Ionizable Organic Compounds Research Articles

Potentiometric determination of octanol–water and liposome–water partition coefficients (logP) of ionizable organic compounds

Abstract The logarithm of the octanol–water partition coefficient, log P, is a key physicochemical property for both pharmaceutical drugs and agrochemicals. It is also required by legislation as part of the physicochemical properties profile for high volume production chemicals. This Letter describes a simple method for determining log P values (over a wide range from −0.8 to 5.3) for 12 organic weak acids and bases using potentiometric titrations, with octanol or phosphatidyl choline liposomes as the partitioning medium. Such titrations take comparatively little time (about 30–45 min per titration), are easy to implement, and can be carried out with an inexpensive laboratory titrator.

POTENSI SENYAWA ORGANIK TIDAK TER-ION DALAM MENGURANGI KELARUTAN BESI (FE) UNTUK MENINGKATKAN PRODUKTIFITAS TANAH SAWAH BUKAAN BARU

The research about potency of non-ionic organic compounds to decrease the dissolved iron (Fe) and to increase productivity of recently used ricefield had been conducted from August 2004 till January 2005. The objective was to study the effect of non-ionic organic compounds applied to control Fe and to increase rice production on recently used ricefield. The experiment used completely randomized design with four treatments and three replications. The treatments were consisted of four levels of non-ionic organic compounds (polysaccaride), those were 0, 75, 150, and 225 ppm. The result of this study showed that the effect of non ionic-organic compounds (polysacaride) at 225 ppm could reduce solubility of Fe2+ from 302,67 to 126,67 ppm for 30 days flooded. The yield of the rice (dry weight of grain and percentage filled out of grain) increased as much as 2,95 g dan 35 % with effect of polysaccaride at 225 ppm. 
 
 Key words : non-ionic organic compounds, polysaccaride, recently used ricefield, flooded.

Sorption of naphthoic acids and quinoline compounds to estuarine sediment

The sorption of 16 ionizable organic compounds (IOCs) to an estuarine sediment was measured in synthetic estuarine water as a function of IOC concentration (1–100 μM) at fixed ionic strength (0.4 M), pH (7.6), and sediment concentration (0.018 g sediment kg − 1 suspension). Of the 16 IOCs, 11 were naphthoic acids and five were quinoline compounds. The linear sorption distribution coefficient ( K d) was used to correlate sorption to IOC physicochemical and molecular characteristics. With respect to naphthoic acid, sorption increased with the addition of ortho-substituent groups and with increasing chain length of the 1-acid group, and the greatest increase occurred with ortho-hydroxyl, carbonyl, and carboxyl groups. With respect to quinoline, sorption decreased with substituent group addition (except for nitro group) and with additional heterocyclic N atoms. For the naphthoic acids, log K d exhibited a positive correlation with water solubility (log S w) indicative of sorption primarily to mineral surfaces under the solution chemistry. For the quinoline compounds, log K d exhibited a negative correlation with log S w and a positive correlation with n-octanol/water partition coefficient (log K OW) indicative of sorption primarily to organic matter. For both compounds, poor or no correlations were established between log K d and acid dissociation constant (p K a1), and between log K d and a variety of molecular connectivity indexes. The results from this study demonstrate that the sorption of IOCs differ depending on their backbone structure and may differ between parent compound and ionizable degradation product.

Three-phase system in solvent bar microextraction: An approach for the sample preparation of ionizable organic compounds prior to liquid chromatography

In this article, a simple new solvent microextraction technique is described for the extraction of ionizable organic compounds. This involves performing simultaneous forward- and back-extraction across an organic film immobilized in the pores of a porous polypropylene hollow fiber. Four chlorophenoxyacetic acid herbicides were chosen as model compounds. The target compounds are extracted from the stirred acidic aqueous sample (adjusted to 0.5 M HCl; donor phase) through a thin film of an organic solvent residing in the pores of a polypropylene hollow fiber; they are then finally extracted into another alkaline aqueous phase (1 M NaOH; acceptor phase). Both ends of the fiber are pressure-sealed. The acceptor phase was analyzed by liquid chromatography (LC). This method gave good enrichment (by a factor of 438–553) of the analytes in 40 min extraction time with reasonably good reproducibility. The analytical potential of the method was demonstrated by applying the method to spiked river water sample.

Effects of ionizable organic compounds in different species on the sorption of p-nitroaniline to sediment

In natural water systems, sorption of an organic pollutant to soil/sediment is often influenced by coexisting organic compounds. For ionizable organic compounds, molecular form may do differently competitive effect from ionic form. In order to examine competitive power of ionizable organic compounds in different forms, effects of some ionizable organic compounds including organic acids and organic bases in molecular form or ionic form on the sorption of p-nitroaniline to a sediment from water were investigated by batch equilibrium experiments. Results exhibit that molecular organic acids are much stronger in competitive power to p-nitroaniline than ionic ones, while ionic ones of organic bases compete with p-nitroaniline stronger than molecular ones. In addition, the competitive powers of coexisting organic acids in molecular form or ionic form in binary-solute systems are good correlated with the nonlinear sorption of cosolutes in single-solute systems, i.e., the stronger nonlinear sorption of the cosolute in single-solute systems, the stronger competitive effect of the cosolute on p-nitroaniline is showed in binary-solute systems. For organic amines, organic cations could be adsorbed through cationic exchange to the sediment more favorably than their molecular forms, and consistently, the former shows stronger competitive power than the latter. These results are of significance for one to describe accurately sorption of ionizable organic compounds in natural environment.

Sorption of hydrophobic ionizable organic compounds (HIOCs) onto polymeric ion exchangers

This study investigates the sorption of synthetic organic compounds, such as benzene sulfonate, naphthalene mono- and disulfonates, onto ion exchangers. These organic compounds exist as aromatic anions in aqueous solutions within a wide range of pH and they are referred to as hydrophobic ionizable organic compounds (HIOCs). Characteristically, the HIOCs contain two primary constituents: non-polar aromatic head groups and ionic charges. Sorption of the HIOCs onto ion exchangers essentially follows an ion exchange stoichiometry; however, ion exchange selectivity is greatly governed by the size of the non-polar head group and ionic charge. The favorable sorption of the HIOCs is unique because they are all endothermic and entropy-driven. The ion exchange selectivity in favor of the HIOCs can be reduced and reversed in cosolvents. Chloride and sulfate are commonly encountered competing ions presented in water systems. The valence of the competing ions influences sorption of the HIOCs onto ion exchangers. An equilibrium model can be used to predict the valence effect of the competing ions.

Evaluation and optimization of an on-line admicelle-based extraction-liquid chromatography approach for the analysis of ionic organic compounds.

Admicelles-based solid-phase extraction (SPE) was on-line coupled with liquid chromatography/electrospray ionization/ion trap mass spectrometry, and it was proposed for the extraction of ionic organic compounds based on the formation of surfactant-analyte ion pairs. The approach was illustrated by studying the preconcentration of quaternary ammonium herbicides (quats) on sodium dodecyl sulfate (SDS) admicelles produced on alumina. Optimization of the parameters affecting SPE were studied on the basis that admicelles are dynamic entities in equilibrium with the aqueous phase. Some general guidelines could be established for method development from the results obtained. Factors influencing on-line operation were elucidated. On-line regeneration of the sorbent in each run was easily achieved by disruption of SDS admicelles with methanol and posterior coating of the alumina with SDS. The recovery of quats from drinking water samples were found quantitative for paraquat, diquat, and difenzoquat and above to 70% for chlormequat and mepiquat. Concentration factors of about 250, using sample volumes of 50 mL, were achieved. The detection limits ranged from 10 to 30 ng/L. The approach developed permits compliance with the directives of the European Community for drinking waters (100 ng/L) and goes deeply into the basis of solid-phase extractions that use surfactant-coated mineral oxide as sorbents.

Sorption of ionizable organic compounds on HDTMA-modified loess soil

A natural loess soil was modified using a cationic surfactant, hexadecyltrimethylammonium (HDTMA) bromide. Sorption of ionizable organic compounds (IOCs), 2,4-dichlorophenol (DCP), p-nitroaniline (NA) and benzoic acid (BA), on the modified soil was determined under different pH conditions. The objective of this study was to examine the sorptive characteristics of IOCs on HDTMA-modified loess soil as a function of pH in an attempt to establish the sorptive models and mechanisms for predicting the sorptive behaviors of IOCs on the HDTMA-modified loess soil. The sorption isotherms of DCP, NA and BA with the soil were obtained using the batch equilibration method. Results indicated that the sorption isotherms of IOCs, regardless of ionic or neutral forms, were non-linear and obeyed to the Freundlich equation. A model describing the sorption of IOCs on the HDTMA-modified loess soil was derived from the experimental data. The model well predicted the sorption of DCP from individual sorption of both ionic and neutral species of the IOC. In binary solute systems, sorption of NA was reduced in the presence of DCP or BA, which indicated that DCP and BA had a competitive effect on the sorption of NA on the HDTMA-modified loess soil. The effect of DCP on the sorption of NA gradually increased with decreasing pH from 10.8 to 6.7, suggesting a stronger effect of neutral DCP than that of the ionic species on the sorption of NA. Modification of loess soil may effectively immobilize ionizable organic contaminants in soil environment.

A method for the prediction of the crystal structure of ionic organic compounds—the crystal structures of o-toluidinium chloride and bromide and polymorphism of bicifadine hydrochloride

The crystal structures of o-toluidinium chloride (1), o-toluidinium bromide (2) and two polymorphs of bicifadine hydrochloride (3) have been determined. The polymorphs of 3 differ in their molecular conformation and in their mode of packing. Crystallisation studies and quantum mechanical calculations show that the more readily crystallisable polymorph grows from the thermodynamically most stable conformer. On heating, conversion to the second polymorph takes place just below the melting point. The crystal structures of 1, 2 and the first polymorph of 3 have been successfully predicted using a procedure that is suitable for simple ionic organics.

Chemical composition of size-resolved atmospheric aerosols in the eastern Mediterranean during summer and winter

The chemical composition of aerosols has been determined in 30 size-resolved samples collected using a Berner low-pressure impactor during two campaigns conducted at a coastal site in the Eastern Mediterranean in July 2000 and in January 2001. Sulfate (SO 4 2−) and ammonium (NH 4 +) have been identified as the main ionic components of the sub-micronic aerosol fraction, with SO 4 2− accounting for up to 38% of the total fine mass and up to 65% of the total ionic mass during both seasons. On the other hand, nitrate (NO 3 −), chloride (Cl −), sodium (Na +) and calcium (Ca 2+) were identified as the main components of the super-micron mode. The ionic organic compounds (including carboxylic, dicarboxylic and ketoacids) were distributed both between sub-micron and super-micron mode, indicating origin from both gas-to-particle conversion and heterogeneous reactions on pre-existing particles. The total water-soluble ionic organic fraction although accounting for only up to 1–2% of both coarse (>1 μm) and fine (<1 μm) mass fractions, accounts for up to 15% of the organic carbon (OC) mass. NH 4 + was found to be significantly correlated to non-sea-salt sulfate (nss-SO 4 2−), with NH 4 +/nss-SO 4 2− molar ratio ranging from 1.3 to 2, the lower ratio associated with transport from the W sector. Chloride depletion was observed mainly during summer and was significantly correlated with NO 3 − concentrations, with a molar ratio of 0.80, indicating the reaction of nitric acid with NaCl as the main source of NO 3 − in the area. Total ionic mass both in the fine and coarse fraction accounted for up to 58% of the total aerosol mass during both seasons. An attempt to perform a mass closure analysis indicates that nss-SO 4 2− and organic carbon are the main components of the fine fraction with relative contributions of 38% and 16%, respectively. In the coarse fraction, the ionic part accounts for 58%, mineral dust for 32% and the remaining non-identified part of 12–30% could be partly attributed to water.

Layered Nanocomposites of Aggregated Dyes and Inorganic Scaffolding

Layer-by-layer thin films were prepared by the alternate deposition of clay particles and ionic organic compounds from solution onto a rigid support. The organic component comprised a monomeric cyanine dye or poly-l-lysine with the same cyanine chromophore appended to it, a dye polymer. Physical measurements indicated that layers of the organic and inorganic materials could be deposited alternately in a repeated fashion with each layer only one to two nanometers thick. Within the film structure the cyanine chromophore exhibits J-aggregate spectroscopic properties, either as the result of adsorption to the clay in the case of the monomeric dye or because it preexisted in this form in the case of the dye polymer. This composite assembly can potentially serve as a model for a light-harvesting photoantenna system. We attempted to demonstrate that by capping the multilayer film with another layer of a different cyanine dye, whose J aggregate absorption band overlapped the fluorescence wavelength of the dye incorporated into the film, acting as an excitation energy donor. Efficient energy transfer was demonstrated for films containing no more than four dye layers for the monomeric donor dye or six layers for the polymeric donor dye. However, close examination of the absorption spectra of the donor−acceptor systems reveals that an interaction appears to occur in the assembly that results in excess acceptor dye being incorporated into the film. This raises the possibility that the acceptor dye penetrates into the film and mixes into the donor dye layers, calling into question whether long-range energy transfer occurs due to an antenna effect.

Structural studies of ambient temperature plastic crystal ionconductors

A number of novel organic ionic compounds based on the pyrrolidinium cationare described which have been found to be ion conductors in their solidstates around room temperature. The properties of the compounds areconsistent with their exhibiting plastic crystal phases. In order tounderstand some of the molecular origins of the plastic crystal behaviourand the ion conductivity that it promotes, a number of related compoundsbased on the imidazolium and ammonium cations are also described which havestructural elements in common with the pyrrolidinium cation, but which donot show the plastic behaviour. It is found therefore that the nature ofthe cation is quite critical to the development of this behaviour. Thealkyl methyl pyrrolidinium cation is found to produce plastic crystalphases when the alkyl chains are short, thereby preserving the ability ofthe cation to rotate with minimal steric hindrance. The ammonium andimidazolium cations of comparable size and structure are less able toproduce these plastic phases, in many cases because the low temperaturephase proceeds to melt rather than forming a stable rotator phase.

Plastic Crystal Electrolyte Materials: New Perspectives on Solid State Ionics

Plastic crystal materials have long been known but have only relatively recently become of interest as solid–state ion conductors. Their properties are often associated with dynamic orientational disorder or rotator motions in the crystalline lattice. This paper describes recent work in the field including the range of organic ionic compounds that exhibit ion conduction at room temperature. Conductivity in some cases is high enough to render the compounds of interest as electrolyte materials in all solid state electrochemical devices. Doping of the plastic crystal phase with a small ion such as Li+ in some cases produces an even higher conductivity. In this case the plastic crystal acts as a solid state “solvent” for the doped ion and supports the conductive motion of the dopant via motions of the matrix ions. These doped materials are also described in detail.

Sorption of atrazine, 2,4‐D, nitrobenzene and pentachlorophenol by urban and industrial wastes

SummaryThis study was carried out to investigate the sorption properties of man‐made soil developed from sewage sludge, municipal wastes, brick and mortar debris, harbour sludge, sand fills, fly ash, and wastes from coking plants and coal mines. The composition of organic matter in the samples was analysed, and the sorption isotherms of four reference chemicals (nitrobenzene, atrazine, 2,4‐D, pentachlorophenol) were determined. Fly ash, which contains up to 89% of its carbon as Black Carbon, showed a strong affinity to all four chemicals. For the other waste materials, a strong correlation between the logarithm of the Freundlich adsorption constant, Kf, and the logarithm of organic carbon, Co, was established (r = 0.85–0.96). This holds for the non‐ionic nitrobenzene and also, within a certain pH range depending on the pKa of the compound, for the three ionizable organic compounds (atrazine: pH &gt; 4; 2,4‐D: pH &gt; 5; PCP: pH &gt; 6). At pH near the pKa value the sorption is sensitive to pH. There were no statistically significant differences between the waste materials and the natural soils in the relations between logKf and logCo for either ionic or non‐ionic chemicals. This result suggests that the method devised for estimating the sorption of organic chemicals in natural soils based on their content of organic carbon is equally valuable for the waste materials, with the exception of fly ash which contains a large amount of Black Carbon.

Chromatographic quantitation of the hydrophobicity of ionic compounds by the use of micellar mobile phases

Many biologically active compounds of interest in structure–activity relationships are ionic at physiological pH. However, ionic organic compounds are only weakly or not retained in conventional RPLC which impedes the chromatographic estimation of their hydrophobicity and the development of quantitative retention–activity relationship studies. The use of micellar mobile phases allows the retention of ionic compounds. Hydrophobic and electrostatic forces govern the retention of ionic compounds in micellar liquid chromatography. In this paper three different retention models log k–log P for ionic compounds are tested ( P=partition coefficient). The retention model (log k= a log P+ b α+ c) which includes the hydrophobicity and the molar total charge of compound at a given pH value has proven to be valid for all types of compounds tested, catecholamines, local anesthetics, diuretics and o-phthalaldehyde–N-acetyl- l-cysteine amino acid derivatives.

Photolysis of metribuzin in oxygenated aqueous solutions

The photochemical behaviour of metribuzin [4-amino-6-(1.1-dimethylethyl)-3-methylthio-1.2.4-triazin-5(4H)-one] and its known metabolites desaminometribuzin (DA), diketometribuzin (DK) and desaminodiketometribuzin (DADK) was investigated in aqueous oxygenated solutions at various pH values. The photochemical degradation of metribuzin over time and the formation and further fate of DA, DK and DADK were elucited. Both side-chain degradation and ring opening were detected as a result of photolysis. Six unknown metabolites as a result of side-chain degradation, including 6-azauracile, 6-azathymine and 4-aminosubstituted derivatives, were identified as very stable photodegradation products. Furthermore, some inorganic and organic ionic compounds were detected such as monocarboxylic, dicarboxylic and ketocarboxylic acids formed by side-chain degradation and ring cleavage.

Chemical and biological aspects of ecotoxicological risk assessment of ionizable and neutral organic compounds in fresh and marine waters: a review

Chemical and biological aspects of ecotoxicological risk assessment of ionizable and neutral organic compounds in fresh and marine waters: a review

ION-PAIR ASSOCIATION OF SUBSTITUTED PHENOLATES WITH K+ IN OCTANOL

The speciation, environmental distribution, and ultimate fate of phenolic compounds, a class of hydrophobic ionizable organic compounds, is influenced by both their hydrophobic and electrostatic characteristics. In this study, electrical conductance measurements were employed to characterize the ion-pair association properties of a monovalent inorganic cation (K+) with substituted phenolate anions in the model hydrophobic solvent, 1-octanol. Quantification of such processes is important for characterizing the overall partitioning to and speciation in octanol of phenolic compounds. Data were analyzed and association constants were calculated using a modified form of the Fuoss–Onsager equation for electrical conductivity. Results indicate that the magnitude of ion-pair association correlates with the electron-donating and -withdrawing characteristics of phenolic ring substituents. A quantitative structure–activity relationship was developed correlating ion-pair association constants to the sum of Hammett substituent constants for each species. The data suggest that for some phenolate salts, charged triple ion or higher aggregate formation may occur at elevated concentrations. A qualitative interpretation of this phenomenon and the selectivity of its occurrence are discussed.

Sorption of the ionizable organic compound, dicamba (3,6-dichloro-2-methoxy benzoic acid), by organo-clays

The sorption of 3,6-dichloro-2-methoxy benzoic acid (dicamba) by hexadecyltrimethyl-ammonium (HDTMA) and dioctadecyldimethylammonium (DODMA) exchanged smectites was studied at different concentrations and pH levels to evaluate the capability of organo-clays to sorb an ionizable hydrophobic compound. Dicamba-organo-clay complexes were also prepared and characterized by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). Results indicated that organo-clays were effective sorbents for dicamba, a water-soluble, ionizable, and potentially mobile organic compound. Organo-clays with higher organic carbon contents usually resulted in greater dicamba sorption. Solution pH significantly affected the sorption of dicamba by organo-clays, with the isotherm inflection point near the dicamba pK a value. Nearly twice as much dicamba could be sorbed in the molecular form as compared to its anionic, deprotonated form. Excessive DODMA contributed to dicamba sorption at pH levels greater than its pK a. Hydrophobic interactions and ionic attractions were responsible for the retention of dicamba by organo-clays.

Characteristics of Phosphorescence of Ionic Organic Compounds Adsorbed on Filter Paper

Abstract The phosphorescence spectra and lifetimes of ionic organic compounds, such as 4-hydroxy-3-methoxybenzaldehyde, 2-amino-1-naphthalene sulfonic acid, and 9-anthracenemethanol, adsorbed on filter paper were measured as a function of the substrate temperature (T) in the range of 93 – 373 K and the preparation concentration (c) of the solutions. The molecule-substrate interaction leading to room temperature phosphorescence is discussed on the basis of the experimental data.