Limitation observed in the application of the three dimensional solubility parameters to the coating formulation of poly (3-hydroxybutyrate-hydroxyvalerate) systems

Purpose: Poly (3-hydroxybutyrate-hydroxyvalerate) displayed high dipole-dipole interaction, a high hydrogen bonding but low polar interaction, and was therefore expected to be miscible with solvents/plasticizers that exhibit similar pattern of cohesive interaction. To determine the applicability, or otherwise of the theory of the three dimensional solubility parameters to the formulation of poly (3-hydroxybutyrate-hydroxyvalerate) polymeric coating system, and hence identify any limitation in the application of the theory. This aspect was investigated in the study. Method: The structural group contribution method was employed to compute the partial and total solubility parameters of the compounds – the biopol polymer, a series of organic solvents and plasticizers. The computed partial solubility parameters included: dipole-dipole (dd), polar (dp) and hydrogen bonding (dh). Following a standard procedure in the literatures, the dd and dp values were combined to form a composite solubility parameter, dv: where dv = &#8730 &#948d 2+&#948p 2. A plot of dh versus dv gave the energy maps, which depicted the energy levels of the various compounds and from which the miscibility of the compounds were predicted. The closer the position of the solvent or plasticizer to the polymer in the map, the greater, the probability of mixing. Cast films of the various polymeric formulations were made and examined for homogeneity by scanning electron microscopy. Results: It was possible to select suitable plasticizers that were miscible with the polymer by applying theory of solubility parameters. The prediction for the solvents was, however, erroneous and this may be attributable to the inability of the dv parameter to clearly reflect the differences between the dd and dp interactions of the polymer on the one hand and those of the various solvents in all situations on the other hand. This means that in certain instances, the dv values of the polymer and the solvents were similar even though their dd and dp interactions were dissimilar. Conclusion: The analysis of the data showed that the composite solubility parameter dv of compounds could be similar even though the actual energies of dd and dp interactions are different. This is a limitation in the application of the theory of the three dimensional solubility parameters. Keywords: keyword; keyword; keyword > Tropical Journal of Pharmaceutical Research Vol. 4 (1) 2005: pp. 355-36

Electron Loss from 1.4-MeV / u U\u3csup\u3e4,6,10+\u3c/sup\u3e Ions Colliding with Ne, N₂, and Ar Targets

Absolute, total, single- and multiple-electron-loss cross sections are measured for 1.4-MeV / u U4,6,10+ ions colliding with neon and argon atoms and nitrogen molecules. It is found that the cross sections all have the same dependence on the number of electrons lost and that multiplying the cross sections by the initial number of electrons in the 6s, 6p, and 5f shells yields good agreement between the different projectiles. By combining the present data with previous measurements made at the same velocity, it is shown that the scaled cross sections slowly decrease in magnitude for incoming charge states between 1 and 10, whereas the cross sections for higher-charge-state ions fall off much more rapidly

Plutajuće matriks tablete: Dizajniranje i optimizacija kombiniranjem polimera

The purpose of the present study was to develop an optimized gastric floating drug delivery system (GFDDS) containing domperidone as a model drug. Box-Behnken design was employed in formulating the GFDDS with three polymers: hydroxypropyl methylcellulose K4M (HPMC K4M) (X1), Carbopol 934P (X2) and sodium alginate (X3), as independent variables. Floating lag time (FLT), total floating time (TFT), time required to release 50% of the drug (t50) and diffusion exponent (n) were selected as dependent variables. Seventeen formulations were prepared, dissolution data obtained was fitted to the power law and floating profiles were analyzed. HPMC loading was found to be significant for floating properties. Carbopol loading had a negative effect on floating properties but was found helpful in controlling the release rate of the drug. No significant effect of sodium alginate on floating properties was observed but it was important for gel formation. The quadratic mathematical model developed could be used to predict formulations with desired release and floating properties.Cilj rada bio je razvoj i optimizacija plutajućih sustava za isporuku lijekova u želucu (GFDDS) s domperidonom kao modelom lijeka. Box-Behnkenovo dizajniranje korišteno je u formuliranju GFDDS. Nezavisne varijable u dizajniranju bila su tri polimera: hidroksipropil metilceluloza K4M (HPMC K4M) (X1), Carbopol 934P (X2) i natrijev alginat (X3), a zavisne varijable usporeno vrijeme plutanja (FLT), ukupno vrijeme plutanja (TFT), vrijeme potrebno za oslobađanje 50% lijeka (t50) i difuzijski eksponent (n). Pripravljeno je ukupno sedamnaest formulacija. Analizirani su podaci o oslobađanju ljekovite tvari. Količina HPMC značajno utječe na svojstva plutanja, dok količina karbopola ima negativni učinak na svojstvo plutanja, ali kontrolira oslobađanje ljekovite tvari. Natrijev alginat nema značajni učinak na svojstva plutanja, ali utječe na stvaranje gela. Kvadratni matematički model može se upotrijebiti za predviđanje formulacija sa željenim profilom oslobađanja i svojstvima plutanja

Kinetics and Mechanism for Reversible Chloride Transfer between Mercury(II) and Square-Planar Platinum(II) Chloro Ammine, Aqua, and Sulfoxide Complexes. Stabilities, Spectra, and Reactivities of Transient Metal-Metal Bonded Platinum-Mercury Adducts

The Hg2+(aq-) and HgCl+(aq-)assisted aquations of [PtCl4]2- (1), [PtCl3(H2O)]- (2), cis-[PtCl2(H2O)2] (3), trans-[PtCl2(H2O)2] (4), [PtCl(H2O)3]+ (5), [PtCl3Me2SO]- (6), trans-[PtCl2(H2O)Me2SO] (7), cis-[PtCl(H2O)2Me2-SO]+ (8), trans-[PtCl(H2O)2Me2SO]+ (9), trans-[PtCl2(NH3)2] (10), and cis-[PtCl2(NH3)2] (11) have been studied at 25.0 °C in a 1.00 M HClO4 medium buffered with chloride, using stopped-flow and conventional spectrophotometry. Saturation kinetics and instantaneous, large UV/vis spectral changes on mixing solutions of platinum complex and mercury are ascribed to formation of transient adducts between Hg2+ and several of the platinum complexes. Depending on the limiting rate constants, these adducts are observed for a few milliseconds to a few minutes. Thermodynamic and kinetics data together with the UV/vis spectral changes and DFT calculations indicate that their structures are characterized by axial coordination of Hg to Pt with remarkably short metal-metal bonds. Stability constants for the Hg2+ adducts with complexes 1-6, 10, and 11 are (2.1 ± 0.4) x 104, (8 ± 1) x 102, 94 ± 6, 13 ± 2, 5 ± 2, 60 ± 6, 387 ± 2, and 190 ± 3 M-1, respectively, whereas adduct formation with the sulfoxide complexes 7-9 is too weak to be observed. For analogous platinum(II) complexes, the stabilities of the Pt-Hg adducts increase in the order sulfoxide ' aqua < ammine complex, reflecting a sensitivity to the π-acid strength of the Pt ligands. Rate constants for chloride transfer from HgCl+ and HgCl2 to complexes 1-11 have been determined. Second-order rate constants for activation by Hg2+ are practically the same as those for activation by HgCl+ for each of the platinum complexes studied, yet resolved contributions for Hg2+ and HgCl+ reveal that the latter does not form dinuclear adducts of any significant stability. The overall experimental evidence is consistent with a mechanism in which the accumulated Pt(II)-Hg2+ adducts are not reactive intermediates along the reaction coordinate. The aquation process occurs via weaker Pt-Cl-Hg or Pt-Cl-HgCl bridged complexes