Nonpolar Organic Compounds Research Articles

Fish critical cellular residues for surfactants and surfactant mixtures

The feasibility of using in vitro methods to predict in vivo critical body residue (CBR) for single surfactants and mixtures by measuring the critical cell residue (CCR) in a hepatic fish cell line (PLHC-1C) was investigated. The CCR values were determined using radiochemical methods to measure the test compound partitioning between media and cells at varying concentrations for three distinctly different surfactants (anionic, cationic, and nonionic) and their mixture. The cell median effective concentration (EC50) values for hexadecyltrimethylammonium chloride (C16TMAC), dodecyl hexaethoxylate (C12E6), and sodium dodecylbenzene sulfonate (C12LAS) ranged from 2.9 to 163.3 microM, a 54-fold difference. These cell EC50 values indicate that the cells are several-fold less sensitive to surfactants than whole organisms are. However, based on cellular residue levels for each surfactant and their mixture, only an approximately threefold difference was observed with a range of 0.6 to 1.8 mmol/kg. These concentrations correspond closely to in vivo body burdens (0.2-8 mmol/kg) associated with nonpolar organic or narcosis-acting compounds and their mixtures. The CCRs could provide an alternative and rapid technique to predict CBRs.

The chemical composition of inorganic and carbonaceous materials in PM2.5 in Nanjing, China

PM2.5 samples were collected at an urban and a suburban site in Nanjing, China in 2001. They were analyzed for inorganic ions, elemental carbon, organic carbon (OC), water-soluble organic carbon (WSOC), and individual WSOC and nonpolar organic species. Sulfate and organic matter were the two most abundant constituents in these samples. Sulfate accounted for an average of 23% (urban site) and 30% (suburban site) of the identified aerosol mass. Organic matter accounted for an average of 37% (urban) and 28% (suburban) of the identified aerosol mass. WSOC was a significant portion of OC, accounting for about one-third of OC at the urban site and 45% of OC at the suburban site. The suburban–urban gradient in the WSOC/OC ratio also reflected that the aerosol OC was more aged at the suburban location. The correlations of WSOC with sulfate and nitrate suggest that the WSOC fraction was dominated by secondary organics. More than 30 individual WSOC species in the compound classes of organic anions, amino acids, aliphatic amines, and carbohydrates were quantified, accounting for approximately 8% of the WSOC on a carbon mass basis. In addition, 46 individual nonpolar organic compounds in the compound classes of n-alkanes, hopanes, and polycyclic aromatic hydrocarbons were quantified using an in-injection port thermal desorption technique. These nonpolar organic species accounted for less than 7% of the OC on a carbon mass basis. The quantification of individual compounds allowed the identification of major aerosol sources through principal component analysis. Coal combustion, vehicular emissions, secondary inorganic and organic aerosols, and road/sea salt were the major contributing sources to the identified PM2.5 aerosol mass.

Method for Analysis of Polar Volatile Trace Components in Aqueous Samples by Gas Chromatography

A new method has been developed for direct analysis of volatile polar trace compounds in aqueous samples by gas chromatography. Water samples are injected onto a short packed precolumn containing anhydrous lithium chloride. A capillary column is coupled in series with the prefractionation column for final separation of the analytes. The enrichment principle of the salt precolumn is reverse to the principles employed in conventional methods such as SPE or SPME in which a sorbent or adsorbent is utilized to trap or concentrate the analytes. Such methods are not efficient for highly polar compounds. In the LiCl precolumn concept, the water matrix is strongly retained on the hygroscopic salt, whereas polar as well as nonpolar volatile organic compounds show very low retention and are eluted ahead of the water. After transfer of the analytes to the capillary column, the retained bulk water is removed by backflushing the precolumn at elevated temperature. For direct injections of 120 microL of aqueous samples, the combined time for injection and preseparation is only 3.5 min. With this procedure, direct repetitive automated analyses of highly volatile polar compounds such as methanol or tetrahydrofuran can be performed, and a limit of quantification in the low parts-per-billion region utilizing a flame ionization detector is demonstrated.

Prediction of Subcooled Vapor Pressures of Nonpolar Organic Compounds Using a One-Parameter QSPR

A previously derived empirical linear relationship between the average polarizability of chlorinated aromatic and aliphatic compounds, αm, as calculated using density functional theory methods, and their subcooled liquid vapor pressure, log pL, is tested here for its capability to predict the 25 °C subcooled vapor pressures of a diverse set of nonpolar organic compounds, including 12 brominated benzenes, 13 aromatic hydrocarbons, 10 chlorinated toluenes, 3 hexachlorocyclohexanes, and p,p‘-DDT. A comparison with experimental data shows generally excellent agreement over a 10-order-of-magnitude range in pL, with an average error of less than 0.5 log unit. Experimental vapor pressure values were taken from the literature or, in the case of the chlorinated toluenes, were determined using gas chromatographic retention times. Remarkably large differences in the experimental octanol−air partition coefficients for the isomers of the hexachlorocyclohexanes were found to correspond to similarly large differences in...

Evaluation of Natural and Surfactant-Modified Zeolites in the Removal of Cadmium from Aqueous Solutions

ABSTRACTThe present study involves an investigation on the comparison of a Mexican clinoptilolite-heulandite zeolitic mineral and the modified zeolitic material with the surfactant hexadecyltrimethylammonium bromide (HDTMA) for the removal of cadmium from aqueous solutions. The effects of pH and contact lime on the adsorption process were examined. The optimum pH for adsorption was found to be 7. Cadmium retention reached equilibrium in 32 h and the rate of cadmium adsorption by the zeolites was rapid in the first I Oh. Elovich’s model best described the reaction rate. Batch adsorption experiments conducted at room temperature showed that the adsorption pattern followed the Langmuir-Freundlich isotherm model. The cadmium retention capacity decreased very slightly when the zeolite surface was modified with the surfactant HDTMA, and this material has advantages for its use in the removal of some other contaminants, such as anions and nonpolar organic compounds, like phenols. The results showed that natural zeolite and the surfactant modified zeolite could be considered as potential adsorbents for cadmium removal from aqueous solutions.

Assessment of interfacial mass transfer in water-unsaturated soils during vapor extraction

This paper presents results of a numerical investigation of soil vapor extraction (SVE) systems at the laboratory scale. The SVE technique is used to remove volatile chlorinated hydrocarbons (VCHC) from the water-unsaturated soil zone. The developed numerical model solves equations of flow, transport and interfacial mass transfer regarding an isothermal n-component and three-phase system. The mathematical model is based on a simple pore network and phase distribution model and designed to be scaled by a characteristic length. All mathematical expressions are structured into VCHC specific and VCHC non-specific parameters. Furthermore, indicators are introduced that help to separate thermodynamic equilibrium from thermodynamic non-equilibrium domains and to determine the controlling physical parameters.For numerical solution, the system of partial differential equations is discretized by a finite volume method and an implicit Euler time stepping scheme. Computational effort is reduced notably through techniques that enable spatial and temporal adaptivity, through a standard multigrid method as well as through a problem-oriented sparse-matrix storage concept.Computations are carried out in two dimensions regarding the laboratory experiment of Fischer et al. [Water Resour. Res. 32 (12) 1996 3413]. By varying the characteristic length scale of the pore network and phase distribution model, it is shown that the experimental gas phase concentrations cannot be explained only by the volatility and diffusivity of the VCHC. The computational results suggest a sorption process whose significance grows with the aqueous activity of the less or non-polar organic compounds.

Is rain or snow a more efficient scavenger of organic chemicals?

Abstract Calculations of equilibrium partitioning in the atmosphere are used to quantify and compare the capacity of rain and snow to scavenge gaseous and particle-bound organic contaminants from the atmosphere at different temperatures. Whether snow or rain is more efficient in scavenging organic contaminants depends on the characteristics of the chemical, the characteristics of the snow and atmospheric temperature. At 0°C rain is typically more effective in scavenging the vapors of small organic molecules than snow, because the capacity of the snow surface to sorb such chemicals is smaller than that of liquid water droplets. Snow will, however, be a more effective scavenger for vapors of larger, non-polar organic compounds, which are only sparingly water soluble. The mode of scavenging (vapor vs. particles) and the total scavenging efficiency for such substances will be highly variable and dependent on temperature and the snow characteristics, namely the particle scavenging ratio and the specific snow surface area. To be effectively scavenged by snow, chemicals either need to have an adsorption coefficient at the snow surface KSA of >0.1 m or a particle–air partition coefficient KParticle/Air of >1011 at temperatures below 0°C. Many organic contaminants of concern have such properties. As temperature decreases, more of a chemical partitions from the vapor phase to liquid water droplets, atmospheric particles and the snow surface. This temperature effect is the main reason that snow scavenging ratios are often higher than rain scavenging ratios, especially below −10°C. It is also the reason why wet deposition processes become increasingly important with decreasing temperature, and even constitute the dominant deposition mechanism for some organic contaminants in cold environments.

Is rain or snow a more efficient scavenger of organic chemicals?

Calculations of equilibrium partitioning in the atmosphere are used to quantify and compare the capacity of rain and snow to scavenge gaseous and particle-bound organic contaminants from the atmosphere at different temperatures. Whether snow or rain is more efficient in scavenging organic contaminants depends on the characteristics of the chemical, the characteristics of the snow and atmospheric temperature. At 0°C rain is typically more effective in scavenging the vapors of small organic molecules than snow, because the capacity of the snow surface to sorb such chemicals is smaller than that of liquid water droplets. Snow will, however, be a more effective scavenger for vapors of larger, non-polar organic compounds, which are only sparingly water soluble. The mode of scavenging (vapor vs. particles) and the total scavenging efficiency for such substances will be highly variable and dependent on temperature and the snow characteristics, namely the particle scavenging ratio and the specific snow surface area. To be effectively scavenged by snow, chemicals either need to have an adsorption coefficient at the snow surface KSA of >0.1 m or a particle–air partition coefficient KParticle/Air of >1011 at temperatures below 0°C. Many organic contaminants of concern have such properties. As temperature decreases, more of a chemical partitions from the vapor phase to liquid water droplets, atmospheric particles and the snow surface. This temperature effect is the main reason that snow scavenging ratios are often higher than rain scavenging ratios, especially below −10°C. It is also the reason why wet deposition processes become increasingly important with decreasing temperature, and even constitute the dominant deposition mechanism for some organic contaminants in cold environments.

Adsorption Isotherms of Polar and Nonpolar Organic Compounds on MCM-48 at (303.15, 313.15, and 323.15) K

Adsorption equilibria of four nonpolar molecules (benzene, toluene, hexane, and cyclohexane) and two polar molecules (methanol and acetone) on mesoporous silicate MCM-48 were measured at (303.15, 313.15, and 323.15) K using a gravimetric technique. It was found that MCM-48 has a higher affinity to polar organic compounds than to nonpolar organics. A hybrid isotherm model composed of Langmuir isotherm and Sips equations was applied to fit the adsorption equilibrium data of nonpolar organics including surface adsorption and capillary condensation, while inhomogeneous Dubinin−Astakov (DA) isotherm was used to correlate those of polar organics. The proposed isotherms correlated the measured adsorption data well over the whole range at these experimental conditions.

A simple QSPR model for predicting soil sorption coefficients of polar and nonpolar organic compounds from molecular formula.

A quantitative structure-property relationship (QSPR) model is developed to predict the logarithm of the soil sorption coefficient of 82 organic compounds. The data set contains polar and nonpolar, saturated, unsaturated, aliphatic, aromatic, and polycyclic aromatic compounds covering a log K(oc) range from about 1 to 6 log units. The best correlation equation, containing only five constitutional descriptors (number of benzene rings, molecular weight, number of N, O, and S atoms), predicts log K(oc) with a squared correlation coefficient of 0.94, having a standard deviation, s, of 0.33. The model is validated with an external set of 43 compounds not included in the training set. The descriptors involved in the model can be obtained easily from the molecular formula without any further calculation; therefore, the model is ready to use by environmental scientists with no background in quantum chemistry or chemical graph theory or when no software is available.

Adsorption–Desorption Rate of Nonpolar Volatile Organic Compounds onto Activated Carbon Exemplified by C6H6 and CCl4

This investigation was to evaluate the performance of a thermodynamic model using nonlinear driving force in conjunction with the Langmuir model exemplified by the adsorption of benzene and carbon tetrachloride onto activated carbon in mono- and binary-adsorbate systems. Results show that model-fitted adsorption and desorption rate constants could well predict the adsorption isotherms and breakthrough curves under various conditions. This numerical model can provide adsorption and desorption rate constants. The kinetic parameters are of the same order of magnitude as reported in several studies. Under high reaction temperatures, both the adsorption and desorption rate constants increased while equilibrium constants decreased. A dimensionless valuable C0/K can be used to describe the relationship between adsorbate and adsorbent, and predict the service cycle during the adsorption process. For adsorption in binary mixtures, a high inlet concentration or a low temperature, the weak adsorbate, C6H6, will have...

Is vapor pressure or the octanol–air partition coefficient a better descriptor of the partitioning between gas phase and organic matter?

Abstract Both the sub-cooled liquid vapor pressure (PL) and the octanol–air partition coefficient (KOA) are used to describe the partitioning of non-polar organic compounds between the gas phase and a variety of natural organic substrates in soil, atmospheric particles and foliage. Whether the former is preferable over the latter depends on whether the interaction of the organic compound with the organic matter (OM) resembles more those in the pure liquid than those in liquid octanol. The activity coefficient in octanol (γOct) is a quantitative measure of the difference between these two interactions. An analysis of PL and KOA values for several sets of non-polar and semi-volatile organic compounds (chlorobenzenes, PCBs, PCNs, PCDD/Fs, PBDEs), and of the γOct values derived from these, reveals that γOct tends to range from 1 to 10 suggesting that PL and KOA are very highly correlated. Furthermore, the estimated standard deviation of γOct tends to be so large that PL and KOA are virtually indistinguishable within the measurement uncertainty. Whether γOct within a group of related compounds increases, decreases or stays the same with increasing molecular mass depends on the specific KOA and PL data set used in the calculation of γOct. This implies that with the current precision of KOA, PL and partition coefficients involving OM it is impossible to judge one parameter better than the other.

Use of plasma polymerized highly hydrophobic hexamethyldissilazane (HMDS) films for sensor development

Hexamethyldissilazane (HMDS) plasma polymerized films can be used in a wide variety of applications due to the facility on plasma polymerization of HMDS molecule and the high resistance to acid or basic corrosion of the formed film. Nonetheless, the hydrophobic character, as well as the possibility of adsorption of organic molecules, did not receive attention yet. In this work HMDS plasma polymerized films, presenting high organic character, were obtained in order to analyze their properties as sensors for organic compounds in N 2 and aqueous solutions. The films showed to be not only highly resistant to corrosion in a wide scan of pH, but also presented high water contact angle (approximately 90°). The organic character of the films leads to a high adsorption characteristic for polar and non-polar compounds. The water contact angle measurements vary for 2-propanol aqueous solutions from 90° (0% of 2-propanol) to about 0° (50% of 2-propanol). When HMDS films were deposited on two different substrates, dielectric and porous silicon (PS), two main issues were found. The films suffered degradation by heating and porous silicon was planarized by the plasma deposition, as shown by infrared spectroscopy, optical and Raman microscopy. Deposition on piezoelectric quartz crystal (PQC) showed adsorption of polar and non-polar organic compounds carried by N 2 and chloroform aqueous solutions. HMDS films deposited on silicon were electrically characterized showing quickly and reversible response for 2-propanol carried by N 2. In saturated environment, the electrical current increases about five times when a range of −5 to 0 V was applied. For n-hexane drops, no reversible electrical characteristics were found. Although some issues were revealed, HMDS highly hydrophobic films showed promising characteristics for sensor development.

Solubility of room-temperature ionic liquid in supercritical CO2 with and without organic compounds

Ionic liquid can dramatically dissolve in supercritical (sc) CO2 with polar organic compounds (ethanol, acetone) especially as the concentration of the compounds in scCO2 exceeds 10 mol%, while the effect of a nonpolar organic compound (n-hexane) in scCO2 on the solubility is very limited even when its concentration is as high as 30 mol%.

Temperature-dependent uptake rates of nonpolar organic compounds by semipermeable membrane devices and low-density polyethylene membranes.

The effect of temperature on sampling rates and sampler-water partition coefficients of semipermeable membrane devices (SPMDs) and low-density polyethylene (LDPE) strips was studied in an experimental setup under controlled flow conditions. Aqueous concentrations of chlorobenzenes, polychlorinated biphenyls (PCBs), and polyaromatic hydrocarbons (PAHs) were maintained by continuous circulation of the water over a generator column. Sampling rates for standard design SPMDs (460 cm2) were in the range of 20-200 L d(-1). No significant differences were observed between sampling rates of SPMDs and LDPE strips, but the latter samplers reached equilibrium faster because of their smaller sorption capacity. Sampling rates at 30 degrees C were higher than at 2 degrees C by a factor of about 3. Sampling rate modeling indicated boundary layer-controlled uptake for compounds with log octanol-water partition coefficients smaller than 4.4 and aqueous boundary-layer controlled uptake for more hydrophobic compounds. SPMD-water partition coefficients did not significantly change with temperature, but LDPE-water partition coefficients were larger at 2 degrees C than at 30 degrees C by a factor of 2. For field application of SPMDs, the results imply that temperature is not a key factor that controls uptake rates unless large geographical and temporal scales are involved. The results confirm that water flow velocity has a profound effect on sampling rates.

The application of an open tubular trap in analysis of organic air pollutants.

The paper presents the studies on equilibrium trapping of organic air pollutants. A piece of a commercial capillary chromatographic column coated with polydimethylsiloxane was used for trapping. This kind of the trap was applied for sampling and enrichment of selected volatile nonpolar organic compounds from workplace atmosphere (woodworking shop). In the method developed, which is based on equilibrium trapping the concentration of analytes in a studied medium can be calculated from the partition coefficients determined in a calibration step and the amount of particular analytes trapped. Simultaneously with equilibrium trapping, analytes were sampled into sorbent packed tubes. The concentrations of analytes in woodworking shop atmosphere obtained with both sampling methods (equilibrium and dynamic) were in good agreement.

Estimating octanol-air partition coefficients of nonpolar semivolatile organic compounds from gas chromatographic retention times.

Relative gas chromatographic retention times on a non-polar stationary phase can be used to determine the octanol-air partition coefficient (K(OA)) and the energy of phase transfer between octanol and the gas phase (delta(OA)U) for semivolatile, nonpolar organic compounds. The only prerequisites are knowledge of the temperature-dependent K(OA) of a standard reference compound and directly measured K(OA) values at one temperature for a sufficient number of calibration compounds. It is shown that the technique is capable of predicting the K(OA) of polychlorinated benzenes, biphenyls and naphthalenes as well as polybrominated diphenyl ethers within the environmentally relevant temperature range with an average deviation from directly measured values of <0.2 log units.

Equilibrium chromatographic characteristics of capillary column coated with polytrimethylpropyne for separating polar and non-polar organic compounds by gas capillary chromatography

The temperature dependence (50—180 °C) of the retention factor for 35 hydrocarbons and their oxygen-containing derivatives was studied using a capillary column coated with a new film-forming polymeric adsorbent polytrimethylsilylpropyne (PTMSP). The heats of adsorption for 24 organic polar and non-polar compounds on PTMSP were determined. They turned out to be lower than the heats of adsorption of the same compounds on Porapak Q widely used in gas chromatography. The new adsorbent PTMSP is characterized by high selectivity suitable for practical application.

Acid Hydrolysis Lignin as a Sorbent for Naphthalene

Abstract Lignin, a major polymeric constituent of woody plant tissue, is an abundant source of natural organic matter available as a waste product from the pulp and paper and the fuel ethanol industries. In this study, the sorptive capacity of acid hydrolysis lignin for naphthalene, a representative nonpolar hydrophobic organic compound (HOC), was investigated. When powdered lignin is mixed with distilled water, dissolved and/or colloidal organic matter leaches into the aqueous phase imparting a cloudy yellowish colour. A washing and filtering protocol was developed for pretreating the lignin employed in the sorption studies. Results from batch sorption experiments showed that acid hydrolysis lignin has a strong affinity for naphthalene. The Freundlich isotherm coefficients obtained indicate that the sorption isotherm for naphthalene on hydrolysis lignin is nearly linear. A modified Freundlich equation was employed in order to compare sorption data for HOCs on lignin and activated carbon through the use of unit equivalent coefficients. The results presented in this research and in the literature suggest that the two sorbents are comparable in terms of sorption coefficients. It was determined that acid hydrolysis lignin is unsuitable for use in a packed bed since pumping a naphthalene solution through a column packed with lignin caused the wet lignin to become significantly hardened over time, resulting in a large pressure drop across the system.

Chemical and biological availability of sediment-sorbed benzo[a]pyrene and hexachlorobiphenyl

This study examined the chemical and biological availability of two nonpolar organic compounds, benzo[a]pyrene (BaP) and hexachlorobiphenyl (HCBP), from a spiked sediment that was aged for varying amounts of time. Chemical availability was evaluated using four different solvent combinations to extract chemicals from the sediment. The extractability of BaP and HCBP from sediment using traditional solvents was then compared to the transfer efficiency (TE) of a benthic invertebrate (Lumbriculus variegatus) to relate chemical extractability to bioavailability in the organisms. Results indicated that water was the solvent that best approximated bioavailability for BaP, whereas comparisons for HCBP were inappropriate, because TE values exceeded 100%. The inability to obtain a reasonable TE estimate for HCBP was most likely due to the fact that the oligochaetes received a major portion of their uptake from interstitial water instead of ingestion of sediment particles, which invalidated an important assumption of the TE model. Overall, the results of this study indicate that exhaustive chemical extractions may be an inaccurate representation of the bioavailable fractions for some contaminants.