Nonionic Compounds Research Articles

Prediction of Soil Sorption Coefficients using Model Molecular Structures for Organic Matter and the Quantum Mechanical COSMO-SAC Model

The soil sorption coefficient, K(OC), is an important property affecting the environmental fate of organic molecules. Difficulties associated with measuring K(OC) have led to many attempts to predict this property, but most rely on empirical descriptors for the soil phase determined from correlations with measured K(OC) data, and are thereby limited by the data quality and diversity. A new method is presented to predict K(OC) for nonionic organic compounds that requires only molecular structures. No calibration is performed. Using model humic acid (HA) and fulvic acid (FA) molecular structures from the literature, the soil organic matter is modeled as an organic solvent composed of HA or FA molecules. K(OC) is predicted as an organic solvent-water partition coefficient using the quantum mechanics-based model COSMO-SAC. The log K(OC) values for a set of 440 diverse, environmentally relevant chemicals are predicted with a root-mean-square error of 0.84-1.08, depending on which model HA or FA is used.

The effect of pH on the uptake and toxicity of the bivalent weak base chloroquine tested on Salix viminalis and Daphnia magna

The uptake and accumulation of most electrolytes will change with pH because of the different speciation states of these compounds at various pH. Non-ionized compounds will partition into fatty and organic phases (such as cell membranes) more readily than the corresponding charged compounds, and therefore a higher toxicity can be expected. The current study examines the pH-dependent toxicity and bioaccumulation of the bivalent weak base chloroquine (pK(a): 10.47 and 6.33, log K(OW) 4.67) tested on Salix viminalis (basket willow) and Daphnia magna (water flea). The transpiration rates of hydroponically grown willow cuttings were used to determine the toxicity of chloroquine at pH levels of 6, 7, 8, and 9. Root concentration factors were calculated from solution measurements. Results showed more than 10-fold higher toxicity and four to seven times higher root concentration factor at pH 9 than at pH 6. The toxicity of chloroquine was tested on Daphnia magna using the standard Organisation for Economic Co-operation and Development acute toxicity test modified to accommodate testing at pH levels of 7, 8, and 9. Increasing toxicity was seen at higher pH. The results of the current study confirm that the toxicity of weak bases with intermediate pK(a) values is higher at high pH levels.

Fate of indicator endocrine disrupting chemicals in sewage during treatment and polishing for non-potable reuse

The removal and fate of several indicator endocrine disrupting chemicals (EDCs) at two large municipal wastewater treatment plants (WWTPs) in Adelaide South Australia was investigated. Non-estrogens included the non-ionic surfactant breakdown compounds nonyl phenol mono- and di-ethoxylates, 4-t-octylphenol and 4-nonyl phenol; and, the plasticizer bisphenol A. Estrogens included 17β-estradiol; estrone; and, 17α-ethynylestradiol. Effluent from Bolivar WWTP is polished using stabilisation lagoons followed by coagulation, dissolved air flotation/filtration and chlorination for non-potable reuse. Biosolids from both plants is applied to agricultural land as a soil conditioner. Non-estrogen indicator EDCs were detected at the highest concentration in sewage, effluent and sludge but estrogen indicator EDCs contributed the greatest potential for estrogenicity. The fate of indicator EDCs at various treatment stages is complex and includes biochemical modification/transformation and/or partitioning to either solid or liquid phases. Activated sludge treatment was an important removal barrier achieving moderate-high removal of predicted and YES (a yeast screen assay) measured estrogen equivalent values (EEq). Combined polishing treatment achieved high removal of candidate EDCs (97%). Mass balance indicates that the largest source of estrogenicity discharged from both WWTPs investigated is digested sludge which accounts for 18 and 22% respectively of the combined predicted and YES measured EEq measured in sewage at the two WWTPs.

Synthesis and Reactivity of Rhodium Mono- and Bis(diolefin) Complexes. Characterization of Intermediates in the Rhodium-Catalyzed Cyclotetramerization of Butadiene

Rhodium bis(diolefin) complexes of the general composition [Rh(η4-diene)2(L)]X (diene = butadiene, isoprene, 2,3-dimethylbutadiene; L = PiPr3, PCy3, PtBu2Me, AsiPr3, SbiPr3, CO, CNtBu, CN-2,6-C6H3iPr2; X = CF3SO3, B(Arf)4) were prepared from the nonionic compounds [Rh{μ-O2S(O)CF3}(η2-C8H14)2]2 (1) and [Rh{κ1-OS(O)2CF3}(η4-diene)2] (2−4) as precursors. The reaction of 1 with 1,3-cyclohexadiene led to the formation of [(η6-C6H6)Rh(η4-C6H8)]CF3SO3, whereas from 1 and 6,6′-dimethylfulvene the unsymmetrical sandwich compound [{η5-C5H4CH(CH3)2}Rh{η5-C5H4C(═CH2)CH3}]CF3SO3 was obtained. From [Rh{κ2-O2S(O)CF3}(PiPr3)2] and 1,3-cyclohexadiene or 6,6′-dimethylfulvene the four-coordinated diene complexes [Rh(η4-diene)(PiPr3)2]CF3SO3 were prepared, the cyclohexadiene derivative of which slowly rearranged at room temperature to cis,cis,trans-[Rh{κ2-O2S(O)CF3}(H)2(PiPr3)2] and benzene. Similarly, [Rh(η4-C6H8){κ2-iPr2P(CH2)3PiPr2}]CF3SO3, obtained from [Rh(η4-C4H6){κ2-iPr2P(CH2)3PiPr2}]CF3SO3 and 1,3-cyclohexadiene, rea...

Chemical Clustering for Risk Assessment: Fatty Alcohol Alkoxylates

Abstract Fatty alcohol alkoxylates are non-ionic surface active compounds comprised of a hydrophobic fatty alcohol moiety of variable chain length linked to a hydrophilic polyalkoxylate chain of repeating alkylene oxide subunits containing ethylene and propylene oxides. Materials falling inside this group that are derived from a fatty alcohol and ethylene oxide alone are referred to as fatty alcohol ethoxylates. The unifying features of this class include (1) the use of fatty alcohol fractions drawn from alkyl chains between 4 and 100 carbons in length, each with deliberately wide or narrow ranges and falling within or across specific groups, and (2) the chemical addition to these fractions of specific numbers of repeating structural units of an alkylene oxide in molar ratios ranging from 2 to 100 for ethylene oxide and from 0 to 30 for propylene oxide. A useful rationale establishing the cohesiveness of grouping, or “clustering,” of this family of chemistry is described based on a comparison of similarities across chemical structures contained in the cluster, the continuum of predictable change in associated physiochemical properties, and the accompanying consistency in underlying biological data. A semiquantitative approach is described using the accessible non-confidential information.

Environmental risk assessment for the serotonin re‐uptake inhibitor fluoxetine: Case study using the European risk assessment framework

The serotonin re-uptake inhibitor fluoxetine was selected for an environmental risk assessment, using the most recent European guideline (EMEA 2006) within the European Union (EU)-funded Environmental Risk Assessment of Pharmaceuticals (ERAPharm) project due to its environmental persistence, acute toxicity to nontarget organisms, and unique pharmacokinetics associated with a readily ionizable compound. As a widely prescribed psychotropic drug, fluoxetine is frequently detected in surface waters adjacent to urban areas because municipal wastewater effluents are the primary route of entry to aquatic environments. In Phase I of the assessment, the initial predicted environmental concentration of fluoxetine in surface water (initial PEC(SW)) reached or exceeded the action limit of 10 ng/L, when using both a default market penetration factor and prescription data for Sweden, Germany, and the United Kingdom. Consequently, a Phase II risk assessment was conducted in which green algae were identified as the most sensitive species with a NOEC of <0.6 microg/L. From this value, a predicted no effect concentration for surface waters (PNEC(SW)) of 0.012 microg/L was derived. The PEC/PNEC ratio was above the trigger value of 1 in worst-case exposure scenarios indicating a potential risk to the aquatic compartment. Similarly, risks of fluoxetine for sediment-dwelling organisms could not be excluded. No risk assessment was conducted for the terrestrial compartment due to a lack of data on effects of fluoxetine on soil organisms. The need for a separate risk assessment for the main metabolite of fluoxetine, norfluoxetine, was not conducted because of a lack of fate and effect studies. Based on published data, fluoxetine and norfluoxetine appeared to have a low to moderate bioaccumulation potential, which should be confirmed in formal studies according to OECD guidelines. Exposure assessments for fluoxetine according to the current framework rely heavily on K(OC) and K(OW) values. This approach is problematic, because fluoxetine is predominantly a cationic substance at environmental pH values. Consequently, the fate of fluoxetine (and other ionic substances) cannot be predicted using partition coefficients established for nonionic compounds. Further, published estimates for partition coefficients of fluoxetine vary, resulting in considerable uncertainties in both the exposure and environmental risk assessments of fluoxetine.

ChemInform Abstract: Photoacid and Photobase Generators: Prospects and Their Use in the Development of Polymeric Photosensitive Systems

This article describes the recent progress in the preparation of a set of compounds which can generate acids or bases upon irradiation of light. These compounds are called photoacid generators and photobase generators, respectively. Photoacid generators can be divided into two groups according to their characteristics; i.e., ionic- and non-ionic compounds. Photobase generators are fewer than photoacid generators. These compounds are widely used in the field of polymeric photosensitive systems such as photoinitiated polymerization, photoinduced crosslinking of polymers and oligomers, photoinduced degradation of polymers, and photoinduced transformation of functional groups in polymer chains. In particular, this article focuses on the applications of photoacid and photobase generators to promote the development of photoresist and UV curing materials.

Retention of Nonionic Organic Compounds on Thermally Treated Soils

To achieve a higher efficiency of thermal remediation of soil contaminated with organic compounds, the retention mechanisms of organic compounds on thermally treated soil need to be understood adequately. In this study, a soil-column gas chromatography approach was developed to determine the soil-air partition coefficients (K(SA)) at 300 degrees C for a diverse set of nonionic organic compounds bearing many different functional groups; and the retention mechanisms of these organic compounds on two typical soils, isohumisols and ferralisols, were characterized using a polyparameter linear free energy relationship (pp-LFER). The K(SA) values (mL g(-1)) of typical volatile organic compounds (VOCs) with lower boiling points were <1.5 and in some cases even below 1.0, suggesting the rapid removal of VOCs from soils at 300 degrees C. Moreover, the K(SA) values were found to be a strong function of the soil-column temperature T (K), and be almost independent of the carrier-gas flow rate. Significant differences in molecular interactions were noted among various soil-solute pairs. The relative contributions of nonspecific van der Waals forces to the retention of test polar solutes were higher on isohumisols than on ferralisols. In contrast to the reported pp-LFER models for natural soils and soil components at normal environmental temperatures, our results suggest that elevated temperature remarkably reduces H-bond interactions between polar organic compounds and the soil matrix, thus allowing accelerated desorption of polar organic compounds from soils during thermal treatment.

Systems based on nonionic amphiphilic compounds: aggregation and catalytic properties

The micellization properties, solubilization capability, and catalytic effect of conventional nonionic surfactants and amphiphilic compounds of oligomeric (Tyloxapol) and polymeric (Synperonic F-68, Pluronic F-127) structure were compared. The systems studied demonstrate a marked catalytic effect toward basic hydrolysis of p-nitrophenyl laurate, which exceeds the effect of aqueous alkali solutions by two orders of magnitude. Correlations between the solubilization capacity of aggregates and their catalytic effect were observed. The maximum efficiency was found for the Tyloxapol solution. The synergetic enhancement of the catalytic effect was observed for the mixed Tyloxapol-cetyltrimethylammonium bromide systems in the presence of small amounts of cationic surfactant

QSPR Modeling of Bioconcentration Factors of Nonionic Organic Compounds

The terms bioaccumulation and bioconcentration refer to the uptake and build-up of chemicals that can occur in living organisms. Experimental measurement of bioconcentration is time-consuming and expensive, and is not feasible for a large number of chemicals of potential regulatory concern. A highly effective tool depending on a quantitative structure-property relationship (QSPR) can be utilized to describe the tendency of chemical concentration organisms represented by, the important ecotoxicological parameter, the logarithm of Bio Concentration Factor (log BCF) with molecular descriptors for a large set of non-ionic organic compounds. QSPR models were developed using multiple linear regression, partial least squares and neural networks analyses. Linear and non-linear QSPR models to predict log BCF of the compounds developed for the relevant descriptors. The results obtained offer good regression models having good prediction ability. The descriptors used in these models depend on the volume, connectivity, molar refractivity, surface tension and the presence of atoms accepting H-bonds.

Estratégias de pré-concentração em eletroforese capilar: parte 2. Manipulação da velocidade da fase dispersa/secundária

This work describes CE preconcentration strategies based on the effect of manipulation of the disperse/secondary velocity. Introduced by Terabe et al. in 1984, micellar electrokinetic chromatography is a powerful separation approach that increases the usage of electrokinetic phenomena for the separation of nonionic compounds. The main disadvantage of MEKC is the low concentration sensitivity associated with the limited optical path length for on-capillary photometric detection and the limited volume of sample solution that can be injected. This paper compiles on-line concentration strategies for neutral analytes by sample stacking and sweeping in micellar electrokinetic chromatography.

Factors affecting the adsorption of trichloroethylene onto activated carbons

In this work, an experimental study aimed at the assessment of the factors affecting the adsorption of trichloroethylene (TCE) from water solutions onto activated carbons is presented. The influence of sorbent properties, such as B.E.T. surface area, micropore volume, chemical composition and acid/basic surface functional groups on TCE adsorption capacity is experimentally assessed by testing a set of 12 sorbents. Moreover, the effect of the presence of other species in solution, such as sodium acetate and tetrachloroethylene (PCE), is studied through parametric TCE adsorption isotherms realization. The experimental results show that the TCE adsorption capacity is promoted by a high B.E.T. surface area, micropore volume and C content and it is significantly affected by the presence of a non-ionic compound of similar structure (PCE), however it does not depend on the presence of an organic salt (sodium acetate). These results confirm that neither TCE–carbon ionic interaction nor sorbent ionization phenomena are involved in the TCE adsorption, since its mechanism is based on dispersion forces (London–Van Der Walls interaction). A thorough analysis of the experimental data set suggests that, in consideration of the TCE adsorption mechanism, the maximization of basal plane extent (as the B.E.T. surface area) and its effective fraction (as the C content) is a valid criterion to select or synthesize a new suitable sorbent for TCE adsorption from waters.

Solvent Properties Governing Solute Partitioning in Polymer/Polymer Aqueous Two-Phase Systems: Nonionic Compounds

The solvatochromic solvent parameters characterizing the solvent polarity (pi*), solvent hydrogen-bond donor acidity (alpha), and solvent hydrogen-bond acceptor basicity (beta) of aqueous media were measured in the coexisting phases of nine different aqueous polymer/polymer two-phase systems (ATPS), containing 0.15 M NaCl in 0.01 M phosphate buffer, pH 7.4. Partitioning coefficients of six neutral compounds were measured in the nine ATPS at particular polymer concentrations. The solvatochromic equation was used to describe the partitioning of each compound. Three descriptors of the solvent properties of the phases could describe adequately the partitioning of the solutes in all the ATPS employed.

Emulsion Properties and Phase Equilibrium and of New Asymmetric Gemini Surfactants Consisting of Fatty Acid Esters of Polyethoxylated Alcohol or Phenol

AbstractThe emulsion and phase properties of water‐surfactant systems are reported for nonionic surface active compounds of the asymmetrical gemini type resulting from the esterification of a polyethoxylated alcohol and a fatty acid. These products exhibit typical gemini surfactant properties, in particular, low critical micelle concentration (CMC) and good emulsifying properties, and they often form a gel depending on the temperature and concentration.

Intestinal Absorption and Secretion Mechanism of Carboxylate Drugs

Oral drug delivery is generally the most desirable means of administration, mainly because of patient acceptance, convenience in administration. Intestinal absorption mechanisms of anionic drugs have been mainly explained by the passive diffusion of nonionized compounds. However, several studies have suggested the involvement of specific transporters in intestinal absorption of weak acids including monocarboxylates. (-)-N-(trans-4-Isopropylcyclohexanecarbonyl)-D-phenylalanine (nateglinide) is a oral hypoglycemic agent possessing a carboxyl group and a peptide-type bond in its structure. Although nateglinide quickly reaches the maximal serum concentration after oral administration, nateglinide itself is not transported by PepT1 or MCT1. We demonstrated that nateglinide transport occurs via a single system that is H(+) dependent but is distinct from PepT1 or MCT1. In clinical, patients usually take many kinds of drugs at the same time. Thus, drug-drug interactions involving transporters can often directly affect the therapeutic safety and efficacy of many drugs. However, there have been few studies on food-drug interactions involving transporters. Dietary polyphenols have been widely assumed to be beneficial to human health. Polyphenols are commercially prepared and used as functional foods. We reported that ferulic acid, which is widely used as a functional food, affects the transport of clinical agents. The major dose-limiting toxicity after administration of irinotecan hydrochloride, 7-ethyl-10-(4-[1-piperidino]-1-piperidino)-carbonyloxycamptothecin (CPT-11) is severe diarrhea. We have found that a specific transport system mediates the uptake of active metabolite 7-ethyl-10-hydroxycamptothecin (SN-38) across the apical membrane in Caco-2 cells. Baicalin and sulfobromophthatlein inhibit this transporter. Inhibition of this transporter would be a useful means for reducing late-onset diarrhea.

Effect of mixed liquor pH on the removal of trace organic contaminants in a membrane bioreactor

Experiments were conducted over approximately 7 months to investigate the effects of mixed liquor pH (between pH 5 and 9) on the removal of trace organics by a submerged MBR system. Removal efficiencies of ionisable trace organics (sulfamethoxazole, ibuprofen, ketoprofen, and diclofenac) were strongly pH dependent. However, the underlying removal mechanisms are different for ionisable and non-ionisable compounds. High removal efficiencies of these ionisable trace organics at pH 5 could possibly be attributed to their speciation behaviour. At this pH, these compounds exist predominantly in their hydrophobic form. Consequently, they could readily adsorb to the activated sludge, resulting in higher removal efficiency in comparison to under less acidic conditions in the reactor. Removal efficiencies of the two non-ionisable compounds bisphenol A and carbamazepine were relatively independent of the mixed liquor pH. Results reported here suggest an apparent connection between physicochemical properties of the compounds and their removal efficiencies by MBRs.

Experimental and statistical analysis of trichloroethylene adsorption onto activated carbon

Adsorption processes have long been used in water and wastewater treatment and a deterministic approach has been often adopted for the analysis of fundamental mechanisms. In this research, a new approach based on statistical treatment of modelling data is adopted for the analysis of trichloroethylene (TCE) adsorption on granular activated carbon (GAC) from synthetic groundwater. The work starts from an experimental analysis aimed at the assessment of the influence of thermodynamic parameters (concentration, pH, salinity, temperature and the presence of an organic non-ionic compound, i.e. ethyl acetate) on TCE adsorption capacity. A wide range of process parameters have been considered to simulate highly polluted groundwater, as when leachate infiltrations occur at solid waste landfill. Experimental results show that adsorption capacity decreases by increasing the temperature and the ethyl acetate concentration, while neither pH nor salinity have any influence. A thorough understanding of adsorption mechanism and the individuation of the model with highest physical and mathematical significance is carried out by a thermodynamic analysis and a statistical methodology based on Analysis of Variance (ANOVA). The latter indicates that in dilute solutions the Freundlich model is the best data fitting model for TCE adsorption, among those which are commonly adopted.

Differences in phytotoxicity and dissipation between ionized and nonionized oil sands naphthenic acids in wetland plants

Naphthenic acids (NAs) are composed of alkyl-substituted acyclic and cycloaliphatic carboxylic acids and, because they are acutely toxic to fish, are of toxicological concern. During the caustic hot-water extraction of oil from the bitumen in oil sands deposits, NAs become concentrated in the resulting tailings pond water. The present study investigated if dissipation of NAs occurs in the presence of hydroponically grown emergent macrophytes (Typha latifolia, Phragmites australis, and Scirpus acutus) to determine the potential for phytoremediation of these compounds. Plants were grown with oil sands NAs (pKa approximately 5-6) in medium at pH 7.8 (predominantly ionized NAs) and pH 5.0 (predominantly nonionized NAs) to determine if, by altering their chemical form, NAs may be more accessible to plants and, thus, undergo increased dissipation. Whereas the oil sands NA mixture in its nonionized form was more toxic to wetland plants than its ionized form, neither form appeared to be sequestered by wetland plants. The present study demonstrated that plants may selectively enhance the dissipation of individual nonionized NA compounds, which contributes to toxicity reduction but does not translate into detectable total NA dissipation within experimental error and natural variation. Plants were able to reduce the toxicity of a NA system over 30 d, increasing the median lethal concentration (LC50; % of hydroponic solution) of the medium for Daphnia magna by 23.3% +/- 8.1% (mean +/- standard error; nonionized NAs) and 37.0% +/- 2.7% (ionized NAs) as determined by acute toxicity bioassays. This reduction in toxicity was 7.3% +/- 2.6% (nonionized NAs) and 45.0% +/- 6.8% (ionized NAs) greater than that in unplanted systems.

Electro-membrane reactor for separation and in situ ion substitution of glutamic acid from its sodium salt

An electro-membrane reactor with four compartments (EMR-4) (anolyte, catholyte and comp. 1 and 2) based on in-house-prepared cation- and anion-exchange membrane (CEM and AEM, respectively) was developed to achieve separation and recovery of glutamic acid (GAH) from its sodium salt by in situ ion substitution and acidification. The physicochemical and electrochemical properties of CEM and AEM were characterized and its suitability was assessed in operating environment. The separation of GA − from the mixture of nonionic organic compounds and further ion substitution was achieved by EMR-4. But the higher energy consumption (5.75 kWh/kg of GAH produced), low current efficiency (50.5%) and recovery of GAH (57.2%) in this process were main obstacles for the industrial exploration of the process. Latter, electro-membrane reactor with three compartments (EMR-3) (anolyte, catholyte and central compartment) was developed based on CEMs for only in situ ion substitution of GANa to achieve GAH, in which GA − was not allowed for electro-migration from its feed compartment. CE and recovery of GAH were close to 73% and 96% that indicate the suitability of the EMR-3 process for industrial application over the EMR-4. It was concluded that EMR-3 was efficient as compared to EMR-4 for separation and recovery of GAH from fermentation broth by in situ ion substitution in eco-friendly manner.

Impact of Renal Impairment on Long-Term Retention of Gadolinium in the Rodent Skin Following the Administration of Gadolinium-Based Contrast Agents

Several publications have suggested a possible association between Gd-based contrast agents (GBCAs) and the development of nephrogenic systemic fibrosis, a rare but serious disease. To date, nephrogenic systemic fibrosis has been observed only in patients with severe renal insufficiency.The aim of this study was to determine the impact of a prolonged circulation time of GBCAs caused by reduced renal clearance on the long-term retention of Gd in the skin of rats after administration of different GBCAs. Renally impaired Han Wistar Rats (5/6-nephrectomized rats) were injected with Omniscan, OptiMARK, Magnevist, or Gadovist. The contrast agents were administered once daily for 5 consecutive days into the tail vein at a dose of 2.5 mmol Gd/kg b.w. Skin biopsies were taken at various time points, and the gadolinium (Gd) concentration was determined by inductive coupled plasma mass spectrometry (ICP-MS) over an observation period of 168 days post injection (p.i.). Differences in the skin Gd concentrations were observed between the 4 investigated GBCAs. For the nonionic linear compounds, Omniscan and OptiMARK, high Gd concentrations were maintained in the skin over the observation period of up to 168 days p.i. For the ionic linear compound, Magnevist, comparatively lower Gd retention in the skin was observed over time. For the macrocyclic compound, Gadovist, the Gd values in the skin were even lower, and significantly lower than Gd values in the skin in Omniscan and OptiMARK treated animals. The results of this preclinical study support the use of 5/6-nephrectomized rats as a model for prolonged circulation time of GBCAs as seen in patients with severe renal impairment. Surgically induced severe renal impairment resulted in delayed clearance of the administered GBCAs in the study animals. The highest amount of Gd was observed in the skin after treatment with the nonionic linear GBCAs, whereas the lowest Gd values were observed after treatment with the macrocyclic agent. This suggests that the difference in the Gd values observed in rat skin tissue after treatment with the different GBCAs is caused of a different propensity of the different GBCAs to release Gd in vivo. However, the analytical method used does not distinguish between chelated and unchelated Gd.