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  • 1
    Electronic Resource
    Electronic Resource
    Separation Speed in Thermal Field Flow Fractionation (1994)
    s.l. : American Chemical Society
    Analytical chemistry 66 (1994), S. 3073-3080 
    Details
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ac00091a014
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  • 2
    Electronic Resource
    Electronic Resource
    Practical experience with organic solvent flow field-flow fractionation (1996)
    Springer
    Chromatographia 42 (1996), S. 409-415 
    Details
    ISSN: 1612-1112
    Keywords: Flow field-flow fractionation ; Organic solvents ; Polymer fractionation ; Particle size determination ; Polystyrene ; Polystyrene latexes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Several types of membrane have been tested for use in organic solvent flow field-flow fractionation in an asymmetric channel. The practical problems most commonly encountered were leakage of air and solvent through the support layer on which the membranes are cast, and unequal swelling of the membrane and the support layer in the organic solvent, leading to ridging of the membrane in the channel. Three types of membrane were found suitable for the separation of polystyrene standards with tetrahydrofuran as solvent. The best results were obtained with a fluoropolymer membrane. Fair agreement was found between theory and practice for the dependence of retention times on the relative molecular mass of the standards and on the flow regime. Use of scanning electron microscopy revealed that for a number of the membrane materials some pores were much larger than expected on the basis of the indicated molecular weight cut-off. Whereas these materials could not be used for the fractionation of soluble polymers, they could be applied with some success to the separation of solid latex and silica particles. A PTFE membrane could be used for the separation of latexes and silica particles suspended in acetonitrile as carrier liquid. In general, however, the retention times of these particles were shorter than theoretically predicted.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02272132
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  • 3
    Electronic Resource
    Electronic Resource
    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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  • 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
    Abstracts of papers (1985)
    Springer
    Pharmacy world & science 7 (1985), S. 86-90 
    Details
    ISSN: 1573-739X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02106135
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  • 6
    Electronic Resource
    Electronic Resource
    Determination of aldehydes in water samples by capillary electrophoresis after derivatization with hydrazino benzene sulfonic acid (1998)
    Springer
    Chromatographia 48 (1998), S. 807-810 
    Details
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Aldehydes ; Hydrazino benzene sulfonic acid ; Water analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A method has been developed for the analysis of environmentally important aldehydes in rain water. The method is based on the derivatization of the aldehydes with hydrazino benzene sulfonic acid, separation of the hydrazones formed by capillary electrophoresis and UV detection at 280 nm. Derivatization was shown to be complete in 15 min at 50°C. The aldehyde derivatives could be separated from each other and from the excess of reagent using a pH 9 borate buffer as background electrolyte, with an analysis time of less than 6 min. The repeatability was better than 0.5% for the peak mobilities and in the order of 2–5% for the peak areas. Detection limits of 0.8–3 μmol L−1 (0.02–0.2 ppm) were obtained. The method was applied for the determination of formaldehyde and acetaldehyde in rain water samples.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02467652
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  • 7
    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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  • 8
    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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  • 9
    Electronic Resource
    Electronic Resource
    An electrochemical detector cell for open tubular liquid chromatography and capillary electrophoresis (1993)
    Springer
    Chromatographia 37 (1993), S. 79-85 
    Details
    ISSN: 1612-1112
    Keywords: Open tubular liquid chromatography ; Capillary electrophoresis ; Electrochemical detection ; Amino acid analysis ; Catecholamine analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An electrochemical detector cell has been developed for micro-flow separation systems (OTLC, CE). The cell contains two electrodes, a disk-shaped working electrode made from a carbon fiber bundle, and a tubular Ag/AgCl quasi-reference electrode. The effective cell volume and the coulometric yield have been determined, for different electrode diameters and at different flow rates, in an OTLC system. An effective cell volume of less than 1 nl was observed. The applicability of the cell was demonstrated with the detection of OPA-derivatized amino acids. For use in CE, the cell was equipped with an additional compartment, housing a semi-permeable joint for the decoupling of the high electric field used for the electrophoretic separation. Results are shown on the determination of catecholamines by CE with electrochemical detection. Detection limits with both OTLC and CE were well below 1 fmole.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02272193
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  • 10
    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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