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  • Column liquid chromatography  (23)
  • Nederland
  • Superfluidity and superconductivity
  • verspreiding
  • Springer  (23)
  • 1
    Electronic Resource
    Electronic Resource
    Zone electrophoretic sample treatment coupled on-line with column liquid chromatography for the determination of basic and acidic compounds in biological samples (1992)
    Springer
    Chromatographia 34 (1992), S. 581-588 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Zone-electrophoretic sample treatment ; Basic and acidic compounds ; Biological samples
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A modified valve arrangement for zone-electrophoretic sample treatment (ZEST)-which is coupled on-line with column liquid chromatography — is used to pretreat biological (plasma) samples. Carry-over of plasma proteins depends on the pH of the electrophoresis buffer. The determination of propranolol, metoprolol, cromolyn and salicylic acid demonstrates that both basic and acidic analytes can be isolated from the plasma matrix with high selectivity. Analogous piperazines, with different protein binding properties, were used to study the influence of protein binding on the recovery. It is shown that high protein can cause a decreased recovery.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02269867
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  • 2
    Electronic Resource
    Electronic Resource
    A new valve for zone-electrophoretic sample treatment coupled on-line with high performance liquid chromatography (1990)
    Springer
    Chromatographia 29 (1990), S. 217-222 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Sample treatment ; Zone electrophoresis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The design of a new valve arrangement for zone-electrophoretic sample treatment (ZEST) coupled online with high performance liquid chromatography is described. Characteristics of this valve, such as the internal heat development as a function of the current, have been investigated. By using quinidine and desipramine as model compounds it is shown that charged compounds can be isolated from biological samples, in about 15 min, with high selectivity. The carry-over of proteins to the analytical column has been compared with the carry-over using a pre-column sample clean-up method. The detection limits of quinidine and hydroquinidine (50 ng/ml), using zone-electrophoretic sample treatment coupled with column liquid chromatography, are in the same range as with direct injections using pre-columns.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02317907
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  • 3
    Electronic Resource
    Electronic Resource
    Electrodialytic sample treatment coupled on-line with high-performance liquid chromatography (1990)
    Springer
    Chromatographia 30 (1990), S. 361-366 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Electrodialytic sample treatment ; On-line coupling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An electrodialytic sample treatment method coupled on-line with high-performance liquid chromatography (EDIST-HPLC) is discussed in this paper. The performance of EDIST as a function of the donor-phase (sample solution) flow rate, the voltage applied over the electrodialysis block, and the time of dialysis has been studied using the basic drug ephedrine as a model compound. Enrichment of the analyte by a factor of 10–20 was possible. The determination of human plasma spiked with ephedrine is briefly discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02328498
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  • 4
    Electronic Resource
    Electronic Resource
    Theoretical models for electrodialytic sample treatment in trace analysis by liquid chromatography (1994)
    Springer
    Chromatographia 39 (1994), S. 460-468 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Electrodialytic sample treatment ; Computer models ; Analyte enrichment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Basic considerations for analyte enrichment and recovery obtainable by electrodialysis as a sample treatment method are given. Equations are derived which describe the dependence of the concentration profiles of ionic compounds on the electric field strength in a set-up with stagnant donor and acceptor solutions. It is shown that analyte recovery increases when less ion-selective membranes are used in the electrodialysis cell. Computer models are used to estimate the analyte enrichment for a flowing donor (sample) and a stagnant acceptor phase. About 10-fold enrichment can be obtained in an electrodialytic sample treatment system within 20 min under maximum current conditions. A compromise has to be found between analyte recovery and the donor (sample) flow rate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02278763
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  • 5
    Electronic Resource
    Electronic Resource
    Optimization of enantiomeric separations with chiral bonded phases (1986)
    Springer
    Chromatographia 21 (1986), S. 205-213 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chiral phases ; Optimization of separation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The preparation and properties of chiral bonded phases with amino acid groups are described. These phases were used in non-polar eluents and in aqueous systems in the presence of Cu2+ ions in the ligand-exchange mode. The optimization of chiral resolution is demonstrated for both cases. With non-polar eluents similarity between bonded groups and solutes is required. The elution could be accelerated by non-protonic moderators. Ligand-exchange separation is influenced by the copper content of the eluent and the stationary phase, the organic moderator concentration, the pH and ionic strength of the buffer and by the temperature. Structural requirements of both the bonded groups and of the solutes for chiral separation are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02311888
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  • 6
    Electronic Resource
    Electronic Resource
    On-line trace enrichment — column liquid chromatography of polar pollutants in surface water using bifunctional membrane-based extraction-disk cartridges (1994)
    Springer
    Chromatographia 39 (1994), S. 239-245 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Membrane-extraction disks ; On-line trace enrichment ; Polar pollutants ; Surface water
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An on-line trace-enrichment system, using a bifunctional membrane extraction-disk cartridge, has been combined with a column liquid chromatography separation for the simultaneous determination of basic, neutral and acidic pollutants in surface water. The enrichment device consisted of a specially constructed holder containing both C-18 and cation-exchange disks. The holder can contain up to 25 disks of 0.5 mm thickness and 4.6 mm diameter. Before trace enrichment of 20 ml of surface water (pH 3.0), calcium ions were removed from the sample by means of an oxalic acid precipitation. Desorption of the cartridge was at elevated temperature using reversed-phase gradient elution; detection was performed with a diode-array UV absorbance detector. The detection limits for the test compounds in surface water are typically 0.5–2 μg/l; the calibration graphs are linear from the lower limit of determination up to 50 μg/l.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02274506
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  • 7
    Electronic Resource
    Electronic Resource
    Determination of D- and L-amino acids in biological samples by two-dimensional column liquid chromatography (1995)
    Springer
    Chromatographia 41 (1995), S. 6-14 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Two-dimensional separation ; D- and L-amino acids ; Enantioseperation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A two-dimensional, column liquid chromatographic system is used for the determination of the D- and L-enantiomers of amino acids in biological samples. Separation of the amino acids is first on ion-exchange column by gradient elution with a sodium citratesodium chloride buffer. Enantioseparation is by subsequent injection of 3 μl heart-cuts of the individual amino acids onto a second column with a chiral crown ether stationary phase. Finally, fluorescence detection is after post-column labelling of the amino acids using ano-phthalaldehyde-2-mercaptoethanol reagent solution. The high separation power and selectivity of the system allow processing of complex samples with hardly any additional treatment and the determination of small quantities of D-amino acids in the presence of excess L-form. Applicability of the system is illustrated by the determination of D- and L-aspartate, serine, glutamate and alanine in various complex biological samples, such as protein hydrolysates, urine and biotechnological and food samples. Data are given on detectability, repeatability and linearity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02274188
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  • 8
    Electronic Resource
    Electronic Resource
    Use of two-dimensional liquid chromatography in the analysis of additives in cellulose acetate polymer (1988)
    Springer
    Chromatographia 25 (1988), S. 791-796 
    Details
    ISSN: 1612-1112
    Keywords: Gel permeation ; Column liquid chromatography ; Column switching ; Additives in cellulose acetate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The capability of elution-elution multi-dimensional liquid chromatography was investigated. A “column scaling” approach was evaluated for the quantification of low-molecular-weight additives in cellulose acetate. A small-bore (1-mm i.d.) gel-permeation column was used to separate the higher-molecular-weight polymer from the lower-molecular-weight components. Once separated these additives were transferred to a C18 reversed-phase column via a switching valve. The reversed-phase system successfully separated and quantified individual additives. Analysis time for an ultraviolet inhibitor, Tinuvin®P, in cellulose acetate, including re-equilibration, was approximately 30 minutes. Both accuracy and precision were good. Precision over a three day period was about 1.5%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02262086
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  • 9
    Electronic Resource
    Electronic Resource
    On-line procedures for the phase-transfer-catalyzed dansylation of phenolic steroids — Application to biological samples (1988)
    Springer
    Chromatographia 26 (1988), S. 267-273 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Phase-transfer catalysis ; On-line derivatization ; Phenolic steroids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Commercially available equipment from two manufacturers served to set up an automated system for the precolumn phase-transfer-catalyzed dansylation of phenolic steroids, using ethynyl estradiol (EE) and estradiol (E) as model compounds. Using different mixing techniques, the on-line determination of EE and E in 200μl untreated urine samples was achieved at a rate of 3–8 analyses per hour. Detection limits were calculated to be 3–5 ng/ml. Calibration curves in urine were linear over two orders of magnitude with r=0.999 (n=5) for EE and r=0.999 (n=6) for E. The repeatability of the determination of EE in urine (1μg/ml) was 3.9% (RSD; n=20) and of E (1.5μl/ml) 3.8% (RDS; n=10). The use of plasma instead of urine in the on-line procedures was not possible due to rapid formation of emulsions, but E and EE were determined in 100μl plasma samples using a mild off-line mixing procedure in 10min. Detection limits were calculated to be ca 10ng/ml. A reaction detector, based on a solvent-segmented system, was developed for the on-line post-column dansylation of phenols and was coupled with a reversed-phase LC system. The highly selective system showed excellent linearity over at least two orders of magnitude with r=0.9999 (n=6) for both phenol and 2,5-dimethylphenol. The reproducibility was good with RSD values of around 2%. Detection limits for loop injections from standard solutions were calculated to be between 4 and 11ng.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02268165
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  • 10
    Electronic Resource
    Electronic Resource
    Measurement of elastin hydrolysis by reverse-phase HPLC with on-line post-colum derivatization (1989)
    Springer
    Chromatographia 27 (1989), S. 225-227 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Reverse-phase chromatography ; Elastin Hydrolysis measurement ; On-line post-column derivatization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Excessive breakdown of elastin, a structural protein, may be related to aortic disease and emphysema. Since L-valyl-L-proline occurs in high concentrations in elastin, a rapid and sensitive method using HPLC with post-column on-line derivatization was used to measure the dipeptide from swine aortic tissue, and the amount of elastin present was determined. Elastin was extracted by alkaline hydrolysis. After neutralization and filtration, the sample was injected onto a ODS-2 gel column, and the dipeptide was eluted by a linear gradient of 0 to 10% of 1-propanol in 50 mM heptafluorobutyrate, pH 3, at a flow rate of 1 ml/min. The eluent was reacted with fluorescamine at pH 8.6, and fluorescence was detected at an excitation wavelength of 395 nm and a 455 nm cutoff emission filter.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02260451
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