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  • 1
    ISSN: 1573-904X
    Keywords: quantitative analysis ; FTIR (DRIFT) ; Kubelka-Munk ; neutralization ; Carbopol® 974P NF
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. The purpose of this study was to develop an analytical method for the quantitative determination of the extent of neutralization of the carboxylic acid function in Carbopol® 974P NF using Diffuse Reflectance Fourier Transform Infrared Spectroscopy (DRIFT) with Kubelka-Munk function analysis. Methods. Carbopol® 974P NF is a high molecular weight, chemically crosslinked polymer of acrylic acid, that has the C=O stretching band of the unionized carboxylic acid function at 1695 cm−1. The quantitative determination of the extent of neutralization of the carboxylic acid function in Carbopol® 974P NF is based upon the asymmetrical C =O stretching of the carboxylate anion at 1570 cm−1 measured by DRIFT Spectroscopy. Results. To overcome spectral differences arising from sample preparation (powders, granules and tablets) and in an effort to increase the precision of the analytical method, the following approaches were used: (1) an internal standard, (2) first derivative of the spectrum to eliminate the effect of baseline drift and (3) the ratio of the first derivative of the C=O stretch of the carboxylate anion peak (1570 cm−1) in the neutralized Carbopol® 974P NF to that of the peak of the internal standard (866 cm−1). The above data treatment techniques proved to be superior to the usual methods of peak height or peak area. The calibration curve of the ratio of the first derivative (1570 cm−1/866 cm−1) was a linear function of the mass of sodium carboxylate over the range from 0.0% to 100.0% neutralization of the carboxylic acid function in Carbopol® 974P NF (Fig. la). No particle size or sample preparation effects were noted within the experimental error. Conclusions. DRIFT Spectroscopy using the Kubelka-Munk function is a powerful tool for the routine determination of the extent of neutralization of the carboxylic acid function in Carbopol® 974P NF in complex pharmaceutical formulations.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 20 (1982), S. 1505-1516 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Iodine azide adds to cyclohexene in acetonitrile or 4:1 methylene chloride/acetonitrile to give trans-1-azido-2-iodocyclohexane. In methylene chloride this reaction gives a mixture of the cis-and trans-iodoazides owing to competing radical addition. Iodine azide adds to 1-hexene in acetonitrile by an ionic mechanism to give a 3:1 mixture of the 2-azido-1-azido- and 1-azido-2-iodohexanes. Dehydroiodination of the model iodoazides proceeds smoothly with potassium t-butoxide in diethyl ether or THF in the presence of 5 mol % 18-crown-6 at room temperature, giving in the previous example a mixture of 2-azido- and trans-1-azidohexenes. Polybutadiene, carboxyterminated poly(acrylonitrile-co-butadiene), and hydroxy-terminated polybutadiene gave iodoazide derivatives with up to 96% of the theoretical maximum nitrogen content and strong azide IR absorption. High azidoiodination gave polymer with N3/I ratios slightly higher than unity while low percent azidoiodination led to polymer with N3/I ratios of as low as 2:3. All of the nitrogen introduced was in the form of azide function. Dehydroiodination gave polymers with vinyl azide functionality and caused loss of some of the azide groups. All the azidoiodinated polymers decomposed between 120 and 160°C. The dehydroiodinated materials were less stable, decomposing between 100 and 150°C. The temperature of initial decomposition decreased as azide content increased. Polymers with 〉55-60% of the theoretical maximum azide content were shock sensitive.
    Additional Material: 4 Tab.
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