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  • 1
    Electronic Resource
    Electronic Resource
    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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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Chromatographic determination of caffeine in pharmaceutical formulations using micellar mobile phases (1996)
    Springer
    Chromatographia 43 (1996), S. 149-152 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02292943
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Correlation between hydrophobicity of amino acids and retention data in reversed-phase liquid chromatography with micellar eluents (1995)
    Springer
    Chromatographia 41 (1995), S. 455-461 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Amino acids ; Hydrophobicity ; o-Phthalaldehyde-N-acetyl-L-cysteine derivatives ; Phenylthiohydantoin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Hydrophobic character is usually expressed in terms of the partition coefficient in 1-octanol-water (log PO/W). However, measurement of this coefficient is often problematic. Retention in micellar liquid chromatography is mainly due to hydrophobic interactions and can also be used as an index of hydrophobicity. A hydrophobicity scale was established with retention data foro-phthalaldehyde (OPA)-N-acetyl-L-cysteine (NAC) amino acid derivatives, using the glycine derivative as reference. Since the OPA-NAC derivatives only differ in the nature of R1 in the amino acid (R1CH(COOH)NH2), in the absence of electrostatic interactions the hydrophobic character of the substituent was responsible for retention. Linear relationships were obtained between log of the ratiok′ of amino acid derivatives:k′ of the glycine derivative for a given mobile phase, and logP O/W for the R1 substituent. Good correlations were also found for phenylthiohydantoin amino acid derivatives.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02318622
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Second-Derivative-Free Variant of the Chebyshev Method for Nonlinear Equations (2000)
    Springer
    Journal of optimization theory and applications 104 (2000), S. 501-515 
    Details
    ISSN: 1573-2878
    Keywords: Chebyshev method ; nonlinear equations in Banach spaces ; third-order methods ; multipoint iterations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract In this paper, we introduce a numerical method for nonlinear equations, based on the Chebyshev third-order method, in which the second-derivative operator is replaced by a finite difference between first derivatives. We prove a semilocal convergence theorem which guarantees local convergence with R-order three under conditions similar to those of the Newton-Kantorovich theorem, assuming the Lipschitz continuity of the second derivative. In a subsequent theorem, the latter condition is replaced by the weaker assumption of Lipschitz continuity of the first derivative.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004618223538
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  • 5
    Electronic Resource
    Electronic Resource
    Reduced Recurrence Relations for the Chebyshev Method (1998)
    Springer
    Journal of optimization theory and applications 98 (1998), S. 385-397 
    Details
    ISSN: 1573-2878
    Keywords: Chebyshev method ; nonlinear equations in Banach spaces ; third-order methods ; recurrence relations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract In this paper, we give sufficient conditions ensuring the convergence of the Chebyshev method in Banach spaces. We use a new system of recurrence relations which simplifies those given by Kantorovich for the Newton method or those given by Candela and Marquina for the Chebyshev and Halley methods.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022641601991
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    Paper (German National Licenses)
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