Concentrations Of Hydrophobic Compounds Research Articles

Standard Water Generating Vials for Lipophilic Compounds

The study of non-polar compounds in aqueous environments has always been challenging due to their poor solubility in aqueous media. The low affinity of non-polar compounds toward polar solutions facilitates their attachment to glassware, which results in unstable sample concentrations. To address this challenge, and to enable the preparation of a stable mixture of hydrophobic compounds in an aquatic environment, we introduce an in-vial standard water generating system consisting of a vial containing appropriate aqueous solution and a polydimethylsiloxane thin film spiked with target compounds. In this system, a solution with a stable analyte concentration is attained once equilibrium between the thin-film and aqueous solution has been achieved. The developed standard water system was studied using endocannabinoids and phospholipids as model hydrophobic compounds of biological importance, with results indicating that the concentration of hydrophobic compounds in water can remain stable over multiple days. The results also showed that analytes released from the thin film can compensate for analyte loss due to extractions with solid-phase microextraction fibers, thereby re-establishing equilibrium. Thus, the vial is suitable for the repeatable generation of non-polar standards for routine analysis and quality control. The results of this work show that the developed system is stable and reproducible and therefore appropriate for studies requiring the measurement of free concentrations and accurate quantification.

Design of Experiment Approach to Optimize Hydrophobic Fabric Treatments.

Polymer materials can be functionalized with different surface treatments. By applying nanoparticles in coating, excellent antimicrobial properties are achieved. In addition, antimicrobial properties are enhanced by hydrophobic surface modification. Therefore, the goal of this work was to modify the process parameters to achieve excellent hydrophobicity of polymer surfaces. For this purpose, a Design of Experiment (DoE) statistical methodology was used to model and optimize the process through six processing parameters. In order to obtain the optimum and to study the interaction between parameters, response surface methodology coupled with a center composite design was applied. The ANNOVA test was significant for all variables. The results of the influence of process parameters showed that, by increasing the pressure, concentration of hydrophobic compounds and dye concentration, water vapor permeability was enhanced, while by decreasing weight, its efficiency was enhanced. Moreover, the increase in the temperature enhanced water vapor permeability but decreased the resistance to water wetting. An optimal process with ecologically favorable 6C fluorocarbon (68.802 g/L) surpassed all preliminary test results for 21.15%. The optimal process contained the following parameters: 154.3 °C, 1.05 bar, 56.07 g/L dye, 220 g/m2 fabric. Therefore, it is shown that DoE is an excellent tool for optimization of the parameters used in polymer surface functionalization.

Water repellency and distribution of hydrophilic and hydrophobic compounds in soil aggregates from different tillage systems

Water repellency properties of individual soil aggregates offer increased reduction of carbon (C) mineralization within soils. These studies explore the spatial distributions of C and groupings of C–H and C O compounds at multiple soil depths, on surfaces and within multiple sized soil aggregates. Measurements were conducted on soil aggregates, sampled from three horizons in a silty loam Anthrosol under long term grassland pastures and short term conservation tillage wheat and in a silty loam Luvisol subjected to long term conventional tillage of maize. Soil aggregates were fractionated into seven size classes by dry sieving and single aggregates were mechanically separated into external, transitional and interior regions by soil aggregate erosion (SAE) chambers. Soil materials from different aggregate-size classes and aggregate layers were evaluated for total C and nitrogen (N) contents. Functional hydrophobic and hydrophilic groups in each of these soils were identified by DRIFT spectrometry. Water repellency was identified on the surfaces of different size-class aggregates and each of their interior regions by the ethanol/water sorptivity method. Total organic C contents within individual aggregates and size classes varied considerably and were influenced by soil depths and management practices. Whole microaggregates had greater C contents than macroaggregates. Total organic C content was highly correlated to hydrophobic (C–H) groups ( R 2 = 0.78), but not hydrophilic groups. External surfaces of aggregates from no tilled soils of wheat and grass exhibited the largest gradients of hydrophobic C–H groups when compared to their interiors. More hydrophilic C O groups were observed in maize and grassland biomes where plant biomass was greater. Although highly variable, the largest gradients of C O groups were measured in the Ap and Ah horizons of maize and grasslands. Water repellency indices were greater in aggregate sizes ranging from 8 to 5 mm for agricultural soil management systems and were similar for most aggregate sizes measured for grasslands. Soil aggregate water repellency appears to be controlled by the uniform distribution of these compounds at surfaces of all soil aggregate-size fractions and possibly by the concentrations of hydrophobic compounds on surfaces of aggregates at multiple soil depths. Further inquires into the mechanisms controlling soil wetting require more than a quantification of total organic C. These studies demonstrated spatial interactions between the locations and quantities of hydrophobic and hydrophobic compounds distributed among soil aggregate-size fractions located within the soil profile.

Physicochemical principles of hydrophobization of mineral binders by additives produced from peat raw material

The results of theoretical and experimental studies aimed at developing a method for hydrophobization of mineral binders and building materials based on them by additives extracted from the organic matter of peat are presented. The processes occurring in heat treatment of peat are studied by analyzing the conversion of groups of chemical substances contained in peat. An increase in the concentration of hydrophobic compounds in thermal destruction of peat raw material is substantiated. The hydrophobizing effect of the additives is based on the formation of water-repellent adsorption films of bitumen compounds on cement particles. A working hypothesis of the mechanism of their formation is advanced.

Changes to cadmium associations in canal sediments on drying and oxidation

Polycyclic aromatic hydrocarbons (PAHs) are widely distributed in the marine environment. Many PAHs are known to be mutagenic and carcinogenic, so their presence in the environment may constitute a serious threat to the health of humans and ecosystems. Bioremediation has shown promise as a potentially effective and low-cost treatment to eliminate organic pollutants in the environment. However, biodegradation of PAHs in soil or sediment is usually very slow because the bioavailability is limited by a poor mass transfer, since PAHs generally are well known for their low aqueous solubility, high hydrophobicity and tendency to sorb tightly to soil or sediment constituents. Applying surfactants at contaminated site might be one way to facilitate the release of sorbed PAHs from solid matrices and increase the aqueous concentrations of hydrophobic compounds resulting in higher mass transfer rate. Though using chemically produced surfactants has shown promise for significantly reducing time and cost of remediation, the use of these surfactants in environmental treatment processes has been rather limited due to the concerns regarding their toxicity and biodegradation fact. Being biologically synthesized surface-active agents, biosurfactants have the advantages of being readily biodegradable and non-toxic comparable to chemically produced surfactants. This distinct perspective makes them valuable in PAHs bioremediation. In this paper, the effectiveness of anionic rhamnolipid biosurfactant on the desorption and biodegradation of PAHs in sediment slurry was compared with that of synthesized surfactant sodium dodecyl sulfonate (SDS). The artificially fresh-contaminated sediment and aged-contaminated one were used in experiments to determine the effect of aging process on bioremediation. Both biological and chemically synthetic surfactants at high dosages (above effective critical micelle concentration) greatly enhanced desorption of sediment-sorbed phenanthrene, whereas rhamnolipid mixture (Rh-mix) was more efficient than SDS in desorption enhancement. Moreover, Rha-mix showed lower toxicity to the PAH-degrading bacteria. The results of biodegradation experiments showed that the extents of phenanthrene biodegradation were significantly enhanced by both Rha-mix and SDS at the optimal concentrations. When the biodegradation systems amended with rhanmolipid dosages above 400 mg/L and SDS dosages above 5000 mg/L, phenanthrene biodegradation was inhibited because of the mass transfer of phenanthrene from micelle into water. However, Rh-mix at the high concentrations showed lower inhibitory effect on phenanthrene biodegradation than SDS. On the other hand, the lower desorption and biodegradation extent of aged phenanthrene indicated that the aging process could significantly decrease bioavailability of phenanthrene. These results suggested that rhamnolipid may be more effective than SDS in PAH-contaminated sediment remediation processes.

A Simple Liquid Chromatographic Method for Quantitative Extraction of Hydrophobic Compounds from Aqueous Solutions

Abstract We are reporting a rapid, high-capacity liquid chromatographic method for quantitative extraction and concentration of hydrophobic compounds from biological fluids and aqueous solutions. Samples are injected into commerically-available cartridges (Sep-Pak C18R) containing a microparticulate, reversed phase packing which retains hydrophobic compounds. Inorganic salts and organic hydrophilic contaminants are removed with a water wash. Hydrophobic compounds are eluted quantitatively with minimal volumes (∼5 ml) of organic solvents. As demonstrated with radiolabeled taurocholate, thin-layer chromatography, enzymatic fluorimetry and capillary gas chromatography, complete recovery of bile salts from large volumes of urine, serum, amniotic fluid and hydrolysis reaction mixtures was achieved at flow rates up to 20 ml/min. A single cartridge concentrated approximately 50 mg of either taurocholate or the more polar bile salt, taurolithocholate sulfate. The technique is simple and applicable to the isolatio...