefact resulting from the dehydration of one of the side chainhydroxylated glucuronides was also identified.
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    Use of short columns and high flow rates for rapid gradient reversed-phase chromatography (1998)
    Springer
    Chromatographia 47 (1998), S. 291-298 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Capillary electrochromatography ; Rapid analysis ; Short columns ; Rapid gradients
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Rapid analyses were performed using reversed-phase liquid chromatography with short (20–100 mm) columns swept by fast yet shallow gradients, and the results compared with those obtained with 150 mm columns and slow gradients. The resolution losses incurred with shorter columns were minimised by employing elevated flow rates, to ensure that comparable mean retention factors were experienced by individual analytes during gradients run on different columns. This conserves gradient steepness. High quality performance was obtained with turn-around times of 5–10 minutes. An overall 5-fold enhancement in the rate of information generation was obtained. The relevance of instrumental parameters and of column and packing dimensions, upon the potential for improved performance is discussed. Some implications for the rapidly developing technique of capillary electrochromatography are briefly indicated.
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    Separation of lansoprazole enantiomers in human serum by HPLC (1998)
    Springer
    Chromatographia 47 (1998), S. 171-175 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Lansoprazole ; Enantiomers ; Human serum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A new and simple HPLC method is described for the separation and quantitative determination of the (+)-and (−)-enantiomers of lansoprazole. The analytes were extracted from serum as previously described for whole lansoprazole [K. Borner, Chromatographia 45, 450–452 (1997)]. The enantiomers were separated by chromatography on a CHIRAL-AGPR column which contained covalently bound acid α1-glycoprotein as chiral selector. In the pure drug the (−)/(+) ratio was 0.99:1.01. In serum of twelve human volunteers the concentration of the (−)-enantiomer was 3 to 5 times higher than that of the (+)-enantiomer. Both enantiomers differ remarkably in their pharmacokinetics.
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    Determination of eleven priority EPA phenolics at ng L−1 levels by on-line solid-phase extraction and liquid chromatography with UV and electrochemical detection (1998)
    Springer
    Chromatographia 47 (1998), S. 176-182 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Electrochemical detection ; Phenolics in water ; On-line preconcentration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The eleven priority, EPA phenolic pollutants were determined by liquid chromatography followed by two detectors in series; UV and electrochemical. Three different adsorbents, Envi-Carb (a carbon black) and two functionalized polymeric resins, Bond Elut PPL and another synthesized in our laboratory with an ocarboxybenzoyl moiety, were compared for solid-phase extraction (SPE) to detect lower concentrations of the eleven phenolics in natural waters. Higher recoveries were obtained using the functionalized polymeric adsorbents compared with Envi-Carb. When real samples were analysed, the synthetic adsorbent gave lower interference than Bond Elut PPL and phenol was determined at low levels with no humic and fulvic acid inter-ference when Na2SO3 was added. The linearity range for most compounds in tap water was 0.05–20 μg L−1 and the limits of detection were 〈35 ng L−1. Repeatability and reproducibility between days for real samples spiked at 0.1 μg L−1, expressed as relative standard deviation, were 〈8% and 10%, respectively.
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    The use of mobile phase pH and column temperature to reverse the retention order of enantiomers on chiral-AGP® (1998)
    Springer
    Chromatographia 47 (1998), S. 189-196 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Experimental design ; Mosapride ; Reversal of retention order ; Effect of pH and column temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Enantiomeric separation of mosapride and a structurally related compound was performed using chiral chromatography and experimental design. Unique effects of mobile phase pH and column temperature made it possible to control the elution order of the enantiomers when using Chiral-AGP as the solid phase. At a low mobile phase pH (〈6) the (R)-enantiomer of mosapride elutes before the (S)-form whereas the (S)-enantiomer elutes first at a high mobile phase pH (〉6). By using a mobile phase pH around 6, the column temperature could also be used to control the elution order of the enantiomers of mosapride. Similar effects of mobile phase pH and column temperature were obtained for the enantiomers of a structurally related compound, a metabolite (M1). Isocratic chromatographic systems made it possible to determine enantiomeric impurities less than 0.1% in the respective enantiomer of mosapride. The enantiomers of mosapride as well as the enantiomers of M1 could easily be separated simultaneously using Chiral-AGP and a simple gradient elution.
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    HPLC determination of colistin and aminoglycoside antibiotics in feeds by post-column derivatization and fluorescence detection (1998)
    Springer
    Chromatographia 48 (1998), S. 32-36 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Post-column derivatization ; Feeds ; Aminoglycoside antibiotics ; Colistin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Reversed-phase, HPLC methods employing post-column derivatization and fluorescence detection were developed for the determination of the peptide colistin and four aminoglycoside antibiotics in feeds. Extraction of the analytes was by sonication and shaking with dilute hydrochloric acid. Post-column derivatization was performed using orthophtaldialdehyde-2-mercaptoethanol chemistry. Assay of colistin was by using an acetonitrile-aqueous sodium sulphate-triethylammonium phosphate (pH 2.8) eluent. Aminoglycoside antibiotics:amikacin, kanamycin, gentamycin and neomycin were analyzed using a tetrahydrofuran-aqueous sodium sulphate-sodium pentanesulphonate-acetic acid mobile phase. The method was also applied to some pharmaceutical preparations. Preliminary results showed that the method can be adapted for the assay of the above antibiotics in meat and animal serum for residue and pharmacokinetic studies.
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    High-Performance liquid chromatographic separation of enantiomers of unusual amino acids possessing cycloalkane or cycloalkene skeletons on a chiral crown ether containing stationary phase (1998)
    Springer
    Chromatographia 48 (1998), S. 20-26 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Crownpak CR(+) Column ; Cyclic β-Amino Acids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Direct reversed-phase high-performance liquid chromatographic methods were developed for the separation and identification of the enantiomers of mono- and bicyclic racemic β-amino acids:cis- andtrans-2-aminocyclopentane-1-carboxylic acids,cis- andtrans-2-aminocyclohexane-1-carboxylic acids,cis- andtrans-2-amino-4-cyclohexene-1-carboxylic acids,diendo- anddiexo-3-aminobicyclo[2.2.1]heptane-2-carboxylic acids anddiendo- anddiexo-3-amino-5-bicyclo[2.2.1]heptene-2-carboxylic acids. Enantioseparation was carried out by the application of a chiral stationary phase, Crownpak CR(+). The conditions of separation were optimized by changing the temperature, the flow rate and the pH of the mobile phase.
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    Enantiomeric separation of unusual secondary aromatic amino acids (1998)
    Springer
    Chromatographia 48 (1998), S. 53-58 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Gas chromatography ; Enantiomeric separation ; Chiral derivatization ; Unusual secondary aromatic amino acids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary High-performance liquid chromatographic and gas chromatographic methods were developed for the separation of unusual secondary aromatic amino acids. Amino acids containing 1,2,3,4-tetrahydroisoquinoline, 1,2,3,4-tetrahydronorharmane-1-carboxylic acid and 1,2,3,4-tetrahydro-3-carboxy-2-carboline moieties were synthetized in racemic or chiral forms. The high-performance liquid chromatography was carried out either on a teicoplanin-containing chiral stationary phase or on an achiral C18 column. In the latter case the diastereomers of the amino acids formed by precolumn derivatization with the chiral reagents 2,3,4,6-tetra-O-acetyl-β-D-glucopyranosyl isothiocyanate or 1-fluoro-2,4-dinitrophenyl-5-L-alanine amide were separated. The gas chromatographic analyses were based on separation on a Chirasil-L-Val column.
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    Determination of two metabolites of albendazole, albendazole-sulfoxide and albendazole-sulfone in cow's milk using an HPLC method —A systematic approach to optimise extraction conditions (1998)
    Springer
    Chromatographia 48 (1998), S. 777-784 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Solid phase extraction ; Sample treatment optimisation ; Taguchi method ; Albendazole metabolites ; Milk samples
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Reversed phase HPLC methods for the determination of two metabolites of albendazole in cow's milk are described. Albendazole is an anthelmintic agent used both in veterinary and human practice. Its main metabolites are albendazole-sulfoxide and albendazole-sulfone. The separation of the two metabolites was performed on a μ-Bondapak C-18 column using an acetonitrile/methanol/phosphate buffer as mobile phase, with detection at 290 nm. For the sample preparation of the milk samples we used solid phase extraction. A new sample treatment optimisation procedure is also presented for the sample preparation method. Since sample preparation is a critical step in the analysis of residues in biological samples, the second part of our publication describes an optimisation using Taguchi's methodology that increased recovery, accuracy and reliability. After optimisation of the sample preparation, the limit of detection was 10 ng mL−1 milk and the recovery was 70–80% in the concentration range of 30–1000 ng mL−1 milk for both metabolities.
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    Development and validation of stability indicating high-performance liquid chromatographic assays for ketotifen in aqueous and silicon oil formulations (1998)
    Springer
    Chromatographia 48 (1998), S. 797-802 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ketotifen analysis ; Stability indicating analysis ; Aqueous and oil-based formulations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A simple and specific high-performance liquid chromatographic (HPLC) method for the analysis of ketotifen in aqueous solutions and silicon oil suspensions is described. The HPLC system is based on a reversed phase μBondapak C18 (30×0.39 cm) column with a mobile phase of phosphate buffer (0.001 M, pH 7.4):methanol: acetonitrile: trimethylamine (29.8:45:25:0.2, by volume) at a flow-rate of 1 mL min−1. The eluent was monitored by UV absorption at 299 nm. Silicon oil-based samples were extracted with HCl (0.05 M) using imipramine as internal standard. The recovery of ketotifen and imipramine was greater than 80%. The calibration curves for both assays were linear over the ranges examined, yielding correlation coefficients greater than 0.997. The assay was shown to be stability indicating by subjecting solutions of ketotifen in phosphate buffer to heat, oxidative stress and irradiation with ultraviolet light (254 and 369 nm)for up to 8 h. The methodology was also shown to be applicable for the analysis of ketotifen in simple aqueous based formulations, in suspension in silicon oil and for the analysis of samples derived fromin vitro skin transfer experiments.
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    Determination of ketorolac enantiomers in plasma using enantioselective liquid chromatography. Application to pharmacokinetic studies (1998)
    Springer
    Chromatographia 48 (1998), S. 203-208 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ketorolac in plasma ; Enantiomer separation ; Pharmacokinetic studies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A direct HPLC method for quantification of the (R) and (S) enantiomers of ketorolac in human plasma for pharmacokinetics studies has been developed. Naproxen sodium [S(+) enantiomer] was used as an internal standard. Plasma samples (1 mL) were vortexed for 30 sec with methyltert-butyl ether, followed by centrifugation at 2000 g for 8 min. The aqueous phase was acidified (pH 1) by adding 1 mL of 2N HCl and back-extracted with 5 mL methyltert-butyl ether. The organic phase was evaporated, and the residue was dissolved in 200 μL of mobile phase. 25 μL were chromatographed on a α1-acid glycoprotein column (Chiral-AGP, 100×4 mm I.D.), using a mobile phase with 8.5% propan-2-ol in phosphate buffer (0.09M NaH2PO4.H2O, 0.01M Na2HPO4, 0.002M Dimethyloctylamine; pH 5.5). Calibration range was 20–20000 ng mL−1 for (R)- and (S)-ketorolac. The LOQ was 5 ng mL−1 for both enantiomers. The sensitivity could be extended to 1 ng mL−1 with the same precison by increasing the injection volume to 100 μL. The method is reproducible, accurate, and stereospecific. The inter-assay and intra-assay CVs were 〈11.40% and 〈9.30% for (R)- and (S)-ketorolac respectively. Under the conditions employed, no racemization was observed.
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    Optimisation of mobile phase pH in liquid chromatography. Application to fluorimetric detection of series of quinolones (1998)
    Springer
    Chromatographia 48 (1998), S. 251-257 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Mobile phase optimisation ; Fluorimetric detection ; Quinolones ; Dissociation constants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The dissociation constants of several quinolones in a 7% acetonitrile-water mixture are determined. A model describing the effect of pH on the retention of quinolones by an octadecylsilica stationary phase with a 7% acetonitrile-water mobile phase is proposed. The model uses pH values in the mobile phase instead of pH values in water and takes into account the effect of activity coefficients. Fluorescence of quinolones in the mobile phase is studied, and a chromatographic separation with fluorimetric detection is established. Detection limits for the proposed method range from 3 to 12 μg·L−1.
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    Effects of amine additives on the resolution of antipsychotic and antidepressant drugs on a cyanoalkyl HPLC column (1998)
    Springer
    Chromatographia 48 (1998), S. 770-776 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Basic drug compounds ; Amino additives ; Cyanoalkyl columns
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The separation of basic antidepressant and antipsychotic drugs on a cyanoalkyl-bonded silica column has been studied to determine the effects on peak retention, symmetry, efficiency, and resolution of six different amine mobile-phase additives. The amines—ammonia,n-butylamine, triethylamine,N,N-diisopropylethylamine,N,N-dimethylbutylamine andN,N-dimethyloctylamine—were, except forN,N-diisopropylethylamine, chosen because of their widespread use for improvement of peak symmetry in chromatographic methods;N,N-diisopropylethylamine was included as an example of a sterically hindered amine to see if the stereochemistry around the nitrogen atom is an important consideration in the selection of an additive. This study shows that a gain in symmetry and efficiency is accompanied by loss of resolution. The results obtained also indicate that one type of amine additive should be used when symmetry and efficiency are most important and another when resolution is paramount.
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    Extraction and liquid-chromatographic determination of amphotericin B in oil-water lecithin-based microemulsions (1998)
    Springer
    Chromatographia 48 (1998), S. 803-806 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Amphotericin B ; Oil-water lecithin-based microemulsions ; Extraction of drug from microemulsion ; Reversed-phase HPLC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A method employing extraction then reproducible reversed-phase high-performance liquid chromatography (RPHPLC) with monitoring of the drug by absorbance at 405 nm has been developed and validated for the determination of amphotericin B in oil-water lecithin-based microemulsions. The precision and accuracy of the method are excellent (SD 2.4% and 4.2%, respectively). The established linearity range was 10–60 μg mL−1 (r 2=0.9967). The recovery of amphotericin B from spiked placebo was 〉90% over the linear range. The extraction procedure was simple and the HPLC conditions were able to separate the drug from its degradation products and excipients. The method has been used successfully for determining the amphotericin B content of microemulsions and for evaluating the chemical stability of amphotericin B-loaded microemulsions.
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    Studies on shape selectivity of RP C18-columns (1998)
    Springer
    Chromatographia 48 (1998), S. 183-189 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Polymeric phases ; Shape selectivity ; PAH selectivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Stationary phases with octadecyl groups have been prepared with different carbon content without and in the presence of water and characterized for their selectivity for the shape of various polyaromatic hydrocarbons. It is shown that both a high hydrocarbon content and a good accessibility of the bonded groups within the pores is required to achieve shape recognition for PAH. High carbon content alone is not sufficient. The two tests for shape selectivity proposed by Sander and Wise as well as by Tanaka are compared. In most cases the results are similar: A low selectivity with the Sander and Wise test (α TBN/BaP〈1) corresponds to a high value with the Tanaka test (α TRI/o-TER〉3). However, not in all cases the tests give corresponding answers. Further studies on molecular recognition are required.
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    Chiral recognition by molecularly imprinted polymers in aqueous media (1998)
    Springer
    Chromatographia 48 (1998), S. 197-202 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Molecular imprinting ; Molecular recognition ; Chiral recognition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Molecularly imprinted polymers were prepared using 2-vinylpyridine and/or methacrylic acid as functional monomers in a self-assembly imprinting protocol. The resulting polymers were analyzed in aqueous media, and the effects from the pH of the mobile phase and the degree of added organic solvent were investigated. The results are indicative of the importance of ionic bonds in conjunction with hydrophobic interactions in the formation of the complexes between the analyte and the polymers.
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    Dye-coated stationary-phases: A retention model for anions in ion-interaction chromatography (1998)
    Springer
    Chromatographia 48 (1998), S. 190-196 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ion-interaction chromatography ; Dye-coated reversed phase ; Retention model ; Experimental design
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The separation of inorganic anions (NO3 −, NO2 −, Cl−, Br−, I−, SO4 2−, S2O3 2−) by ion-interaction chromatography mediated with a specific dye has been investigated. Chromatography was performed on a LiChrospher RP-18 colum dynamically coated with crystal violet, using acetonitrile-water buffered with phthalate as the mobile phase. The presence of the dye in the eluent enabled indirect spectrophotometric detection of the analytes, which have no significant UV absorption. Retention data were collected for the different anions by varying the composition of the mobile phase according to a full factorial experimental design. A theoretical model for the retention of singly- and doubly-charged analytes, on the basis of the two main processes of ion-exchange and ion-pair formation, has been proposed and validated with the experimental data.
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    URL: http://dx.doi.org/10.1007/BF02467670
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    Wheat β-amylase behaviour regarding salt promoted adsorption processes (1998)
    Springer
    Chromatographia 48 (1998), S. 209-214 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Covalent chromatography ; Thiophilic and hydrophobic ligands ; Wheat β-amylase ; Salt promoted adsorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The behaviour of wheat β-amylase from crude extracts in chromatography on agarose gels substituted with different ligand types was investigated. The enzyme displayed high salt promoted adsorption onto thiophilic gels provided with sulfone-thioether and 2-thiopyridine ligands. Quantitative recovery of the enzyme was easily accomplished by elution with buffer in the absence of Na2SO4. The 3-(2-pyridylthio)-2-hydroxypropylagarose (PyS-gel) also allowed elimination of pigments present in the wheat extract. These pigments showed no adsorption onto the gel, thus regeneration is easily achieved, allowing its re-use. The enzyme also displayed strong salt-dependent adsorption onto adsorbents provided with pyridyldisulfide moieties, but in this case enzyme binding was due to its thiol content since elution was achieved mainly through reduction with DTT. When the enzyme was chromatographed on a series of hydrophobic alkyl ligands in the presence of 0.5 M sodium sulphate, it was partially adsorbed on pentylagarose and quantitatively adsorbed on hexyl-agarose, elution being easily performed by sodium sulphate-free buffer. This behaviour was markedly different from that towards phenyl-Sepharose, to which the enzyme was strongly adsorbed and which required much more drastic elution conditions.
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    URL: http://dx.doi.org/10.1007/BF02467673
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  • 87
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    Characterization of peak purity by fast multiscan circular dichroism detection (1998)
    Springer
    Chromatographia 48 (1998), S. 584-588 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Circular dichroism detection ; Multiscan detection ; Peak purity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A method has been developed to detect inhomogeneity of apparently homogeneous peaks of very similar analytes. The method utilizes the rapid scan feature of state-of-the-art spectrometers/detectors that allow the recording of up to 30 spectra in a single chromatographic peak. Sensitivity and selectivity are enhanced by chiroptical/optical detection. Thus, identification of “front” and “rear” components of the peak can be carried out. The method is exemplified by mixtures of codeine, hydrocodone and oxycodone as analytes.
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    URL: http://dx.doi.org/10.1007/BF02466654
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  • 88
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    Determination of myristicin in rat serum samples using microbore high performance liquid chromatography with column-switching (1998)
    Springer
    Chromatographia 48 (1998), S. 365-368 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Microbore columns ; Column-switching ; Myristicin ; Serum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A microbore high-performance liquid chromatographic method with column-switching was developed for the analysis of myristicin from rat serum without prepurification. Deproteinization, fractionation, concentration and separation of analyte were carried out by appropriate switching of columns and using solvent mixtures. The method showed excellent precision, accuracy and speed with a detection limit of 10 ng mL−1 from 25 μL of serum. The total analysis time per sample was 25 min and the coefficients of variation for intra- and inter-assay were less than 1.8%.
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    URL: http://dx.doi.org/10.1007/BF02467705
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    Determination of cisplatin, transplatin and amminetri-chloroplatinate by high performance liquid chromatography in one run using 4-methyl-2-thiouracil as derivatizing agent (1999)
    Springer
    Chromatographia 49 (1999), S. 562-566 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Cis-diamminedichloroplatinum (II) ; Transdiamminedichloroplatinum (II) ; Amminetri-chloroplatinate ; 4-Methyl-2-thiouracil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary We have developed a simple, rapid, selective and sensitive method for detecting the antitumour agent cis-diamminedichloroplatinum (II) (cisplatin) (CDDP) and its toxic impurities trans-diamminedichloroplatinum (II) (transplatin) (TDDP) amminetri-chloroplatinat (ATCP) anion using HPLC in one run. By using 4-methyl-2-thiouracil (MTU) as a derivatizing agent, new compounds have been formed from the Pt compounds and separated on a μ-Bondapak C18 column with isocratic elution and detection at 315 nm. Reactant concentration, methanol content, pH and the reaction time on yield of derivatives were investigated and the optimum conditions for the detection response were defined. The derivatives of each of the three platinum compounds formed in an acetate buffer solution containing 40% (v/v) methanol and 0.9% KCl solution at pH 3.7 and ambient temperature were only stable for one hour.
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    URL: http://dx.doi.org/10.1007/BF02467760
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  • 90
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    Unexpected behavior of digoxin at elevated temperatures in reversed-phase liquid chromatography (1999)
    Springer
    Chromatographia 49 (1999), S. 306-308 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Digoxin and digoxigenin ; Temperature effects ; Pore size effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Increased retention of digoxin has been observed at elevated temperatures on both 10 nm and 30 nm porediamter, RP-18 packing. This result is the opposite effect compared with the decreased retention under the same conditions with digoxin aglycon-digoxigenin. Rotation around the C−C σ-bonds in the digoxin molecule is presumed; the rod-like molecules of the newlyobtained digoxin penetrate stationary phase pores more easily thus increasing retention.
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    URL: http://dx.doi.org/10.1007/BF02467561
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    Liquid chromatography of jasmonic acid amine conjugates (1999)
    Springer
    Chromatographia 49 (1999), S. 42-46 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chiral resolution ; Jasmonic acid ; Plant growth regulators ; Amine conjugates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Racemic jasmonic acid (3R,7R/3S,7S)-(±)-JA) was chemically conjugated with different biogenic amines originating from aliphatic and aromatic α-amino acids by decarboxylation. The resulting isomeric compounds were subjected to reversed-phase high-performance liquid chromatography (HPLC) and to HPLC on the chiral stationary phases Chiralpak AS and Nucleodex β-PM. Under reversed-phase conditions, all the homologous amine derivatives tested could be separated from each other except the JA-conjugates containing 2-phenyl-ethylamine and 3-methylbutylamine. On both chiral supports the (3R,7R)-(−)-JA conjugates eluted earlier than those of the enantiomeric counterpart (3S,7S)-(+)-JA. On Chiralpak AS all the isomers studied could be separated to baseline with a mobile phase containingn-hexane and 2-propanol. The calculated resolution factors were between 1.80 and 4.17. The pairs of isomers were also chromatographed on the cyclodextrin stationary phase Nucleodex β-PM with methanol-triethylammonium acetate buffer as mobile phase. Under these conditions resolution factors were between 0.74 and 1.29. The individual isomers were chiroptically characterized by measurement of their circular dichroism.
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    URL: http://dx.doi.org/10.1007/BF02467185
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    Determination of ethinylestradiol and gestodene in oral contraceptives by micellar electrokinetic chromatography (1999)
    Springer
    Chromatographia 49 (1999), S. 65-70 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Micellar electrokinetic chromatography (MEKC) ; Oral contraceptives ; Ethinylestradiol ; Gestodene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A micellar electrokinetic chromatographic method is presented which permits quantification of ethinylestradiol and gestodene in pharmaceutical products. Separation was carried out at 25°C and 25 KV, using a 20 mM borate buffer (pH 9.2), 15 mM sodium dodecylsulfate in 30% acetonitrile-water (v/v). Under these conditions analyses were carried out in 7 min. Four different oral contraceptives were analysed and the results compared favourably with those of a reference liquid chromatographic method.
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    URL: http://dx.doi.org/10.1007/BF02467189
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    Determination of yttrium and lanthanum in zirconium dioxide by HPLC, X-ray fluorescence and neutron activation analyses (1999)
    Springer
    Chromatographia 49 (1999), S. 91-94 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Zirconium oxide ceramics ; X-ray fluorescence ; Neutron activation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Lanthania-and yttria-stabilized zirconium oxide ceramics have been examined using High Performance Liquid Chromatography (HPLC), thermal neutron activation (NA) and X-ray Fluorescence (XRF) analyses and thus determine the stabilizer content. Ceramic powders with the composition ZrO2:x mol % La2O3 (x=5, 10, 15, 20 and 33) and ZrO2:x mol % Y2O3 (x=10, 15, 20 and 25) were prepared by the citrate and the co-precipitation techniques, respectively. The lanthanum content was determined by HPLC (x=5.09, 9.78, 14.98, 19.81 and 25.94) and NA (x=5.15, 10.32, 17.25, 21.08 and 27.97) analyses, the yttrium content by HPLC (x=8.5, 13.5, 17.9 and 22.1) and XRF (x=9.9, 15.8, 20.1 and 24.9) analyses. An experimental sequence, based on continuous dilution of ceramic powder solutions, is proposed for preparing samples for HPLC measurements. A swimming pool nuclear reactor is used for NA analysis. The quantitative determinations of yttrium and lanthanum doping levels obtained using those techniques are described.
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    URL: http://dx.doi.org/10.1007/BF02467194
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    Stereochemical resolution of racemates, in HPLC, using a chiral stationary phase based upon immobilized α-chymotrypsin. I. Structural chiral separations (1999)
    Springer
    Chromatographia 49 (1999), S. 595-605 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; α-Chymotrypsin immobilized on silica ; In situ immobilization process ; Structural chiral separations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary α-Chymotrypsin was immobilized on an epoxide derivatized silica gel by anin situ immobilization process. Several racemates were resolved by a structural recognition mechanism. The immobilization process and the stability of this α-chymotrypsin stationary phase have been studied. The mobile phase parameters including the ionic strength, pH and the effects of organic modifiers have been also investigated. The retention, efficiency and stereoselectivity of the solutes appear to be related to their molecular structure, hydrophobicity and electrostatic interactions. These relationships determine the recognition mechanism and the position of each enantiomer in the active site.
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    URL: http://dx.doi.org/10.1007/BF02466900
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    High performance liquid chromatography coupled to nuclear magnetic resonance spectroscopy and mass spectrometry applied to plant products: Identification of ecdysteroids fromSilene otites (1999)
    Springer
    Chromatographia 49 (1999), S. 374-378 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; NMR spectroscopy and mass spectrometry ; Plant products ; Silene otites
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary HPLC coupled in parallel to nuclear magnetic resonance (NMR) and mass spectrometry (MS) has been used to obtain1H NMR and mass spectra of a number of ecdysteroids present in an extract of the plantSilene otites. Reversed phase gradient chromatography was performed using a D20-acetonitrile-based solvent system. NMR and mass spectra were obtained for integristerone A, 20-hydroxyecdysone, 2-deoxy-20-hydroxyecdysone and 2-deoxyecdysone to provide structural confirmation using continuous and stopped flow HPLC-NMR. The combined HPLC-NMR-MS system described here provided a more comprehensive analysis of the ecdysteroids present in the extract than HPLC-NMR alone.
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    URL: http://dx.doi.org/10.1007/BF02467609
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    Separation of human serum albumin components by RP-HPLC and CZE and their characterization by ESI-MS (1999)
    Springer
    Chromatographia 49 (1999), S. S21 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Capillary zone electrophoresis ; Electrospray ionization-mass spectrometry ; Human serum albumin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Human serum albumin (HSA) is one of the most abundant human proteins and has been shown to be heterogeneous. A RP-HPLC method has been developed to separate HSA components in commercially available preparations. Separations were carried out on Aquapore RP-300, C8 columns using gradient elution with a combination of acetonitrile/water mobile phases containing 0.05% trifluoroacetic acid as ion-pairing agent. Optimum resolution was attained on narrow-bore columns using a stepwise, linear gradient that incorporated a shallow intermediate step of 0.20%/min in Mobile Phase B. Under similar elution conditions, separations carried out on standard-size columns showed the expected decrease in resolution due to increased peak widths. A comparative analysis of three commercial products highlighted qualitative and quantitative differences. Capillary zone electrophoresis was used for the analysis of collected RP-HPLC fractions. Results indicated that while the HPLC separation was incomplete, one of the major HPLC peaks was primarily composed of one of the three main components typically separated by CZE. ESI-MS was used to characterize the two major RP-HPLC fractions and also showed that the HPLC separation was incomplete. The MaxEnt transform of the HPLC peaks was consistent with components all being HSA and closely related derivatives.
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    URL: http://dx.doi.org/10.1007/BF02468972
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    Chiral chromatography of amino- and hydroxy-acids on surface modified porous graphite (1995)
    Springer
    Chromatographia 40 (1995), S. 9-14 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Porous graphite ; Chiral stationary phase ; Copper complexation chromatography ; Amino acids ; Hydroxy acids ; Adsorbed stationary phases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A new type of chiral stationary phase has been prepared by coating porous graphite with a near-monolayer of an adsorbed enantiomeric modifier which then acts as an adsorbed stationary phase. The most effective modifiers are L- or D-isomers of N-(2-naphthalene-sulphonyl)-phenylalanine (NS-Phe). Conveniently 80% of monolayer coverages, corresponding to 1.2 μmol m−2, are achieved by adsorption of NS-Phe from methanolic solution. Enantiomeric separations by complexation with cupric ion show base-line resolution of α-amino and α-hydroxy acids with separation factors up to 2. Identical separations are achieved with chiral phases made from the L- and D-isomers of NS-Phe except that the elution orders of enantiomers are inverted. Reduced plate heights are around 5 and the adsorbed chiral phases are extremely stable, retention ratios being unchanged after passage of 7000 column volumes of eluent. A mechanism of retention is proposed, which fits the experimental observations.
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    URL: http://dx.doi.org/10.1007/BF02274600
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    Screening of water samples for polar organic micropollutants using on-column sample enrichment (1995)
    Springer
    Chromatographia 40 (1995), S. 631-637 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Trace analysis ; Pesticides in tap water ; Aromatic sulphonates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Methodology and instrumentation are described which allow chromatographic screening of water samples under substantially simplified conditions and at reduced cost. A single column is used to accomplish sample extraction, trace enrichment, and separation. The performance of such a system is demonstrated, and the results compared with conventionally used concepts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02315129
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    Determination of vitamin A in pharmaceutical preparations by high-performance liquid chromatography with diode-array detection (1995)
    Springer
    Chromatographia 40 (1995), S. 143-146 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Diode-array detection ; Retinol acetate ; Pharmaceutical preparations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A very simple high-performance liquid chromatographic method for determination of Vitamin A in pharmaceutical preparations without the need for saponification was developed. A reversed-phase (Nova-Pack C18, 4 μm) column was used with a mobile phase of acetonitrile-tetrahydrofuran-water (55∶37∶8) and a flowrate of 1.5 ml/min. Sample treatment only consisted of the extraction of retinol acetate content from capsules or tablets with methanol. Total extraction was achieved by shaking vigorously with the aid of magnetic stirring for three hours at room temperature. No change of solvent is necessary to introduce the sample in the chromatographic system. This method is suitable for routine quantification of Vitamin A.
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    URL: http://dx.doi.org/10.1007/BF02272162
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    Retention in liquid chromatography with multicomponent mobile phases: Relationship with binary systems (1995)
    Springer
    Chromatographia 40 (1995), S. 321-328 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Multicomponent mobile phases ; Retention prediction ; Binary and multicomponent phases, comparison
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Using the concept of an effective concentration a method is proposed for predicting retention in liquid chromatography with multicomponent mobile phases based on experiments with corresponding binary ones. The method is verified for normal and reversed-phase systems with ternary mobile phases and agrees closely with experimental data.
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    URL: http://dx.doi.org/10.1007/BF02290364
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