Comparison of Dissolution Profiles of Furosemide Tablets Available in the Argentinian Market
Pages 186-193
Yong K. Han, Laura D. Simionato, Romina G. Calvo, María B. Mattei and Adriana I. Segall

DOI: http://dx.doi.org/10.6000/1929-5030.2014.03.04.1

Published: 17 December 2014

Abstract: In this work dissolution profiles of furosemide tablets of nine commercial products marketed in Argentine were evaluated. All brands fulfill the specifications of dissolution test of USP. Comparison of dissolution profiles were carried out by model-dependent and model independent approaches. Results obtained via model-dependent approach show a first order drug release mechanism especially for Brand I (reference) and Brand IV. Results obtained via model-independent approach show that there was not significant difference in Dissolution efficiency between the reference product and Brands II, III and IV and in Mean dissolution time between the reference product and Brands II, III, IV and V. Using fit factors, only Brands I and III were similar.

Solubility of CO₂ in Brine and Reservoir Oil for Depleted Reservoirs in China
Pages 194-201
Ke Zhang, Desheng Ma, Shi Li and Xinglong Chen

DOI: http://dx.doi.org/10.6000/1929-5030.2014.03.04.2

Published: 17 December 2014

Abstract: Many countries play an important role to carbon capture, utilization, and Storage (CCUS) to reduce emission. Geological storage is an important approach to cope with climate change. Live oil combined with saline aquifers and gas reservoirs are among the candidates for carbon dioxide (CO₂) sequestration, owing to their proven sealing capabilities and characterization. CO₂ mainly from power industrial was captured to improve oil recovery in some oilfields in China, and solubility is a key factor to evaluate storage ability of reservoir and saline aquifer. In this paper, CO₂ sequestration mechanisms in deplete reservoir and saline aquifer were explained. An experimental method to test solubility of CO₂ in emulsion system of liver oil and brine was developed. The experimental results showed that with the salinity increased, the solubility of CO₂ in reservoir oil increased slightly, and the solubility of CO₂ in brine decreased. Salinity has little impact on solubility of CO₂ in reservoir oil. With the pressure increased, the solubility of CO₂ in reservoir oil and brine both increased. Molecular diameter of reservoir oil and white oil have inverse proportion relationship with the solubility Research on solubility of CO₂ in brine and reservoir oil for depleted reservoir in China enabled us to better predict and deal with the challenges for rapid development of carbon storage.

The Radical-Chain Addition to Double Molecular Bonds by the Nonbranched-Chain Mechanism: Low-Reactive Free Radicals Shortening Kinetic Chains
Pages 202-222
Michael M. Silaev

DOI: http://dx.doi.org/10.6000/1929-5030.2014.03.04.3

Published: 17 December 2014

Abstract: Five reaction schemes are suggested for the initiated nonbranched-chain addition of free radicals to the multiple bonds of the unsaturated compounds. The proposed schemes include the reaction competing with chain propagation reactions through a reactive free radical. The chain evolution stage in these schemes involves three or four types of free radicals. One of them is relatively low-reactive and inhibits the chain process by shortening of the kinetic chain length. Based on the suggested schemes, nine rate equations (containing one to three parameters to be determined directly) are deduced using quasi-steady-state treatment. These equations provide good fits for the nonmonotonic (peaking) dependences of the formation rates of the molecular products (1:1 adducts) on the concentration of the unsaturated component in binary systems consisting of a saturated component (hydrocarbon, alcohol, etc.) and an unsaturated component (olefin, allyl alcohol, formaldehyde, or dioxygen). The unsaturated compound in these systems is both a reactant and an autoinhibitor generating low-reactive free radicals. A similar kinetic description is applicable to the nonbranched-chain process of the free-radical hydrogen oxidation, in which the oxygen with the increase of its concentration begins to act as an oxidation autoingibitor (or an antioxidant). The energetics of the key radical-molecule reactions is considered.

Solvatochromic Parameters of the Binary Mixtures of Imidazolium Chloride Ionic Liquid Plus Molecular Solvent
Pages 223-230
Jingyi Hu, Wei Zhu, Qiwei Yang, Guoping Qian and Huabin Xing

DOI: http://dx.doi.org/10.6000/1929-5030.2014.03.04.4

Published: 17 December 2014

Abstract: Imidazolium-based chloride ionic liquids (ILs) have exhibited remarkable performance in several important applications such as biomass dissolution and extraction, but their large viscosity is a non-negligible problem. Adding molecular co-solvents into chloride ILs is effective in reducing viscosity; nevertheless, understanding of the accompanied change of thermodynamic polarity is quite few. Therefore, in this work we reported three Kamlet-Taft solvatochromic parameters, including dipolarity/polarizability (ð*), hydrogen-bond acidity (α) and hydrogen-bond basicity (β), for the binary mixtures of several imidazolium-based chloride ILs plus either dipolar protic solvents (water and methanol) or dipolar aprotic solvents (dimethyl sulfoxide, N,N-dimethylformamide and acetonitrile). The results demonstrated that those parameters could be altered by the structure of IL and type of co-solvent owing to the solute-solvent and solvent-solvent interactions. The structure of alkyl chain of cation had considerable impact on the ð* variation of IL aqueous solution against IL concentration but hardly affected other mixtures. Moreover, remarkable preferential solvation of probes was observed for β and α in the mixtures of IL and dipolar aprotic co-solvents, whereas the hydrogen-bond interactions between IL and dipolar protic co-solvent enabled the preferential solvation to be alleviated and resulted in more linear variation of β and α against the molar fraction of IL. The results not only contribute to a better understanding of the effect of co-solvent on imidazolium-based chloride ILs, but also are instructive for improving the thermodynamic performance of IL-based applications via providing IL+co-solvent mixtures with desirable physicochemical properties.

Nonbranched-Chain Oxidation: Low-Reactive RO^•₄ and HO^•₄ 1:2 Adduct Radicals Shortening Kinetic Chains
Pages 231-241
Michael M. Silaev

DOI: http://dx.doi.org/10.6000/1929-5030.2014.03.04.5

Published: 17 December 2014

Abstract: New reaction scheme is suggested for the initiated nonbranched-chain addition of free radicals to the multiple bond of the molecular oxygen. The scheme includes the reaction competing with chain propagation reactions through a reactive free radical. The chain evolution stage in this scheme involves a few of free radicals, one of which (tetraoxyl) is relatively low-reactive and inhibits the chain process by shortening of the kinetic chain length. Based on the proposed scheme rate equations (containing one to three parameters to be determined directly) are deduced using quasi-steady-state treatment. The kinetic description with use the obtained rate equations is applied to the γ-induced nonbranched-chain processes of the free-radical oxidation of liquid o-xylene at 373 K and hydrogen dissolved in water containing different amounts of oxygen at 296 K. In these processes the oxygen with the increase of its concentration begins to act as an oxidation autoingibitor (or an antioxidant), and the rate of peroxide formation as a function of the dissolved oxygen concentration has a maximum. The heat effects are compared for the overall reactions of dissociation of simple alkylperoxyl (exothermic) and alkoxyl (endothermic) free radicals in the gas phase. Possible nonchain pathways of the free-radical oxidation of hydrogen and the routes of ozone decay from the energetic standpoint via the reaction with the hydroxyl free radical in the upper atmosphere (including the addition yielding the hydrotetraoxyl free radical, which can be an intermediate in the sequence of conversions of biologically hazardous UV radiation energy) were examined. The energetics of the key radical-molecule reactions is considered.