Salt addition effect on partition coefficient of some phenolic compounds constituents of olive mill wastewater in 1-octanol-water system at 298.15 K

The 1-octanol-water partition coefficient is an important property to measure the hydrophobicity of organic compounds, which has been demonstrated to be a parameter in studying the conformation of biomolecules in aqueous solutions. For biological systems, electrolytes play an important role in thermodynamic properties. The salt addition effect on the distribution of phenolic compounds between water and 1-octanol at 298.15 K has been studied. The phenolic compounds used were vanillic acid, protocatechuic acid, vanillin, tyrosol, cathecol, caffeic acid and syringic acid, and the considered salts were potassium chloride, sodium chloride and lithium chloride. The influence of both the concentration and size of the added salt on the partition coefficient (K _ow) have been considered. This study shows a salting in with the following decreasing order: LiCl > NaCl > KCl. The Gibbs energies of transfer of phenolic compounds (168–1) form chloride solutions to organic phase have been calculated using experimental 1-octanol-water partition coefficients.     

三元体系NaCl-KCl-H2O35℃活度系数的研究

研究了35℃ NaCl-KCl-H2O三元体系的活度系数.用Na+、 K+和Cl-的离子选择性电极分别测得了(0.1～ 1.5 mmol/L)不同离子强度下该体系中NaCl和KCl的平均活度系数.回归了该体系Pitzer方程的相互作用参数.实验值与计算值最大相对误差为5.6%,而平均相对误差为2.3%.     

A new high-throughput method utilizing porous silica-based nano-composites for the determination of partition coefficients of drug candidates

We show that highly porous silica-based nanoparticles prepared via micro-emulsion and sol-gel techniques are stable colloids in aqueous solution. By incorporating a magnetic core into the porous silica nano-composite, it is found that the material can be rapidly separated (precipitated) upon exposure to an external magnetic field. Alternatively, the porous silica nanoparticles without magnetic cores can be equally separated from solution by applying a high-speed centrifugation. Using these silica-based nanostructures a new high-throughput method for the determination of partition coefficient for water/n-octanol is hereby described. First, a tiny quantity of n-octanol phase is pre-absorbed in the porous silica nano-composite colloids, which allows an establishment of interface at nano-scale between the adsorbed n-octanol with the bulk aqueous phase. Organic compounds added to the mixture can therefore undergo a rapid partition between the two phases. The concentration of drug compound in the supernatant in a small vial can be determined by UV-visible absorption spectroscopy. With the adaptation of a robotic liquid handler, a high-throughput technology for the determination of partition coefficients of drug candidates can be employed for drug screening in the industry based on these nano-separation skills. The experimental results clearly suggest that this new method can provide partition coefficient values of potential drug candidates comparable to the conventional shake-flask method but requires much shorter analytical time and lesser quantity of chemicals.     

Determination of polydimethylsiloxane-air partition coefficients using headspace sorptive extraction

Polydimethylsiloxane-air partition coefficients (K(PDMS-A)) were determined using direct headspace analysis and headspace sorptive extraction (HSSE) with polydimethylsiloxane-coated (PDMS) stir bars. The partition coefficients were investigated for three compounds, p-dichlorobenzene (PDCB), naphthalene and camphor, all of which sublimate at room temperature and find use as moth repellents. In order to determine the K(PDMS-A) values of these compounds, the air concentration and the concentration present on PDMS, both at equilibrium, were measured. The results indicate that PDMS-air partition coefficients are proportional to octanol-air partition coefficients. Thus, the latter could be used to estimate the extraction efficiency of PDMS for these compounds in air. Alternatively, octanol-air partition coefficients for organic compounds could be estimated from the PDMS-air partition coefficient values. As expected, the PDMS-air (or octanol-air) partition coefficient increased with decreasing temperature. Importantly, the partition coefficients determined at saturated vapor pressures were lower than the values determined at lower analyte concentrations, with the differences being greater for compounds with larger partition coefficients. Consequently, caution should be exercised when applying K(PDMS-A) values determined at high analyte concentrations to measurements at lower concentrations, especially when the partition coefficients are large.     

On the volatility and disproportionation of hypoiodous acid

The partition coefficient of hypoiodous acid at 20 °C has been determined to be 930. This determination is based on measured values of the instantaneous iodine partition coefficient /IPC/ vs. time after the introduction of molecular iodine into an air-water system at pH=9.     

Experimental Examination of Solubility and Lipophilicity as Pharmaceutically Relevant Points of Novel Bioactive Hybrid Compounds

The important physicochemical properties of three novel bioactive hybrid compounds with different groups (-CH₃, -F and -Cl) were studied, including kinetic and thermodynamic solubility in pharmaceutically relevant solvents (buffer solutions and 1-octanol) as well as partition coefficient in system 1-octanol/buffer pH 7.4. The aqueous solubility of these chemicals is poor and ranged from 0.67 × 10⁻⁴ to 1.98 × 10⁻³ mol·L⁻¹. The compounds studied are more soluble in the buffer pH 2.0, simulating the gastrointestinal tract environment (by an order of magnitude) than in the buffer pH 7.4 modelling plasma of blood. The solubility in 1-octanol is significantly higher; that is because of the specific interactions of the compounds with the solvent. The prediction solubility behaviour of the hybrid compounds using Hansen’s three-parameter approach showed acceptable results. The experimental solubility of potential drugs was successfully correlated by means of two commonly known equations: modified Apelblat and van’t Hoff. The temperature dependencies of partition coefficients of new hybrids in the model system 1-octanol/buffer pH 7.4 as a surrogate lipophilicity were measured by the shake flask method. It was found that compounds demonstrated a lipophilic nature and have optimal values of partition coefficients for oral absorption. Bioactive assay manifested that prepared compounds showed antifungal activities equal to or greater than fluconazole. In addition, the thermodynamic aspects of dissolution and partition processes have been examined. Bioactive assay manifested that prepared compounds showed antifungal activities equal to or greater than the reference drug.     

Solvation in octanol: parametrization of the continuum MST model

This study reports the parametrization of the HF/6‐31G(d) version of the MST continuum model for n‐octanol. Following our previous studies related to the MST parametrization for water, chloroform, and carbon tetrachloride, a detailed exploration of the definition of the solute/solvent interface has been performed. To this end, we have exploited the results obtained from free energy calculations coupled to Monte Carlo simulations, and those derived from the QM/MM analysis of solvent‐induced dipoles for selected solutes. The atomic hardness parameters have been determined by fitting to the experimental free energies of solvation in octanol. The final MST model is able to reproduce the experimental free energy of solvation for 62 compounds and the octanol/water partition coefficient (log P_ow) for 75 compounds with a root‐mean‐square deviation of 0.6 kcal/mol and 0.4 (in units of log P), respectively. The model has been further verified by calculating the octanol/water partition coefficient for a set of 27 drugs, which were not considered in the parametrization set. A good agreement is found between predicted and experimental values of log P_o/w, as noted in a root‐mean‐square deviation of 0.75 units of log P. © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 1180–1193, 2001     

Spectrophotometric studies on the interactions of C.I. Basic Red 9 and C.I. Acid Blue 25 with hexadecyltrimethylammonium bromide in cationic surfactant micelles

Interactions between cationic dye-cationic surfactant and anionic dye-cationic surfactant systems were investigated in aqueous solutions using spectrophotometric method at 288.15, 298.15, 308.15 and 318.15 K. C.I. Basic Red 9 (BR9) and C.I. Acid Blue 25 (AB25) were used as cationic and anionic dyes, respectively, and hexadecyltrimethylammonium bromide (HDTMABr) was selected as cationic surfactant in this study. Although there was an interaction between the AB25 and the HDTMABr molecules, an interaction between the BR9 and HDTMABr did not occur due to the electrostatic repulsion forces. Binding constants and partition coefficients between the micellar and the bulk water phases for the AB25-HDTMABr system were calculated from the changes in absorbance values and the critical micelle concentrations at different temperatures. It was found that the values of binding constant and partition coefficient decreased with increasing temperature. Thermodynamic parameters (ΔG⁰, ΔH⁰ and ΔS⁰) were determined for the binding and partition processes of AB25-HDTMABr system. It was concluded from ΔG⁰ values that the binding of AB25 to HDTMABr occurred spontaneously. In addition, the binding and partition processes were exothermic.     

NaCl对烷基苯磺酸盐Gemini表面活性剂水溶液性质的影响

采用旋滴法测定了烷基苯磺酸盐Gemini表面活性剂Ia水溶液与正庚烷的界面张力,用超微电极循环伏安法测定了水溶液中Ia的胶束扩散系数.结果发现,NaCl的加入能够使界面张力降低2倍左右,使Ia的胶束扩散系数变大;Ia浓度增大,胶束扩散系数变小,而NaCl浓度增大,胶束扩散系数变大.这些变化说明NaCI的加入使得Ia胶束大小发生了变化.这是由于NaCl的加入降低了Ia离子头基之间的静电斥力,使得Ia分子排列更加紧密,更有效降低了油水的界面张力,使胶束形状变小;同时胶束表面电荷得到中和,胶束的静电斥力相应减小,胶束流动性相应增加,从而表现出较大的胶柬扩散系数.     

脂质体毛细管电泳方法评价有机化合物在体内的吸收

有机化合物在脂质体毛细管电泳中的保留值大小可以体现化合物的亲脂性大小。比较了9种有机化合物在脂质体毛细管电泳中脂质体/水的疏水参数(log Plw)(由保留因子k的对数值(log k)转化而来)及其在正辛醇/水体系中的疏水参数(log Pow)与其渗透系数的对数值(log Pm)的相关性,log Plw与log Pm的相关系数为0.94,log Pow与log Pm的相关系数仅为0.78,说明脂质体/水模型较正辛醇/水模型更加接近于生物膜模型。脂质体毛细管电泳可以快速、准确地测定化合物的疏水参数,通过化合物在脂质体毛细管中的保留可以快速、初步地预测化合物在体内的吸收情况。     

Development of an automatic estimation system for both the partition coefficient and aqueous solubility

Summary A computer program has been developed for estimating both the partition coefficient between 1-octanol and water phases and the aqueous solubility from the structural formula. This system is an extended version of a previously described program entitled CHEMICALC for the automatic estimation of the partition coefficient. The aqueous solubility is estimated via two pathways. The first is based on the linear relationship between logarithms of the aqueous solubilities of 497 compounds and their estimated 1-octanol/water partition coefficients. In the second, combined handling of two available group contribution methods of Irmann [Chem. Ing. Tech., 37 (1965) 789] and Wakita et al. [Chem. Pharm. Bull., 34 (1986) 4663] is adopted according to compound type. Some revisions and extensions of the methods for estimating the aqueous solubility have been made in both pathways, and the accuracy of the estimated aqueous solubilities for 497 compounds is discussed.     

Countercurrent Chromatography for the Measurement of the Hydrophobicity of Sulfonamide Amphoteric Compounds

Octanol-water partition coefficients (P _o/w ) of 17 sulfonamides (SAs) were determined by countercurrent chromatography (CCC). The measured P _o/w values were in the 0.002–46 range (–2.65 < log P _o/w < 1.7). The lipophility of these compounds depends on the pH showing a maximum for intermediate values. The apparent P _o/w coefficients of SAs were obtained at 5 pH values: 2, 3, 5, 7 and 11, using 0.01 M ammonium phosphate octanol saturated buffers. A theoretical model linking these values with pH for amphoteric compounds was checked and verified. Often the P _o/w coefficients of the molecular forms obtained with the CCC method differ significantly from literature values obtained using softwares and/or from experimental values calculated with extrapolation. The CCC method allows also the determination of the P _o/w coefficients of the ionic forms of the SAs, cationic forms at low pH values and anionic forms at elevated pHs. The acidity constants were also estimated using the theoretical model. Relationships between SA retention factors obtained by RPLC and hydrophobicity were also discussed.     

A method for measuring infinite-dilution partition coefficients of volatile compounds between the gas and liquid phases of aqueous systems

Vejrosta, J., Novák, J. and Jönsson, J.Å., 1982. A method for measuring infinite-dilution partition coefficients of volatile compounds between the gas and liquid phases of aqueous systems. Fluid Phase Equilibria, 8: 25–35.A method has been developed for measuring the partition coefficients of volatile compounds between the gas and liquid phases of aqueous systems, based on the direct analysis of both phases. A gas mixture containing a known proportion of a volatile compound is drawn through the liquid (water) until equilibrium is established. A defined volume of the liquid phase is then withdrawn through a porous-polymer trap while maintaining the system at equilibrium. The residual water in the trap is then expelled by a stream of nitrogen gas, and the deposit remaining is thermally desorbed and analyzed by gas chromatography. This approach, together with an experimental technique for producing gas mixtures containing an accurately known concentration of hydrocarbon at low values, makes it possible to determine accurately the partition coefficients of low-solubility compounds, such as for hydrocarbons in aqueous systems, at very low solute concentrations in the system. The method has been verified by measuring the partition coefficient of hexane between the gas and liquid phases of an aqueous system at various concentrations and temperatures.     

Solvatochromic relationship: Prediction of distribution of ionic solutes in aqueous two-phase systems

Partition ratios of several ionic compounds in 20 different polymer/polymer aqueous two-phase systems (ATPS) containing 0.15 M NaCl in 0.01 M phosphate buffer, pH 7.4, were determined. The differences between the electrostatic properties of the phases in all the ATPS were estimated from partitioning of the homologous series of dinitrophenylated-amino acids. Also the solvatochromic solvent parameters characterizing the solvent dipolarity/polarizability (π*), solvent hydrogen-bond donor acidity (α), and solvent hydrogen-bond acceptor basicity (β) of aqueous media were measured in the coexisting phases of the ATPS. The solute-specific coefficients for the compounds examined were determined by the multiple linear regression analysis using the modified linear solvation energy relationship equation. The minimal number of ATPS necessary for determination of the coefficients was established and 10 ATPS were selected as a reference ATPS set. The solute-specific coefficients values obtained with this reference set of ATPS were used to predict the partition ratios for the compounds in 10 ATPS not included in the reference set. The predicted partition ratios values were compared to those determined experimentally and found to be in good agreement. It is concluded that the presented model of solute–solvent interactions as the driving force for solute partitioning in polymer/polymer ATPS describes experimental observations with 90–95% accuracy.     

Hydrophobic nature of sugars as evidenced by their differential affinity for polystyrene gel in aqueous media

Partition coefficients K _av for the partition of sugars between a polystyrene gel and aqueous solvents were determined. The results show that monosaccharides have different affinities for polystyrene. Their K _av values increase markedly in NaCl solution but reduce to nearly the same value in solutions of NaSCN and LiSCN, both highly chaotropic salts. The K _av of maltodextrins increase with their molecular weight. These partition peculiarities are attributed to the hydrophobic nature of sugars presumably due to their CH surface. The order of increasing hydrophobicity based on K _av is: D-galactose < D-glucose < D-mannose < (D-arabinose, D-xylose) < D-ribose. This order is consistent with that based on the free energy change pertaining to the transfer of sugar molecules from water to 1-butanol.     

Porous alumina-based fluorous liquid membranes: Dependence of transport on fluorous solvent

We report here the properties of supported fluorous liquid membranes based on porous alumina. The alumina is first rendered compatible with fluorous solvents by surface modification with an oligomeric perfluoropropylene oxide-based carboxylic acid, Krytox 157FSH. After modification, simply dipping the porous alumina membrane into a perfluorinated solvent results in a supported liquid membrane with high selectivity for fluorous compounds. Two homologous series of compounds differing in the number of -CF₂- groups were investigated, namely esters of cinnamyl alcohol and the analogous naphthyl derivative with 2H,2H,3H,3H-perfluoroalkanoic acids (HOOC-(CH₂)₂-(CF₂)_m−1CF₃, m = 2, 4, 6 and 8). Four perfluorinated membrane solvents (FC-77, PF-5080, FC-3283 and FC-43) were investigated. In FC-3283, the permeabilities, which are the products of a diffusion coefficient and a partition coefficient in the solution-diffusion model, of cinnamyl alcohol derivatives are 3.62 ± 0.36 times greater than those of the analogous naphthyl compounds for the solutes containing the same perfluorinated chain. Permeability, P, increases as the perfluorinated chain length increases in all of the perfluorinated solvents. Values of log(P) vs m are linear with a slope of 0.147 ± 0.002 but with different intercepts for the various solvents. Independent measurements of the partition coefficients of the solutes between the source/receiving phase solvent, ethanol, and the fluorous solvents reveal that the selectivity behavior is dominated by partitioning rather than diffusion. The free energy of transfer of a -CF₂- group (ethanol to perfluorinated solvents) is −1.1 kJ/mol. Despite the fact that the solvents are mixtures, not pure liquids, the partition coefficients are well correlated with values calculated based on group contributions with ‘mobile order and disorder’ theory. The diffusion coefficients of four solutes in four membrane solvents were also determined based on the solution-diffusion model. The Stoke-Einstein equation shows satisfactory estimation of experimental results.     

Estimation of trace elements in water matrix from photon attenuation coefficients

The method of elemental analysis based on the measurement of attenuation coefficient has been used to estimate the impurity introduced in a water matrix using a scintillation detector with a single channel analyser. For a 2% change in the mass attenuation coefficient the minimum detectable fractions of impurities were estimated to be of the order of 625–1250 μg/g for uranium and thorium compounds at photon energies 32.1 and 59.5 keV.