Ow Values Research Articles

Estimation of n-octanol/water partition coefficients of polycyclic aromatic hydrocarbons by quantum chemical descriptors

Abstract Quantitative structure-property relationship (QSPR) modeling is a powerful approach for predicting environmental behavior of organic pollutants with their structure descriptors. This study reports an optimal QSPR model for estimating logarithmic n-octanol/water partition coefficients (log K OW) of polycyclic aromatic hydrocarbons (PAHs). Quantum chemical descriptors computed with density functional theory at B3LYP/6-31G(d) level and partial least squares (PLS) analysis with optimizing procedure were used for generating QSPR models for log K OW of PAHs. The squared correlation coefficient (R 2) of the optimal model was 0.990, and the results of crossvalidation test (Q 2cum=0.976) showed this optimal model had high fitting precision and good predictability. The log K OW values predicted by the optimal model are very close to those observed. The PLS analysis indicated that PAHs with larger electronic spatial extent and lower total energy values tend to be more hydrophobic and lipophilic.

Improvement of microemulsion electrokinetic chromatography for measuring octanol–water partition coefficients

Microemulsion electrokinetic chromatography (MEEKC) has been used to indirectly measure octanol-water partition coefficients (log P(ow)) of compounds. In order to obtain an accurate log P(ow) value, the electrophoretic mobilities of the microemulsion phase (mu(me)) and the analyte (mu(eff)) in MEEKC must be accurately required. However, in conventional MEEKC, the shortage of obtaining mu(me) with a tracing method was discovered, and the influences of concentration, injection volume of analyte, and high electric field on measuring mu(eff) were also found. In this paper, a novel method called improved MEEKC (I-MEEKC) was developed to avoid the problems mentioned above. In I-MEEKC, a nonlinearity fitting program was used to obtain mu(me) to avoid the error from tracing mu(me); the extrapolating method was used to eliminate the effects of concentrations and injection volumes of analytes on mu(eff) measurement, and an enough stable microemulsion was selected to eliminate the effect of high electric field on mu(eff )measurement. Then the novel method was applied to estimate log P(ow) of uncharged compounds and charged pharmaceuticals compared to the conventional MEEKC. The log P(ow) of all analytes obtained by I-MEEKC agreed with those obtained by classical shake flask or literature values, the errors between them were within 0.1 logarithm units, better than the ones by conventional MEEKC.

QSAR Models for Predicting in Vivo Aquatic Toxicity of Chlorinated Alkanes to Fish

Quantitative structure-activity relationship (QSAR) models are expected to play a crucial role in reducing the number of animals to be used for toxicity testing resulting from the adoption of the new European Union chemical control system called Registration, Evaluation, and Authorization of Chemicals (REACH). The objective of the present study was to generate in vitro acute toxicity data that could be used to develop a QSAR model to describe acute in vivo toxicity of chlorinated alkanes. Cytotoxicity of a series of chlorinated alkanes to Chinese hamster ovary (CHO) cells was observed at concentrations similar to those that have been shown previously to be toxic to fish. Strong correlations exist between the acute in vitro toxicity of the chlorinated alkanes and (i) hydrophobicity [modeled by the calculated log K ow (octanol-water partition coefficient); r (2) = 0.883 and r int (2) = 0.854] and (ii) in vivo acute toxicity to fish ( r (2) = 0.758). A QSAR model has been developed to predict in vivo acute toxicity to fish, based on the in vitro data and even on in silico log K ow data only. The developed QSAR model is applicable to chlorinated alkanes with up to 10 carbon atoms, up to eight chlorine atoms, and log K ow values lying within the range from 1.71 to 5.70. Out of the 100204 compounds on the European Inventory of Existing Chemicals (EINECS), our QSAR model covers 77 (0.1%) of them. Our findings demonstrate that in vitro experiments and even in silico calculations can replace animal experiments in the prediction of the acute toxicity of chlorinated alkanes.

Ecotoxicological evaluation of polycyclic aromatic hydrocarbons using marine invertebrate embryo–larval bioassays

The toxicity of polycyclic aromatic hydrocarbons (PAHs) was determined using mussel, sea-urchin and ascidian embryo–larval bioassays. Fluorescent light exposure enhanced phenanthrene, fluoranthene, pyrene and hydroxypyrene toxicity in comparison with dark conditions, but not naphthalene and fluorene toxicity. The toxicity of PAHs was inversely related to their K OW values following QSAR models derived for baseline toxicity of general narcotics, whereas the obtained regression using toxicity data from photoactivated PAHs significantly departed from the general narcosis model. Also, the mixture toxicity of five PAHs to the larval growth of the sea-urchin was compared with predictions derived from the concentration addition concept, indicating less than additive effects. Finally, we compared our toxicity data with worst-case environmental concentrations in order to provide a preliminary estimate of the risk to the marine environment. Naphthalene, fluorene and pyrene are not considered to pose a risk to sea-urchin, mussel or ascidian larvae, whilst phenanthrene and fluoranthene may pose a risk for mussel and sea-urchin. Moreover, a higher risk for those species is expected when we consider the photoactivation of the PAHs.

The characterization of PCDDs, PCDFs and coplanar PCBs during the past 50 years in Gwangyang Bay, South Korea

The PCDD/DFs and coplanar PCBs (co-PCBs) in sediment samples from Gwangyang Bay in South Korea was investigated. The total concentration of dioxins and their toxic equivalent quantity (TEQ; calculated with the WHO 2005 Toxic Equivalency Factors) value in the surface sediment of the outer site (261 pg g −1 TOC, 4.4 pg-TEQ g −1) were 3-fold higher than the inner site (90 pg g −1 TOC, 1.1 pg-TEQ g −1) in the Bay. The dioxin in the sediment samples was found to come from a mixture of the impurities of pentachlorophenol (PCP), chloronitrofen (CNP) and combustion based on the result of hierarchical cluster analysis (HCA). These dioxin sources have been influenced by the characterization associated with this region which was both an agricultural-centered and industrial-centered area. According to principal component analysis (PCA) related to the K ow values for the congener-specific composition of co-PCBs in the sediment core, the Kanechlor (KC)-500 and the atmospheric deposition were identified as the possible sources. The maximum burden in the sediment core was 1.3 kg for 1967–1974 and the total burdens of PCDD/DFs and co-PCBs in the sediment core were estimated to be 6.6 kg during the past 50 years. The cumulative burdens of dioxin are still increasing in Gwangyang Bay.

PAHs in background soils from Western Europe: Influence of atmospheric deposition and soil organic matter

The levels and distribution of polynuclear aromatic hydrocarbons (PAHs) were determined in soil samples from background locations in the UK and Norway, to investigate their spatial distribution and the controlling environmental factors. Concentrations ranged between 42 and 11 200 μg kg −1 (geometric mean 640 μg kg −1) and 8.6 and 1050 μg kg −1 (150 μg kg −1) dry weight in the UK and Norwegian soil, respectively. Proximity to sources and locations susceptible to high atmospheric depositional inputs resulted in higher concentrations. Statistically significant relationships were observed between PAH and total organic carbon (TOC) in the Norwegian samples. High molecular weight PAHs correlated with black carbon (BC) in UK-woodland soil. These observations support the hypothesis that TOC plays an important role in the retention of PAHs in soil and that PAHs are often combined with BC during combustion emissions. PAHs with 4 and more rings comprised ∼90% of total PAHs in the UK soil, but only 50% in the Norwegian soil. The mixture of PAHs implied that fractionation occurred during long-range atmospheric transport and deposition. The lighter PAHs with lower K ow values more readily reached the most remote sites. The heavier PAHs with higher K ow values remained in closer proximity to sources.

Decline of pesticide residues from barley to malt

The fate of dinitroaniline herbicides (pendimethalin and trifluralin), organophosphous insecticides (fenitrothion and malathion), and pyrimidine (nuarimol) and triazole (myclobutanil and propiconazole) fungicides from barley to malt was determined. Several samples for residue analysis were taken after each stage of malting (steeping, germination and kilning). Pesticide residue analysis was carried out by GC/ITMS in selected ion monitoring mode. Pesticides decline along the process, although in different proportions. The carryover of residues after steeping was 45–85%. A good correlation (r > 0.92) was observed between percentages removed after steeping and the P OW values of pesticides. The amount remaining after malting ranged from 13 to 51% for fenitrothion and nuarimol, respectively. Steeping was the most important stage in the removal of pesticide residues (52%) followed by germination (25%), and kilning (drying and curing, 23%). During malt storage (3 months) the fall in pesticide residues was not significant. Applying the standard first-order kinetics equation (r > 0.95), the half-lives obtained for the pesticides during malt storage varied from 244 to 1533 days for myclobutanil and nuarimol, respectively.

Life cycle responses of the midge Chironomus riparius to polycyclic aromatic compound exposure

During acute exposure, polycyclic aromatic compounds (PACs) act mainly by narcosis, but during chronic exposure the same compounds may exert sublethal life cycle effects. The aim of this study was therefore to evaluate the chronic effects of sediment spiked PACs on the emergence of the midge Chironomus riparius. Three isomer pairs were selected, and 28-day LC 50 values and 50% emergence times (EMt 50) were determined. Concentration–response relationships were observed for phenanthrene, acridine, phenanthridine and acridone. Anthracene and phenanthridone had no effect on total emergence, but did cause a delay in emergence. Calculated porewater LC 50 values correlated well with log K ow values, suggesting narcosis as mode of action. In contrast, effect concentrations for delay in emergence (EMt 50) deviated from narcosis, suggesting a specific mode of action during chronic exposure. It is concluded that emergence is a powerful endpoint to detect life cycle effects of PACs on a key sediment inhabiting invertebrate.

Estimation of Water Sampling Rates and Concentrations of PAHs in a Municipal Sewage Treatment Plant Using SPMDs with Performance Reference Compounds

Semipermeable membrane devices (SPMDs) were exposed at ten sampling points, each representing a different stage in the treatment process, in a municipal sewage treatment plant. Differences in SPMD uptake kinetics of polycyclic aromatic hydrocarbons (PAHs) due to variations in conditions at the sampling sites were evaluated by using five performance reference compounds (PRCs) with log K(ow) values of 4.20 to 6.34. PRC release rate constants (k(e,PRC) values) were calculated for PRCs for which 50-98% of the initial amounts were lost during the sampling period. The k(e,PRC) values were high, ranging from 0.08 to 0.11 day(-1) for the studied PRCs, at sampling site W1 (raw sewage), the only sampling site where significant amounts of the PRCs with log K(ow) values > 5 were released from the SPMDs. At the other sampling sites, only PRCs with log K(ow) values between 4.20 and 4.50 were released in significant amounts. The release rates at these sites were lowest (0.04 day(-1)) at sampling site W9 (the secondary clarifier) and highest (0.18 day(-1)) at W8 (the active sludge aeration basin). Differences between sampling rates (R(s)) obtained using published laboratory-calibrated data and PRC-corrected R(s) values were visualized by principal component analysis (PCA). The water concentrations of 24 studied PAHs fell substantially during the course of the sewage treatment process. However, low molecular weight PAHs were more effectively removed than high molecular weight PAHs. Significant deviations between actual and estimated water concentrations may arise unless PRC-corrected R(s) values are applied.

Uptake of pesticides from water by curly waterweed Lagarosiphon major and lesser duckweed Lemna minor

The uptake of pesticides from water by two aquatic plants, the submersed Lagarosiphon major (Ridley) Moss and the floating duckweed Lemna minor L., was measured over periods of up to 72 h. Twelve non-ionised pesticides and analogues, chosen to span a wide range of physicochemical properties, and one analogue (3,5-D) of the phenoxyacetic acid herbicide 2,4-D were studied. Concentrations of the parent compound were determined in the plants following extraction and separation by chromatography. Quantification was by liquid scintillation counting for the (14)C-labelled compounds and by high-performance liquid chromatography for the four non-radiolabelled commercial pesticides. Uptake for all compound and plant combinations had reached equilibrium by 24 h. Accumulation of compound in the plant could be described well for most non-ionised compounds by equilibration into the aqueous phase in the plant cells together with partitioning onto the plant solids, this latter process becoming dominant in Lagarosiphon for compounds with log K(ow) > 1 and in Lemna for compounds with log K(ow) > 1.8. Lipophilic compounds with log K(ow) > 4 were concentrated more than 100-fold on a fresh-weight basis. However, the uptake of isoproturon and chlorotoluron was up to threefold less than expected from their K(ow) values, and their behaviour was better explained using solvation descriptors. Uptake of the acid 3,5-D was dependent on solution pH, this compound being strongly taken up at lower pH by the process of ion trapping, as previously observed in barley roots. Aquatic vegetation can thus rapidly accumulate pesticides, and could be an important sink especially for lipophilic pesticides reaching well-vegetated waters.

QSPR prediction of n-octanol/water partition coefficient for polychlorinated biphenyls

The logarithmic n-octanol/water partition coefficient (log K ow) is a very important property which concerns water-solubility, bioconcentration factor, toxicity and soil absorption coefficient of organic compounds. Quantitative structure–property relationship (QSPR) model for log K ow of 133 polychlorinated biphenyls (PCBs) is analyzed using heuristic method (HM) implemented in CODESSA. In order to indicate the influence of different molecular descriptors on log K ow values and well understand the important structural factors affecting the experimental values, three multivariable linear models derived from three groups of different molecular descriptors were built. Moreover, each molecular descriptor in these models was discussed to well understand the relationship between molecular structures and their log K ow values. The proposed models gave the following results: the square of correlation coefficient, R 2, for the models with one, two and three molecular descriptors was 0.8854, 0.9239 and 0.9285, respectively.

Salting-in and salting-out effects of ionic and neutral osmotica on limonene and linalool Henry’s law constants and octanol/water partition coefficients

Foliar emission rates of plant-generated volatile monoterpenes depend on monoterpene partitioning between air, aqueous and lipid-phases in the leaves. While Henry’s law constants ( H pc, equilibrium gas/water partition coefficient) and octanol/water partition coefficients ( K OW) for pure water have been previously used to simulate monoterpene emissions from the leaves, aqueous phase in plants is a complex solution of electrolytes and neutral osmotica. We studied the effects of dissociated compounds KCl and glycine and sugars glucose, sorbitol and sucrose with concentrations between 0 and 1 M on H pc and K OW values for limonene and linalool. Linalool with ca. 1500-fold lower H pc (2.62 Pa m 3 mol −1 for pure water at 30 °C) and ca. 30-fold lower K OW (955 mol mol −1 for pure water at 25 °C) is the more hydrophilic compound of the two monoterpenes. H pc of both monoterpenes increased with increasing concentration of both ionic compounds and sorbitol, but decreased with increasing glucose and sucrose concentrations. The salting-out coefficients for H pc ( k H) were ca. an order of magnitude larger for more hydrophilic compound linalool than for more hydrophobic limonene. For linalool, co-solutes modified H pc by 30–50% at the highest concentration (1 M) tested. The effect of temperature on the salting-out coefficient of KCl was minor. As with H pc, K OW increased with increasing the concentration of KCl, glycine and sorbitol, and decreased with increasing glucose and sucrose concentrations. For limonene, co-solutes modified K OW by 20–50% at the highest concentration used. For linalool, the corresponding range was 10–35%. Salting-out coefficients for H pc and K OW were correlated, but the lipid–solubility was more strongly affected than aqueous solubility in the case of limonene. Overall, these data demonstrate physiologically important effects of co-solutes on H pc and K OW for hydrophilic monoterpenes and on K OW for hydrophobic monoterpenes that should be included in current emission models.

Partitioning characteristics of PAHs between sediment and water in a shallow lake

Distribution of hydrophobic organic contaminants in abiotic compartments is essential for describing their transfer and fate in aquatic ecosystems. Taihu Lake is the third largest freshwater lake in China. Water quality of Taihu Lake has deteriorated greatly during the last decades and has threatened the water supply. The aim of the present study was to investigate the partitioning of polycyclic aromatic hydrocarbons (PAHs) among overlying water, suspended particulate matter (SPM), sediments, and pore water in Meiliang Bay, Taihu Lake and to provide useful information for the ecological engineering in this area. Overlying water and surface sediment were sampled from six sites in Meiliang Bay, Taihu Lake, China. Within 72 h of sampling, sediments were centrifuged to obtain the pore water. Overlying water samples were filtered to separate dissolved and SPM samples. After extraction, samples were purified following a clean-up procedure. PAH fraction was obtained by elution with a mixture of hexane: DCM (7:3, V/V) and analyzed by GC/MS. PAHs concentrations in overlying water varied from 37.5 ng/L to 183.5 ng/L. Concentrations of PAHs in pore water were higher than those in overlying water. The total concentrations of 16 priority PAHs in sediments ranged from 2091.8 ng/g-dw to 4094.4 ng/g-dw. PAHs concentrations on SPM were decreased with suspended solid concentrations (SSC). Total PAHs concentrations on SPM varied in the range of 3369.6 ng/g-dw to 7531.1 ng/g-dw. The partition coefficients between sediment and overlying water (log K oc) for PAHs with log K ow<5 were positively correlated with their octanol-water partition coefficients (log K ow) (n=39, r=0.79, p<0.0001). Partition coefficients between sediment and pore water (log K oc′) for all PAHs were also significantly correlated with their log K ow values (n=48, r=0.82, p<0.0001). In general, PAHs derived from combustion sources tend to bind strongly to soot particles in natural sediment. Consequentially, K oc values observed in the natural environment could be orders of magnitude higher than those predicted by linear correlation relationships under laboratory conditions. In the present study, the ratio of log K oc values to log K ow values falls consistently above 1, indicating that the sediment soot carbon in the bay was more attractive for PAHs than n-octanol. The log K oc′ was also higher than that predicted under laboratory conditions, suggesting that the measured pore water PAH concentrations were lower than those predicted. That is to say, not all the sediment PAHs can be available to partition rapidly into sediment pore waters. A variation in soot content is a possible reason. Furthermore, concentrations of PAHs on SPM were higher than those in sediments. The compositions of PAHs on SPM and in sediments were similar, indicating the importance of re-suspension process of sediments in the partitioning process of the shallow lake. The results indicated the equilibrium partitioning model could be used to predict PAHs distribution in various phases of a shallow lake in the stagnation period, but re-suspension processes should be considered to modify the relationship between log K ocs and log K ows. Concentration, particle size and composition of resuspended particles could affect the relationship between log K ocs and log K ows. Further work should be done under field conditions, especially where a steady thermodynamic equilibrium state could be assumed.

Distribution patterns of polycyclic aromatic hydrocarbons (PAHs) in the sediments and fish at Mai Po Marshes Nature Reserve, Hong Kong

Sediment samples were collected monthly from eight shrimp shallow ponds (local name gei wais) from July 2003 to January 2004, and from mangrove swamps and inter-tidal mudflats in July and November 2003, respectively. Fish samples (tilapia) were also collected. Polycyclic aromatic hydrocarbons (PAHs) were analyzed by gas chromatography and mass spectrometry (GC/MS). The results indicated that under wet season wet deposition and suspended particulates brought in by nearby rivers, such as the Peal River, served as an important source of PAHs entering Mai Po Marshes. Total organic matter in the sediments showed significant correlations ( p<0.01) with PAHs in the sediments, mainly due to the mechanism that organic matter such as humic substances increased PAH persistence by binding and occluding PAHs. Except for naphthalene, biota-sediment accumulation factors (BSAF) of the PAHs in tilapia were below 1.7, which may be caused by biotransformation and the lower uptake in fish. In addition, aqueous route dominated accumulation of non-biodegradable PAHs in tilapia because higher levels were detected in larger fish than in smaller ones. A general trend was observed that BSAFs declined with the increase of K ow values, which suggested that bioavailability of low K ow isomers was high due to higher gill transfer efficiencies (aqueous uptake) in fish but enhanced biotransformation and decreased gut assimilation (dietary uptake) resulted in decreased accumulation of more hydrophobic PAHs (high K ow). Lastly, viscera appeared to be a promising tissue for biomonitoring, as it contained much higher concentrations than the muscle (3.5 magnitudes), and the levels in the muscle were significantly correlated with those in the viscera ( r 2=0.938, p<0.0001).

Estimating the Octanol–Water Partition Coefficients of NPAHs and PAHs by Solid‐Phase Microextraction and Gas Chromatography‐Ion Trap Detector

The solid‐phase microextraction technique (SPME) was used for the measurement of the partition coefficients of eight nitro polycyclic aromatic hydrocarbons (NPAHs) and ten polycyclic aromatic hydrocarbons (PAHs) between the polymeric coating of polydimethylsiloxane used in SPME and water (K sw). The results demonstrate that the technique is simple, rapid, and reproducible, and thus provides a viable alternative to the conventional methods used for such measurements. There is a strong linear correlation between logK sw and the commonly used logK ow (octanol–water partition coefficient) for PAHs, NPAHs, PCBs, and simple aromatics. The logK ow values for NPAHs range from 2.78 to 4.75, and exhibit a general increase in value with increasing molecular weight. NPAHs are thus noticeably less hydrophobic than their parent PAHs counterparts, for which the log K ow values range from 3.35 to 5.20.

Clouding behavior of nonionic–cationic and nonionic–anionic mixed surfactant systems in presence of carboxylic acids and their sodium salts

The study is focused on evaluation of clouding phenomena of the aqueous single nonionic surfactant system Triton X-100 (TX-100) and its mixed systems with anionic aerosol-OT (AOT) and cationic dodecylpyridinium chloride (DPC) in presence of hydrophobic ions furnished by sodium salts of carboxylic acids, viz., sodium ethanoate, sodium propanoate, sodium butanoate, and sodium hexanoate and the respective carboxylic acids [ethanoic acid, propanoic acid, butanoic acid, and hexanoic acid]. The influence of salts on the cloud point (CP) has been explained on the basis of salt effect as well as the solubilization of higher alkyl chain hydrophobic ions furnished by these salts. Moreover, the co- and counterion effect has been taken into account to explain the variation of the CP in the mixed systems. However, the effect of acids on CP has been explained in the light of their aqueous solubility and their partitioning ability between octanol and water as reflected by their K OW values.

The retention properties of nucleobases in alkyl C 8-/C 18- and IAM-chromatographic systems in relation to log Pow

In order to evaluate the differences in the partition properties of 35 structurally congeneric nucleobases of biological interests in octanol–water biphasic, alkyl C 8/C 18, and IAM systems, a comparative chromatographic study was performed. Comparing with the reversed-phase C 8/C 18 retention data, most of the purines possessed weaker IAM retention except for those with specific H-bond and/or electrostatic interactions. Quantitative correlations between the experimental log P ow literature values and the IAM, C 8, and C 18 log k were evaluated ( R 2 = 0.943, 0.794, and 0.767, respectively). Although IAM retention correlated significantly better (larger R 2 value) with the log P ow values statistically, the latter was revealed apparently behaving more like (slope approaching unity) alkyl C 8/C 18 retention and hence also has the same shortcoming in under-representing analytes capable of forming short-term H-bond/electrostatic interactions with polar head-groups of phospholipids. A chemically meaningful structure-retention model ( q 2 = 0.824 and R 2 = 0.968) was derived, in which the hydrophobic interaction is identified as the underlying factor for the retention of purines in IAM system modulated non-trivially by H-bond/electrostatic interactions.

Water Solubility Enhancement Effects of Some Polychlorinated Organic Pollutants by Dissolved Organic Carbon from a Soil with a Higher Organic Carbon Content

To elucidate the role of a soil humic acid (HA) in the transport of polychlorinated organic pollutants (PCOPs), such as polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans and coplanar-polychlorinated biphenyls, their partition coefficients (K doc) into an HA were compared with their adsorption coefficients (K OC) for a soil with a higher organic carbon (OC) content. The soil sample (ando soil) used in the present study was collected in the same location as the HA. The log K doc values were positively correlated with logarithm of octanol-water partition coefficients (log K OW) of the PCOPs, indicating that the partitioning of PCOPs into the HA was mainly due to hydrophobic interactions. However, the correlation between log K doc and log K OC was negative. This can be attributed to the enhanced water solubility of the PCOPs as the result of the dissolved organic matter from the soil. That is, when the more hydrophobic PCOPs with higher log K OW values are partitioned into the HA, then the larger quantities of PCOPs that are partitioned into the HA are able to dissolve in the aqueous phase. These results suggest that, in a soil with a higher OC content, the HA can serve as more effective carrier of PCOPs from the soil to an aquatic environment.

New approach based on solid-phase microextraction to estimate polydimethylsiloxane fibre coating–water distribution coefficients for brominated flame retardants

A depletion solid-phase microextraction (SPME) method based on multiple SPME extraction was applied to estimate fibre coating–water distribution constants ( K fs) of brominated flame retardants. Several polybrominated diphenyl ethers (PBDEs) including compounds present in the commercial mixture “Pentamix”, and two polybrominated biphenyls (PBBs) were considered as target analytes. One hundred-micrometer poly(dimethylsiloxane) (PDMS) coating fibre was selected to estimate partition coefficients. SPME kinetics studies at 25 and 100 °C were performed. K fs values obtained at both temperatures for brominated flame retardants were compared with the corresponding octanol–water partition coefficients ( K ow) values found in literature. A linear log–log relationship between K ow with K fs was found. To the best of our knowledge, this is the first study where brominated flame retardants K fs values are estimated.

Uptake of Benzene and Alkylbenzenes by Cation- and Anion-Exchange Resins from Aqueous Solutions

Uptakes of benzene and 12 alkylbenzenes (from toluene to n-pentylbenzene including xylene and trimethylbenzene isomers) by both strong acid cation (Dowex 50W-X4 and X8) and strong base anion (Dowex 1-X4 and X8) exchange resins have been studied in aqueous solutions at 25 degrees C; their distribution constants (K) have been determined. The relationship between the octanol-water partition coefficient (K(ow)) and the resin affinity for solutes has been analyzed. The K values of benzene and alkylbenzenes were larger than the K values of aliphatic hydrocarbons expected from the K(ow) values. While the K value was increased with the alkyl chain length, no further increase in the K value was observed for n-butylbenzene and n-pentylbenzene.