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PubMed1987

The limits of bioaccumulation of organic pigments in fish: their relation to the partition coefficient and the solubility in water and octanol.

A reliable experimental determination of the partition coefficient Pow of organic pigments is met with serious difficulties due to the extremely low water solubilities of these compounds. Therefore, the Pow values and the water solubilities were calculated for 11 typical organic pigments and some disperse dyes as well. The calculated Pow values of the pigments were very high predicting bioaccumulation factors (BF) several orders of magnitude above 100. Based on recent studies confirming that n-octanol simulates lipids in their solubilizing effect on organic chemicals, the solubilities of these organic pigments in n-octanol were measured in order to estimate their potential for lipid storage. The very low solubility values indicate that in spite of the very high predicted BF such pigments cannot build up concentrations in lipids (hence in fish) which could be of concern considering their generally low toxicity and the extremely small amounts entering the environment. Therefore, there should be no need to perform a fish bioaccumulation test for assessing the bioaccumulation potential of such compounds, provided they show comparable solubility characteristics as the pigments investigated in this study.

Animals↗
PubMed1994

Mechanized determination of n-octanol/water partition constants using liquid-liquid segmented flow extraction.

A simple and rapid method for the determination of partition constants in the n-octanol/water system is presented. The substance under study is dissolved in n-octanol or water, and injected into a stream of the corresponding phase. Liquid-liquid segmented flow is utilized for equilibration of the two phases and after equilibration a fraction of the aqueous phase is separated with the aid of a hydrophilic membrane. The amount of substance in the aqueous phase is measured spectrophotometrically. The measurements are repeated at a small number of different phase flow ratios and the results obtained are plotted against these ratios. From slope and intercept for the regression line through these points the conditional partition constant, D', can be calculated. A simplified procedure using only two measurements, one of which is obtained with the flow rate of organic phase set to 0, can also be used. Partition constants in the range 0.48 < D < 873 (-0.32 < log D < 2.94) have been determined using this system. The precision, measured as relative standard deviation (RSD) is below 15%, corresponding to a standard deviation of +/- 0.1 log unit or less over the range of measurement. Measured values correspond to literature values within 0.07 log units. The time needed for a determination is about 15 min per substance, in many cases even shorter and the sample consumption is, in most cases, less than 1 mg.

Flow Injection Analysis↗
PubMed2005

Henry's law constant, octanol-air partition coefficient and supercooled liquid vapor pressure of carbazole as a function of temperature: application to gas/particle partitioning in the atmosphere.

The Henry's law constant for carbazole was experimentally determined between 5 and 35 degrees C using a gas-stripping technique. The following equation was obtained for dimensionless Henry's law constant (H') versus temperature (T, K): ln H' = -3982(T,K)(-1) + 1.01. Temperature-dependent octanol-air partition coefficients (KOA) and supercooled liquid vapor pressures (PL,Pa) of carbazole were also determined using the GC retention time method. The temperature dependence of KOA and PL were explained by the following: log KOA = 4076/(T,K) - 5.65, log PL(Pa) = -3948(T,K)(- 1) + 11.48. The gas and particle-phase carbazole concentrations measured previously in Chicago, IL in 1995 was used for gas/particle partitioning modeling. Octanol based absorptive partitioning model consistently underpredicted the gas/particle partition coefficients (Kp) for all sampling periods. However, overall there was a good agreement between the measured Kp and soot-based model predictions.

Air↗
PubMed2006

Different retention behavior of structurally diverse basic and neutral drugs in immobilized artificial membrane and reversed-phase high performance liquid chromatography: comparison with octanol-water partitioning.

The retention behavior of 43 structurally diverse neutral and basic drugs in immobilized artificial membrane chromatography was investigated and compared to the reversed-phase retention and octanol-water partitioning. IAM chromatography was performed using morpholinepropanesulfonic acid (MOPS) or phosphate buffer saline (PBS) at pH 7.4 as the aqueous component of the mobile phase. The differences in the retention factors were attributed to increased electrostatic interactions in the MOPS environment, dependent on the fraction of charged species. Electrostatic interactions were found to play a key role in the relationships with reversed-phase retention factors determined under two different mobile phase conditions as well as in the relationships with lipophilicity data. IAM retention factors correlated better with octanol-water partition coefficients log P than with log D(7.4), as a result of the contribution of electrostatic forces in IAM retention. With log D(7.4) the relationships were improved when the fraction of charged species was taken into consideration. In any case the regression coefficient of log P or log D(7.4) was considerably lower than 1 reflecting the reduced hydrophobic environment of the IAM stationary phase. The different data sets were submitted to principal component analysis for further exploration of their similarities/dissimilarities.

Chromatography, High Pressure Liquid↗
PubMed2004

Crystal forms of tolbutamide from acetonitrile and 1-octanol: effect of solvent, humidity and compression pressure.

The possibility of obtaining tolbutamide polymorphs was investigated using the solvents acetonitrile and 1-octanol. Tolbutamide is an oral hypoglycemic agent that exists in four polymorphic forms. Characterization of the various polymorphs was carried out by differential scanning calorimetry (DSC), powder X-ray diffraction (PXRD), infrared spectroscopy (FTIR), optical microscopy and dissolution studies. Form A, crystallized from acetonitrile, resembled the form I polymorph, while form O, crystallized from 1-octanol, resembled the form III polymorph. Tablets of both form A and form O were produced at compression pressures of 2500 lbs and 5000 lbs using cornstarch and talc and were exposed to 40%, 75% and 95% RH conditions. DSC and PXRD studies did not show any significant drug-excipient interaction. Moreover, the change in the crystalline state of either form upon exposure to humidity was not evident. Dissolution studies showed a significantly lower drug release rate from form O tablets compressed at 5000 lbs pressure and exposed to 95% RH. Pressure and humidity had no significant effect on the dissolution profiles on the form A tablets. It was concluded that form A was the robust choice for further formulation development.

1-Octanol↗
PubMed2006

Application of the ion pair concept to the n-octanol-water partitioning of cefepime and cefpirome.

The ion pair concept was applied for the assessment of lipophilicity of cefepime and cefpirome. Octanol-water distribution coefficients were determined in presence of different concentrations [X-] of sodium octanesulphonate. The log Dx values within the linear part of the log Dx/[X-] relationships were extrapolated to log Do values corresponding to the partitioning in absence of the counter ion. Measurements were feasible at pH values close to the isoelectric points of the acidic and basic functions. In that pH range the conduction of the experiments in presence of the hydrophobic counter anion facilitated the partitioning of the two cephalosporins to octanol, circumventing the problems arising from their high hydrophilicity. This procedure could not be applied at lower pH, possibly due to a further drastic decrease in the 'intrinsic' lipophilicity or to reduced ion pairing potential of octanesulphonate, and at higher pH due to the disruption of the zwitterionic structure. Extrapolated log Do values were compared to actual log D measurements performed for a reference quinolinium compound and for cefpirome. Extrapolated retention factors log kw close to the isoelectric point were also determined by reversed phase HPLC and compared to the log Do values.

1-Octanol↗
PubMed2005

Retention of substituted coumarins using immobilized artificial membrane (IAM) chromatography: a comparative study with n-octanol partitioning and reversed-phase HPLC and TLC.

The chromatographic indices log k(wIAM) have been determined by HPLC on an immobilized artificial membrane column for a set of coumarin derivatives. The investigated compounds contain substituted amidoximes, or substituted heterocycles directly attached to the coumarinic skeleton. The log k(wIAM) values were compared to previously reported data of octanol-water partition coefficients and extrapolated capacity factors determined by reversed phase HPLC and TLC. The log k(wIAM) values of the investigated compounds were found to be comparable with the corresponding log P values, although they constitute a lower lipophilicity scale due to the reduced hydrophobic environment of the IAM stationary phase. These features were exemplified in their interrelationship with a slope close to unity and a large negative intercept. In contrast their comparison with the corresponding HPLC and RP-TLC capacity factors revealed differences in the retention mechanism reflected in slopes lower than unity, which were postulated to be due to secondary interactions under the reversed phase chromatographic conditions. However, conformational effects in the molecular structures of the coumarin derivatives were found to have a similar impact in their affinity for the IAM and octadecyl silane stationary phases, while they did not affect their octanol-water partitioning.

1-Octanol↗
PubMed2003

Applications of immobilised artificial membrane chromatography to quaternary alkylammonium sulfobetaines and comparison of chromatographic methods for estimating the octanol-water partition coefficient.

The chromatographic behaviour of a series of quaternary alkylammonium sulfobetaines of general formula RN-(CH3)2(CH2)nSO3-, where n = 2-4, has been examined using an immobilised artificial membrane column. The k values have been correlated both with experimentally determined values for the octanol-water partition coefficient (P) and with aquatic toxicity measurements. Other indirect chromatographic methods for measuring log P for these compounds using reversed-phase columns and octanol-coated columns have also been investigated.

Betaine↗
PubMed2001

Partial order ranking-based QSAr's: estimation of solubilities and octanol-water partitioning.

Partial order ranking appears as an attractive alternative to conventional Quantitative Structure Activity Relationships (QSAR) methods, the latter typically relying on the application of statistical methods. The method seems attractive as a priori knowledge of specific functional relationships is not required. In the present study, it is demonstrated that QSAR models based on a partial order ranking approach can be used satisfactorily to predict solubilities and octanol-water partitioning for a selection of organic compounds exhibiting different structural and electronic characteristics. The uncertainty is validated using well-established LSER descriptors. Two requirements to the model with regard to precision prevail, i.e., the model must be able to rank the single compounds in the basis set correctly compared to the experimental data, and the model should be based on a basis set of compounds large enough to secure a satisfactorily fine-meshed net, taking the number of descriptors into account. In the present study, the model was able to rank 318 out of 319 comparisons correctly in the case of solubilities. The corresponding figures for the octanol-water partitioning were 407 out of 408. The precision and the uncertainties of the method which, were found closely related to the mutual interplay between the number of compounds and the number of descriptors is discussed in terms of the number of descriptors and compounds involved. The limitations of the method are discussed.

Forecasting↗
PubMed2003

Quantitative predictive models for octanol-air partition coefficients of polybrominated diphenyl ethers at different temperatures.

Quantitative predictive models for octanol-air partition coefficients of polybrominated diphenyl ethers at different environmental temperatures (T) were developed. Partial least squares (PLS) regression was used for model development. A list of 18 theoretical molecular structural descriptors was screened by PLS analysis. The optimal model was selected from the one containing nine theoretical molecular descriptors and 1/T as predictor variables. The cross-validated Q(2)(cum) value for the optimal model is 0.975, indicating a good predictive ability and stability of the model. Intermolecular dispersive interactions play a leading role in governing the magnitude of logK(OA). The lower the E(LUMO) (the energy of the lowest unoccupied molecular orbital), the greater the intermolecular interactions between octanol and PCB molecules, and thus the greater the logK(OA) values.

Environmental Pollutants↗
PubMed2002

Protometric thermometric titrations of sparingly soluble compounds in water in the presence of n-octanol.

Thermometric titrimetry permits titration of acido-basic compounds in water in the presence of n-octanol. n-Octanol permits the solubilization of protolytes and moreover may also displace the equilibria of the titration reactions. Hydrochlorides of highly insoluble derivatives such as phenothiazine derivatives can be titrated with satisfactory accuracy and precision by sodium hydroxide despite their high pK(a) values. Likewise barbiturate salts can be titrated by hydrochloric acid. In the case of some salts, the methodology may permit the sequential titration of the ion and counter ion.

1-Octanol↗
PubMed2002

The effect of the nature of H-bonding groups on diffusion through PDMS membranes saturated with octanol and toluene.

The permeation of a series of structurally related compounds across silicone membranes (PDMS) was studied. The PDMS was saturated either with toluene, to mimic a functionally inert barrier, or octanol, to mimic the polar/hydrogen bonding environment of the stratum corneum lipid barrier. Phenol, salicylic acid, benzoic acid, anisole, phenylethanol and benzyl alcohol were chosen in an attempt to relate permeation to their different H-bonding capabilities. The flux was lower through the octanol system suggesting retardation by polar/H-bonding interactions. Separation of the permeability coefficient into its thermodynamic (partition coefficient) and kinetic (diffusion coefficient) terms suggests that the effect of altering polarity within the membrane has a greater impact on the diffusion of permeant rather than its chemical potential within the membrane.

Diffusion↗
PubMed1989

Correlation of partitioning of nitroimidazoles in the n-octanol/saline and liposome systems with pharmacokinetic parameters and quantitative structure-activity relationships (QSAR).

The partitioning of a series of nine nitroimidazole drugs in liposomes (log Km) of various compositions has been determined and compared to their partitioning in the n-octanol/saline system (log K) at 30 degrees C. The log Km ranged from 1.5 to 0.5 and was three- to fourfold greater than the log K; further, the linear correlation coefficient was greatest when cholesterol (CHOL)-free liposomes were used. Functional-group contributions were compared from their hydrophobic substituent constants and, except in the case of RO-07-2044 and iodoazomycin riboside, yielded negative values in all systems. Literature values of four pharmacokinetic parameters obtained in dogs and acute LD50 values of the nitroimidazoles in BALB/c mice were highly correlated with log K or log Km only in CHOL-free liposomes. Comparing the relative sensitizing effect of the nitroimidazoles in murine EMT-6 or Chinese hamster V79 tumor cell cultures and their partition coefficients, the correlation in EMT-6 cells was poor, whereas the correlation in V79 cells was greater than 0.9 when log Km was used but less than 0.6 when log K was used. Thus, the liposome model is a better predictor of nitroimidazole activity than the n-octanol/saline system and, also, it is a more flexible model for selecting the optimum conditions for QSAR studies.

Animals↗
PubMed2002

Molecular factors influencing retention on immobilized artifical membranes (IAM) compared to partitioning in liposomes and n-octanol.

PURPOSE: To assess the effect of molecular factors influencing retention on immobilized artificial membrane (IAM) high-performance liquid chromatography columns compared to liposomal partitioning and traditional n-octanol/water partition coefficients. METHODS: IAM capacity factors were measured at pH 7.0 on an IAM.PC.DD2 stationary phase. Liposomal partitioning at pH 7.0 and n-octanol/water partition coefficients were measured using the pH metric method. Partitioning in egg-phosphatidylcholine (PhC) liposomes was also measured by equilibrium dialysis for a series of beta-blockers. RESULTS: For the ionized beta-blockers, potentiometry and equilibrium dialysis yielded consistent partitioning data. For relatively large bases. IAM retention correlated well with PhC liposome partitioning, hydrophobic forces being mainly involved. For more hydrophilic compounds and for heterogeneous solutes, in contrast, the balance between electrostatic and hydrophobic interactions was not the same in the two systems. Hydrogen bonding, an important factor in liposomes partitioning, played only a minor role in IAM retention. CONCLUSIONS: Partitioning in immobilized artificial membranes depends on size, hydrophobicity, and charge. When hydrophobic interactions dominate retention, IAM capacity factors are well correlated with liposomal partitioning. On the contary, for hydrophilic solutes, the two systems do not yield the same information and are not interchangeable.

1-Octanol↗
PubMed2004

Lipase-catalyzed esterification of palm-based 9,10-dihydroxystearic acid and 1-octanol in hexane--a kinetic study.

The esterification of palm-based 9,10-dihydroxystearic acid (DHSA) and 1-octanol in hexane as catalyzed by lipase from Rhizomucor meihei (Lipozyme IM) followed Michaelis-Menten kinetics. The esterification reaction follows a Ping-Pong, Bi-Bi mechanism. The maximum rate was estimated to be 1 micromol min(-1) mg(-1) catalyst in hexane at 50 degrees C, and the Michaelis-Menten constants for DHSA and 1-octanol were 1.3 M and 0.7 M, respectively.

Catalysis↗
PubMed2003

pH dependence of the relative hydrophobicity and lipophilicity of amino acids and peptides measured by aqueous two-phase and octanol-buffer partitioning.

Partitioning of a series of free amino acids, their derivatives, and homo-oligopeptides in aqueous dextran-PEG two-phase systems and octanol buffer systems was examined at pH values from 2.0 up to 12.5. The pH-dependent partition behavior of free amino acids and peptides in the two-phase systems was compared with that of monofunctional drug-like compounds and found to be clearly different. The differences observed indicate that the information provided by the techniques of partitioning in octanol buffer (log(D)(pH)) and in aqueous two-phase systems, N(CH2), is different. It is suggested that the combination of the two descriptors, log(D) (lipophilicity) and N(CH2) (relative hydrophobicity), may be useful for QSAR analysis of the biological activities involving distribution and/or transport of chemical compounds in biological systems.

Amino Acids↗
PubMed2006

Physicochemical properties/descriptors governing the solubility and partitioning of chemicals in water-solvent-gas systems. Part 1. Partitioning between octanol and air.

QSPR analyses of a data set containing experimental partition coefficients in the three systems octanol-water, water-gas, and octanol-gas for 98 chemicals have shown that it is possible to calculate any partition coefficient in the system 'gas phase/octanol/water' by three different approaches: (1) from experimental partition coefficients obtained in the corresponding two other subsystems. However, in many cases these data may not be available. Therefore, a solution may be approached (2), a traditional QSPR analysis based on e.g. HYBOT descriptors (hydrogen bond acceptor and donor factors, SigmaCa and SigmaCd, together with polarisability alpha, a steric bulk effect descriptor) and supplemented with substructural indicator variables. (3) A very promising approach which is a combination of the similarity concept and QSPR based on HYBOT descriptors. In this approach observed partition coefficients of structurally nearest neighbours of a compound-of-interest are used. In addition, contributions arising from differences in alpha, SigmaCa, and SigmaCd values between the compound-of-interest and its nearest neighbour(s), respectively, are considered. In this investigation highly significant relationships were obtained by approaches (1) and (3) for the octanol/gas phase partition coefficient (log Log).

1-Octanol↗
PubMedDate not supplied

Rapid determination of partition coefficients between n-octanol/water for cardiovascular therapies.

The lipid solubility of a pharmaceutical may greatly influence its tissue activity. To evaluate lipid solubility of a group of cardiovascular agents a procedure to determine partition coefficients in n-octanol/water for a series of cardiovascular compounds was described. Ultraviolet absorbance measurements were used to assess partitioning between the two liquid phases of these compounds. In this study, sotalol was found to be the most hydrophilic (n-octanol/water ratio of 0.33) and fosinopril-sodium was the most lipophilic (ratio of 6.19). This is a versatile method permitting the evaluation of lipophilicity and, thus, parameters governing the events leading to pharmacologic actions such as gastrointestinal dissolution, absorption, and bioavailability. These observations can be related to a drug series, composed of several compounds having structural similarities or minor variations. The lipid solubility of a compound can markedly alter its side-effects profile, especially because lipophilic drugs enter the central nervous system with facility. Additionally, lipophilic agents may enter target tissue with greater ease than nonlipophilic compounds and thus possess local intracellular effects in addition to a macro systemic action.

1-Octanol↗