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    In vitro release study of diltiazem hydrochloride from poly(vinyl pyrrolidone)/sodium alginate blend microspheres
    (Wiley, 2008) Sanli, Oya; Bicer, Emine; Isiklan, Nuran
    Polymeric blend microspheres of poly(vinyl pyrrolidone) (PVP) with sodium alginate (NaAlg) were prepared by cross-linking with calcium ions and used to deliver a calcium channel blocker drug, diltiazem hydrochloride (DT). The prepared microspheres were characterized by Fourier transform infrared spectroscopy and scanning electron microscopy. Scanning electron microscopy confirmed the spherical nature of the particles. Preparation conditions for the microspheres were optimized by considering the percentage entrapment efficiency, particle size, and swelling capacity. Effects of variables such as PVP/NaAlg ratio, molecular weight of PVP, cross-linker concentration, and drug/polymer ratio on the release of DT were discussed at two different pH values (1.2, 6.8) at 37 degrees C. It was observed that DT release from the microspheres decreased with increasing molecular weight of PVP and extent of cross-linking. However, DT release increased with increasing PVP content and drug/polymer ratio (d/p) of the blend microspheres. The highest DT release percentage was obtained as 99% for PVP/NaAlg ratio of 1/2 with d/p ratio of 1/2 at the end of 4 h. It was also observed from release results that DT delivery from the microspheres through the external medium are much higher at low pH (1.2) value than that of high pH (6.8) value. The drug release from the microspheres mostly followed Fickian transport. (c) 2007 Wiley Periodicals, Inc.
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    Permeation and separation characteristics of acetic acid-water mixtures by pervaporation through acrylonitrile and hydroxy ethyl methacrylate grafted poly(vinyl alcohol) membrane
    (Taylor & Francis Inc, 2006) Al-ghezawi, Nawash; Sanli, Oya; Işıklan, Nuran
    In this study, acrylonitrile ( AN) and hydroxyl ethyl methacrylate ( HEMA) were grafted onto poly( vinyl alcohol) (PVA) using cerium (IV) ammonium nitrate as initiator at 30 degrees C. The graft copolymer was characterized using the Fourier transform infrared spectroscopy ( FTIR) and elemental analysis. The grafted PVA membranes (PVA-g-AN/HEMA) were prepared by a casting method, and used in the separation of acetic acid-water mixtures by pervaporation. The effects of the membrane thickness, operating temperature, and feed composition on the permeation rate and separation factor for acetic acid-water mixtures were studied. Depending on the membrane thickness, the temperature and feed composition PVA-g-AN/HEMA membranes gave separation factors 2.26-14.60 and permeation rates of 0.18-2.07 kg/m(2)h. It was also determined that grafted membranes gave lower permeation rates and greater separation factors than PVA membranes. Diffusion coefficients of acetic acid-water mixtures were calculated from permeation rate values. The Arrhenius activation parameters were calculated for the 20 wt.% acetic acid content in the feed using the permeation rate and the diffusion data obtained at between 25-50 degrees C.