Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Octanols”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 163 records · Page 9Linked to original sources
PubMed1998

Rapid estimation of octanol-water partition coefficients of pesticides by micellar electrokinetic chromatography.

Micellar electrokinetic chromatography (MEKC) was evaluated as a new technique for the rapid estimation of octanol-water partition coefficient (logKow). Retention measurements for more than 40 reference pesticides with varied structural characteristics and hydrophobicity were carried out in two MEKC systems, based on sodium dodecyl sulfate (SDS) and sodium cholate (SC), respectively. To enable an accurate determination of capacity factors in the SC-MEKC system, cypermethrin (a synthetic pyrethroid insecticide) was utilized instead of Sudan III as the SC micelle tracer, since a few highly hydrophobic pesticides were found to elute after Sudan III. The linear correlation between logarithmic capacity factor (logk') and logKow in the two systems was examined. It was found that, under the typical buffer condition (10 mM sodium phosphate with 60 mM surfactant, pH 7.0), the SDS-MEKC system provided a somewhat wider dynamic range for hydrophobicity (logKow from -1.0 to 4.5). However, the correlation of logk' with logKow was not very high when all the reference pesticides were included in one single calibration set. For the SC-MEKC system, the dynamic range for logKow was in the range of 1.0-5.5, and a good linear correlation existed between logk' and logKow, even when all reference pesticides were incorporated into a single calibration group. By comparing the regression line of the reference pesticides with that of a group of simple aromatic derivatives, it was discovered that molecular size and functionality posed a less significant effect on the measurement of logKow in the SC-MEKC system than in the SDS-MEKC system. Thus, SC-MEKC shall be the system of choice for the estimation of logKow. The typical error on logKow determination using the current MEKC technique was within 0.5 units, suggesting that MEKC can be a valuable complement to reversed phase high performance liquid chromatography (RP-HPLC) for the indirect determination of logKow. Besides maintaining all the advantages of the HPLC approach, the MEKC technique showed some unique benefits, such as better inter-column reproducibility, higher throughput, and less handling of toxic pesticides and solvents.

Chromatography↗
PubMed1977

Solvent-dependent conformational system of hydroxyureas in octanol-water and in inhibition of ribonucleotide reductase.

The carbonyl nitrogen IR absorption region of selected hydroxyureas was examined in octanol. The spectra indicated appreciably different absorptions prior to and after equilibration with water. Stability studies on the hydroxyureas indicated that the absorption differences were not due to chemical decomposition in the equilibration process but were due to solvent conformation and/or tautomeric dependency of the system. Preliminary in vitro inhibition of the enzyme ribonucleoside diphosphate reductase by selected hydroxyureas also indicated an apparent solvent dependency, which may involve the conformational and/or tautomeric properties of these agents. The implications of the solvent-dependent conformation-tautomeric system observed are discussed in relation to this property in the biological action of these agents.

Chemical Phenomena↗
PubMed1985

Solubility properties in polymers and biological media 5: an analysis of the physicochemical properties which influence octanol-water partition coefficients of aliphatic and aromatic solutes.

Octanol-water partition coefficients of 102 aliphatic, polychloro aliphatic, and aromatic non-hydrogen-bond donor and hydrogen-bond donor solutes are well correlated (r = 0.989, SD = 0.175) by the equation: log Kow = 0.20 + 2.74 V/100 - 0.92 pi - 3.49 beta, where V is the molar volume (taken as the molecular weight divided by the liquid density) and pi and beta are the solvatochromic parameters that measure solute dipolarity/polarizability and hydrogen-bond acceptor basicity. A set of "ground rules" (modifications of the input parameters) are described which allow the inclusion of both aliphatic and aromatic solutes in the same correlation equation. Monomer beta values (betam) are used for alcohol solutes.

Chemical Phenomena↗
PubMed1987

Some advantages of calculating octanol-water partition coefficients.

Reliable values for the octanol-water partition coefficients of small solutes used in enzyme binding/inhibition studies are desirable if a hydrophobic effect is being examined. Many investigators will grant that measuring each solute by shake-flask is the ideal, but reversed-phase HPLC data is becoming more commonplace since it is easier to obtain. This note examines one study where HPLC hydrophobicity, from an apparently valid procedure, obscured an obvious hydrophobic relationship. Another example is cited where probable errors in shake-flask measurement also lead to an erroneous conclusion. In both instances, values obtained from a simple method of calculation of log P(o/w) values could have provided a warning.

Chromatography, High Pressure Liquid↗
PubMed1995

Atom/fragment contribution method for estimating octanol-water partition coefficients.

Atom/fragment contribution values, used to estimate the log octanol-water partition coefficient (log P) of organic compounds, have been determined for 130 simple chemical substructures by a multiple linear regression of 1120 compounds with measured log P values. An additional 1231 compounds were used to determine 235 "correction factors" for various substructure orientations. The log P of a compound is estimated by simply summing all atom/fragment contribution values and correction factors occurring in a chemical structure. For the 2351 compound training set, the correlation coefficient (r2) for the estimated vs measured log P values is 0.98 with a standard deviation (SD) of 0.22 and an absolute mean error (ME) of 0.16 log units. This atom/fragment contribution (AFC) method was then tested on a separate validation set of 6055 measured log P values that were not used to derive the methodology and yielded an r2 of 0.943, an SD of 0.408, and an ME of 0.31. The method is able to predict log P within +/- 0.8 log units for over 96% of the experimental dataset of 8406 compounds. Because of the simple atom/fragment methodology, "missing fragments" (a problem encountered in other methods) do not occur in the AFC method. Statistically, it is superior to other comprehensive estimation methods.

Chemical Phenomena↗
PubMed2005

High-resolution gas chromatography retention data as a basis for estimation of the octanol-water distribution coefficients (Kow) of PCB: the effect of experimental conditions.

The semi-experimental approach to approximating physicochemical data relevant to environmental distribution (vapor pressure and gas-octanol distribution) by correlation with gas chromatography (GC) retention data has been extended to the determination of Kow values. We estimated Kow values >10(4) for polychlorinated biphenyls (PCB), which are often derived by liquid chromatography, by correlation with gas chromatographic retention data. Selecting a set of reference compounds with known Kow values for relative retention time (RRT) correlation enables easy and accurate semi-empirical calculation of further Kow values for a given group of congeners. The RRT/log Kow correlation is validated in this paper with regard to the following gas chromatographic conditions: (1) isothermal versus temperature-programmed elution, (2) the possible effect of the polarity of the stationary phase, and (3) the effect of the format of the standardized GC retention data. The advantages of our Kow(GC) method can be summarized as follows: complex mixtures can be analyzed, only amounts in the nanogram-range or less are required, Kow values of isomers can be determined and the exact structure of compounds need not be known. Normalized GC retention data of persistent organic pollutants are readily available. The quality of the Kow values obtained by the GC method compares well with that for other Kow estimation methods. It depends mainly on the accuracy of the Kow data of the structurally correlated compounds used as standards for the correlation cohort. The Kow(GC) data for all 209 PCB congeners are given.

Chemical Phenomena↗
PubMed2005

Production of the long-chain alcohols octanol, decanol, and dodecanol by Escherichia coli.

As a follow-up to earlier studies on the emission of long-chain alcohols from broth cultures of Gram-negative enteric bacteria, E. coli was examined for the production of 1-octanol, 1-decanol, and 1-dodecanol. Ten strains of E. coli cultured in tryptic soy broth were assayed for volatile metabolites using solid-phase microextraction. Long-chain alcohols were produced by all strains with 1-decanol predominating with production ranging from 23.6 ng mL(-1) to 148 ng mL(-1). The production of long-chain alcohols followed the onset of the exponential growth phase of the broth culture. Doubling the concentration of glucose (5 g L(-1)) in the broth had no effect on the concentration of long-chain alcohols produced. Addition of octanoic, decanoic, or dodecanoic acids (as K(+) salts) to the broth (100 mg L(-1)) markedly increased the production of the corresponding alcohols by E. coli, ranging from a 13-fold increase for decanol to a 51-fold increase for dodecanol. However, decanol remained the predominant alcohol detected in all assays. These neutral volatile alcohols may have application as vapor-phase indicators for certain classes of bacteria, particularly, Gram-negative enteric bacteria.

Chromatography, Gas↗
PubMed1995

Modelling non-equilibrium concentrations of microcontaminants in organisms: comparative kinetics as a function of species size and octanol-water partitioning.

From our experience, risk assessment for environmental management and research purposes is in need of models that apply to many of the species we want to protect from many of the microcontaminants released. The traditional one-compartment model serves as such a tool during interpretation and extrapolation of information on concentration kinetics. Unfortunately, its non-steady parameters are specific for a combination of a compound and a species. So, one must seriously face the prospect that their values will never be measured for most compounds and species due to experimental, ethical and financial constraints. It was therefore considered worthwhile to relate the main non-steady state parameter, viz. the outflow (elimination, clearance, depuration) rate, to common characteristics of compounds and species. The outflow rate (kout) for persistent organic microcontaminants was correlated to the octanol-water partition ratio of the compound (Kow) and the size of the species (z). The regressions for aquatic invertebrates, fish and warm-blooded animals were kout = (1/(4*10(-3)*Kow + 7*10(-8)) + 5*10(-3))*z-0.36 (n = 53, r2 = 0.45), kout = (1/(4*10(-4)*Kow + 5) + 4*10(-3))*z-0.19 (n = 140, r2 = 0.68) and kout = (1/(3*10(-4)*Kow + 2*10(-5)) + 8*10(-3))* z-0.86 (n = 51, r2 = 0.48) respectively. The correlation was less strong if Kow or z were omitted. In addition to the minimum loss rate for persistent compounds, one may distinguish an excess outflow rate (mainly caused by biotransformation) for less persistent organic microcontaminants. The order of magnitude difference is explored and ways to refine these estimations are discussed briefly. Outflow rates for cadmium and mercury are linked to species size with the same type of function. The internal consistency of the model was verified by calculating inflow rates from calibrated outflow rates and comparing these to independent measurements. Moreover, the constants in the regressions are explained physically and their value is compared with those obtained in ecology for consumption, production and respiration. The exponent that scales these rates to the species size is similar to the regressions for outflow rates obtained here. The model allows estimations for fairly unknown substances or species and it is thought to help refining risk evaluations without extensive experimental or desk studies. As this paper shows that joint application of chemical (Kow) and ecological (z) information yields more accurate estimations, this study contributes to the often advocated integration of both disciplines in ecotoxicology.

Animals↗
PubMed1986

Octanol:water partition coefficients (P): measurement, estimation, and interpretation, particularly for chemicals with P greater than 10(5).

Methods for measurement and estimation of octanol:water partition coefficients are discussed with particular reference to high values (log P greater than 5). A novel experimental method for P measurement is described and preliminary results presented. The use of high performance liquid chromatography capacity factors for estimating P values has been investigated; better correlations between the two parameters have been found if HPLC results at different methanol:water liquid phases are extrapolated to pure water, but even this procedure does not always give reliable P values. The interpretation of high log P values in terms of fish bioconcentration is discussed and the correlations of molecular connectivity and molecular weight with fish bioconcentration are presented.

Animals↗
PubMed2005

QSPR models for polychlorinated biphenyls: n-Octanol/water partition coefficient.

The logarithmic n-octanol/water partition coefficient (logK(ow)) is an important property for pharmacology, toxicology and medicinal chemistry. Quantitative structure-property relationship (QSPR) model for the lipophilic behaviour (logK(ow)) of the data set containing 133 polychlorinated biphenyl (PCB) congeners is analyzed using the conceptual density functional theory based global reactivity parameter such as electrophilicity index (omega) along with energy of lowest unoccupied molecular orbital (E(LUMO)) and number of chlorine substituents (N(Cl)) as descriptors. A reasonably good coefficient of determination (r(2) = 0.914) and the internal predictive ability (r(cv)(2) = 0.909) values are obtained indicating the significance of the considered descriptors in the property analysis of PCBs. Further, the developed method has widespread applicability from chemical reactivity to toxicity analysis and in studies related to various physicochemical properties in the series of dioxins and other polyaromatic hydrocarbons.

Models, Chemical↗
PubMed2004

A neural network based prediction of octanol-water partition coefficients using atomic5 fragmental descriptors.

An artificial neural network based approach using Atomic5 fragmental descriptors has been developed to predict the octanol-water partition coefficient (logP). We used a pre-selected set of organic molecules from PHYSPROP database as training and test sets for a feedforward neural network. Results demonstrate the superiority of our non-linear model over the traditional linear method.

Models, Chemical↗
PubMed2005

Octanol-water partition coefficient of glucose, sucrose, and trehalose.

The octanol-water partition coefficients (P) of glucose, sucrose, and trehalose were measured at temperatures between 5 and 20 degrees C using an enzymatic method. The measured log P is compared with calculated and experimental data previously reported. In the case of trehalose, the measured log P differs considerably from the theoretically estimated values and agrees with the expected value for a disaccharide. Some methods of assessing the partition coefficients are also analyzed and it is concluded that the atom/fragment contribution method overestimates the hydrophilicity of disaccharides and, probably in a larger extension, that of trisaccharides. The knowledge of P for these sugars is valuable both for basic or applied purposes, including food and biomolecules stabilization.

1-Octanol↗
PubMed2005

Prediction of octanol--air partition coefficients of semivolatile organic compounds based on molecular connectivity index.

A new method has been developed to describe the quantitative relationship between the octanol-air partition coefficients and molecular connectivity indexes of semivolatile organic compounds such as polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), polychlorinated naphthalenes (PCNs), polycyclic aromatic hydrocarbons (PAHs), chlorobenzenes (CBs), polybrominated diphenyl ethers (PBDEs). The stepwise multiple linear regression was used to derive six equations with correlation coefficients greater than 0.99 except for PBDEs' (0.96). The largest relative error is 4.6%, and the standard deviation is less than 1.83 log units. Compared with the data obtained from the relevant experiments, the results of prediction are very accurate.

Air↗
PubMed2006

Determination of n-octanol/water partition and membrane binding of cationic porphyrins.

Porphyrin and their derivatives are being systematically studied as photosensitizers for photodynamic therapy. The ability to predict their membrane partition properties is of key importance to unveil their in vivo activity and applications. Several n-octanol/water partition coefficients (logP(OW)) of porphyrin derivatives have been reported in the literature but large discrepancies have been observed. Reproducible and reliable logP(OW) data for a series of 20 cationic meso-phenyl(pyridyl)porphyrin derivatives were determined by correlating logP(OW) with the partition coefficients measured in a more adequate n-butanol/water system. Linear correlations as a function of the number of positively charged groups bound to the periphery of the porphyrin rings were found within each series. A significant effect of the stereochemistry and nature of the positively charged substituents was also observed, but diminished steadily converging to a similar value in the mono-substituted derivatives. Binding constants to liposomes were shown to be proportional to logP(OW), except for the cis-isomers of doubly charged porphyrins. The cis-isomer presented smaller logP(OW) and higher membrane affinity. The effect was explained based on the amphiphilic nature of the cis-porphyrin.

1-Octanol↗
PubMed2005

Octanol-water partitioning of chemical constituents in river water and treated sewage effluent.

A shake-flask approach has been employed to determine the n-octanol-water partitioning of chemical constituents in various river waters and in treated sewage effluent. The bulk inorganic composition of the water samples (conductivity, pH and the concentrations of major solutes: Ca, K, Mg, Na) was unaffected by the presence of solvent. Boron, however, exhibited increasing partition with decreasing sample pH, because its dominant form in freshwaters, B(OH)3, is neutral, covalent and acidic. Constituents having significant association with dissolved organic matter (DOM), including components of DOM itself (C, S) and trace metals that form complexes with organic ligands (Al, Cu, Fe, Pb, Zn), exhibited measurable partition into the solvent in most cases, with conditional partition coefficients, D(ow), in the region 0.03-2.5. Significant differences in the partitioning among these constituents and among the environments studied did not appear to be related to bulk sample characteristics or the degree of association of the constituent with DOM. These observations suggest that partition is sensitive to the nature of the organic matter (C, S) and the availability of specific binding ligands (trace metals). Thus, although D(ow) is critical for defining the biogeochemical behaviour and potential impacts of chemical constituents in the environment, it appears to be a difficult parameter to model or predict.

1-Octanol↗
PubMed2001

Determination of octanol-water partition coefficients of pesticides by microemulsion electrokinetic chromatography.

Microemulsion electrokinetic chromatography (MEEKC) was evaluated as a screening tool for the indirect measurement of octanol-water partition coefficients (log Po/w) of pesticide compounds. Over 80 pesticide compounds representing a variety of structural characteristics were studied, and good correlation of log Po/w with the logarithm of the retention factor was found. The microemulsion system studied allowed the separation of compounds in the log Po/w range of -1 to 7. In addition, a smaller set of simple organic molecules that vary in structural features was evaluated and compared to the pesticide log Po/w calibration. The pesticide and simple organic molecule log Po/w calibration lines were statistically similar. This suggests that a universal set of standard compounds may be employed for the log Po/w calibration to provide measurements for a variety of compounds with good accuracy.

Calibration↗