Acid Esters In Water Research Articles

Aryl Crown Ethers Based on d‐Glucose Scaffold – Highly Selective Receptors of Amino Acid Ester Hydrochlorides

AbstractAmino acids are important biomolecules with a broad scope of applications in chemical and biological sciences. Their functions and properties depend on their absolute configuration. Therefore, methods for chiral recognition and separation of amino acids are highly sought after. For the purposes of diagnostic and medicinal applications chiral recognition of amino acids in water is particularly relevant. However synthetic receptors for enantioselective binding of amino acids in aqueous media are rare. Recently we reported a d‐glucose‐based crown ether for chiral recognition of amino acid esters in water. We achieved enantioselectivities towards amino acids with hydrophobic sidechains which were among the highest ever reported for a small molecule receptor. The binding affinities were however moderate. Herein we disclose analogs of that receptor, containing aryl functionalities in the crown ether fragment. The new receptors show considerably improved binding affinities for amino acid ester hydrochlorides in water, while retaining high enantio‐ or chemoselectivities.

Research progress on the removal of phthalic acid esters in water

Phthalic acid esters (PAEs), as a kind of persistent organic pollutants, are classified as environmental hormones, and their estrogenic effects can cause great harm to the reproductive system and nervous system of the organism. The environmental pollution and toxicological effects caused by this substance have received global attention, so how to effectively remove PAEs in the environment has become a current research hotspot. This paper summarizes and reviews the common removal methods of phthalates in water, including physical methods, biological methods and chemical methods, and finally prospects for future development.

Residue levels and spatial distribution of phthalate acid esters in water and sediment from urban lakes of Guangzhou, China

The residue levels and composition profiles of phthalate acid esters (PAEs) in water and sediment samples were investigated in eight urban lakes of Guangzhou, China. A total of 23 water and 16 sediment samples were collected. Results showed that all target PAEs were detected with dimethyl phthalate and di(2-ethylhexyl) phthalate as the most abundant compounds. The total concentrations of PAEs from different urban lakes were in the range of 273–1173 ng/L for water and 16.5–242 ng/g for sediments, with the geometric mean of 515 ng/L and 75.0 ng/g, respectively. Zhongshan Park Lake and Liwan Lake were the most highly contaminated with PAEs in water and in sediment, respectively. The spatial distribution of PAEs exhibited that distribution coefficients of PAEs between sediment and water are consistent with hydrophilicity of PAEs, and pollution levels and characteristics of PAEs in different lakes had a close relationship with the geographical location of the lake, industrial and commercial types, population density, and the association between the lake and the Pearl River. According to Pearson correlation analysis, PAEs would be derived from similar or identical sources. Risk assessment suggested that the exposure of PAEs in Guangzhou has a moderate toxicity at the current level.

Preparation and application of a magnetic plasticizer as a molecularly imprinted polymer adsorbing material for the determination of phthalic acid esters in aqueous samples.

A novel magnetic plasticizer molecularly imprinted polymer adsorbing material (MIP@mSiO2 -β-CD@Fe3 O4 ) was successfully synthesized for the determination of six phthalic acid esters in water, milk, and wine samples. The molecularly imprinted polymers were prepared via precipitation polymerization and a surface molecular imprinting technique, using a cyclodextrin-modified magnetic meso-porous material (mSiO2 -β-CD@Fe3 O4 ) as a magnetic supporter, dibutyl phthalate and butyl benzyl phthalate as the dual template molecules, methacrylic acid as the functional monomer, and ethyleneglycol dimethacrylate as the cross-linking agent. The polymers were characterized by scanning electron microscopy, IR spectroscopy, and X-ray powder diffraction. Thermogravimetric analysis and static and dynamic adsorption experiments were carried out to assay its stability and selectivity. Under optimal experimental conditions, a magnetic solid-phase extraction with MIP@mSiO2 -β-CD@Fe3 O4 coupled to gas chromatography and mass spectrometry method was successfully developed for the determination of phthalic acid esters. The established method achieved a good linear range of 0.10∼8.00μg/mL (R>0.99) and a low detection limit within the range of 1.0∼5.0μg/L. An average recovery rate of 80.2∼103% with relative standard deviation<6.7% was obtained upon the application of the developed method to detect phthalic acid esters in actual aqueous samples.

Distribution and sources of polycyclic aromatic hydrocarbons and phthalic acid esters in water and surface sediment from the Three Gorges Reservoir

Distribution and sources of polycyclic aromatic hydrocarbons and phthalic acid esters in water and surface sediment from the Three Gorges Reservoir

Distribution and sources of polycyclic aromatic hydrocarbons and phthalic acid esters in water and surface sediment from the Three Gorges Reservoir

After the impoundment of the Three Gorges Reservoir (TGR), the hydrological situation of the reservoir has changed greatly. The concentration and distribution of typical persistent organic pollutants in water and sediment have also changed accordingly. In this study, the concentration, distribution and potential sources of 16 polycyclic aromatic hydrocarbons (PAHs) and 6 phthalic acid esters (PAEs) during the water drawdown and impoundment periods were investigated in water and sediment from the TGR. According to our results, PAHs and PAEs showed temporal and spatial variations. The mean ΣPAH and ΣPAE concentrations in water and sediment were both higher during the water impoundment period than during the water drawdown period. The water samples from the main stream showed larger ΣPAH concentration fluctuations than those from tributaries. Both the PAH and PAE concentrations meet the Chinese national water environmental quality standard (GB 3838-2002). PAH monomers with 2–3 rings and 4 rings were dominant in water, and 4-ring and 5–6-ring PAHs were dominant in sediment. Di-n-butyl phthalate (DBP) and di-2-ethylhexyl phthalate (DEHP) were the dominant PAE pollutants in the TGR. DBP and DEHP had the highest concentrations in water and sediment, respectively. The main source of PAHs in water from the TGR was petroleum and emissions from coal and biomass combustion, whereas the main sources of PAHs in sediments included coal and biomass combustion, petroleum, and petroleum combustion. The main source of PAEs in water was domestic waste, and the plastics and heavy chemical industries were the main sources of PAEs in sediment.

Determination of o-phthalic acid esters in water by chromatography–mass spectrometry with emulsion dispersive liquid–liquid microextraction preconcentration

Using emulsion dispersive liquid–liquid microextraction preconcentration and injection of a large volume of an extract (10 μL), the limits of chromatographic–mass spectrometric detection of o-phthalic acid esters in water have been attained at the level 4 × 10–6–1 × 10–5 mg/L. The main source of the systemic error of the determination of impurities was found to be the release of o-phthalates from microparticles of chromatographic septum to the carrier gas. The extractant (n-octane) was purified by Rayleigh distillation. The independence of the concentration coefficient of the studied o-phthalates of concentration in the range (0.4–30) × 10–4 mg/L has been demonstrated. The relative expanded uncertainty of the determination of o-phthalates has been calculated and equals 12–39%.

Preparation of Fe3O4@PPy magnetic nanoparticles as solid-phase extraction sorbents for preconcentration and separation of phthalic acid esters in water by gas chromatography-mass spectrometry.

The purpose of this paper is to introduce a solid-phase extraction method of separating and determining of phthalic acid esters (PAEs) by PPy-coated Fe3O4 magnetic nanoparticles (Fe3O4@PPy MNPs). In the process, nanoparticles were served as sorbents and the optimal conditions of the extraction have been explored. The composite was synthesized through the chemical oxidation method, combining pyrrole monomer with Fe3O4 magnetic ball in the form of aggregation state and the coated nanoparticles possessed core-shell construction. The PPy-coated Fe3O4 magnetic microspheres have been extensively characterized by transmission electron microscopy, Fourier transform infrared spectroscopy and vibrating sample magnetometry. The optimum conditions were investigated by orthogonal experimental design, which was used to testing the influence of main factors and the interactions among them. The orthoplan is famous for the merit that it can study the whole experiments comprehensively through minimal tests. Under the optimal extraction conditions: 20mg of modified magnetite nanoparticles, eluting with acetic ester of 2mL, 40min of MSPE, eluting in 1h and 20mL of sample volume, good linearity (r(2)>0.9912) of all calibration curves was obtained in validation experiments. And the limits of detection (LODs) were from 0.006 to 0.021ng/mL. The recoveries in different sample matrices were in the range from 80.4% to 108.2% with relative standard deviations less than 12.8%. The present work demonstrates the applicability of the developed method for the determination of PAEs in water sample and the results justified that it can be applied successfully to the selective isolation and enrichment of PAEs in real water samples.

Sonophotolytic degradation of phthalate acid esters in water and wastewater: Influence of compound properties and degradation mechanisms

The influence of physicochemical properties on the sonolytic and sonophotolytic degradation of a group of short-chain phthalate acid esters (PAEs) was investigated in this study. A 400kHz ultrasonic system and a photolytic system at 253.7nm were employed separately and together, and both pure water and secondary effluent were used as the water matrices. It was found that PAEs with greater hydrophobicity demonstrated more rapid sonolysis and exhibited greater competitiveness in sonochemical reactions in the presence of other compounds. However, although a greater compound hydrophobicity is beneficial for the sonochemical degradation of PAEs, the observed synergy between ultrasound and UV in the sonophotolytic process is reduced owing to the lower accumulation of H2O2 in the aqueous phase. For the sonophotolysis of PAEs in secondary effluent, it was found that PAEs with greater hydrophobicity experienced less inhibition or competition from the background organic substances (expressed as TOC). Identification of prominent degradation intermediates of di-n-butyl phthalate (DBP), as a representative PAE, indicated that hydroxylation of the aromatic ring and butyl-scission of the aliphatic chain are the principal degradation mechanisms. The combined process of US/UV produced a greater degree of DBP mineralization than either US or UV alone (17% TOC reduction within 90min).

Determination of Phthalate Acid Esters in Water and Sediment Samples by GC–MS

Water and bottom sediment samples were taken from the Zhenjiang section of the lower reach of Yangtze River, China during the autumn of 2011, aimed to study the pollution levels of six kinds of phthalate acid esters (PAEs). Water samples were prepared by solid-phase extraction (SPE) and analyzed by gas chromatography-mass spectrometry (GC–MS), with spiked recoveries ranging from 33.5% to 121.0%. Sediment samples were pretreated using ultrasonic-assisted organic solvent extraction, with recoveries varying from 43.7% to 107.6%. Results showed that the concentration levels of PAEs are below the limit of detection (LOD) –63.3μg/L in the water samples of Yangtze River. Tongji River water are severely contaminated by PAEs, with the concentrations of di-n-butyl phthalate (DnBP) up to 613ug/L. Four of PAEs were detected in the tap water of Zhenjiang. It was also found that all of detected PAEs are dominantly partitioned on suspended solids in water samples. The concentrations of PAEs in sediment samples are ranged from &lt;LOD to 7.5mg/kg.

Assay of artemether, methylparaben and propylparaben in a formulated paediatric antimalarial dry suspension

Two HPLC–UV methods are described for the separate determination of artemether (AM) and the combined preservatives, methylparaben and propylparaben in a pharmaceutical dosage form. These analytes are contained in a dry suspension with a high amount of non-soluble excipients, some of which can interfere with the analysis. This makes their separation and analysis of the actives complex. Moreover, due to the wide difference in concentrations, the three analytes could not be quantitated simultaneously. Artemether was analysed using a reversed-phase Nucleosil ® C 18 column [5 μm, 125 mm × 4 mm (i.d.)] with a mixture of acetonitrile: potassium phosphate buffer pH 5.0 (0.05 M): water [48:32:10 (v/v/v)] as mobile phase. Due to the low solubility of the hydroxy benzoic acid esters in water, their sodium salts were used in the formulation. Complete separation of these preservatives was achieved on the same type of column as artemether using as eluent acetonitrile: potassium phosphate buffer pH 5.0 (0.05 M) (30:70, v/v). Quantitation was achieved with UV detection at 215 nm for artemether and 254 nm for the parabens, respectively. And in both methods, pump flow rate was 1.0 ml/min, sample injection volume 20 μl, ambient temperature maintained and no prior sample extraction methods were necessary throughout the experiments. Calibration curves were linear at concentration ranges of 4–16 μg/ml, 1–4 μg/ml and 1–10 mg/ml for methylparaben, propylparaben and artemether respectively. The excipient powder interference could be eliminated by diluting the sample and the analytes eluted at relatively short times using these systems. Both methods were further validated in terms of specificity, linearity, precision and accuracy. The procedures prescribed here are simple, selective and can be used for routine quality control and stability indicating tests involving the analysed compounds formulated in complex matrices.

Phase Behavior of Pentaglycerol Monostearic and Monooleic Acid Esters in Water

The phase behavior in water of pentaglycerol monostearate (C18G5) and pentaglycerol monooleate (C18:1G5) surfactants has been studied as a function of temperature and surfactant weight fraction, W s . The equilibrium phases present at each composition and temperature studied were characterized by means of visual observation under normal and polarized light, differential scanning calorimetry (DSC), and X‐ray scattering, both at small (SAXS) and at wide angle (WAXS). In the temperature range 0–46°C, C18G5 presents a thermotropic α‐gel structure. However, at higher temperatures, the α‐gel phase melts and a lamellar liquid crystalline (Lα) phase is formed. The amount of water that can be solubilized by α‐gel and Lα was determined by plotting the interlayer distance, d, as a function of the reciprocal of W s . Water is soluble in the α‐gel phase up to 21 w/w% water concentration and in the Lα phase up to 30 w/w% water concentration. At higher water concentrations, excess water appears and a dispersion of α‐gel (α‐gel+W) and lamellar liquid crystal (Lα+W) in water is formed, respectively. In contrast, C18:1G5 is liquid in the whole range of temperatures studied (0–100°C). While at low temperatures, C18:1G5 presents a Lα structure, at about 63°C Lα melts and an isotropic liquid reverse micellar solution (Om) phase is formed. The amount of water that can be solubilized by both Om and Lα increases with temperature.

PFGSE–NMR study of the self-diffusion of sucrose fatty acid monoesters in water

The micellization of pure monosubstituted sucrose fatty acid esters in water, namely sucrose octanoate, sucrose decanoate, sucrose laurate, sucrose dodec-5- cis-enoate, sucrose myristate, and sucrose palmitate, has been investigated by means of two NMR methods, pulsed field gradient spin-echo NMR (PFGSE–NMR), giving access to the self-diffusion coefficients of free molecules and micelles in solution, and the ERETIC method (electronic reference to access in vivo concentrations) for the measurement of concentrations by external calibration of a synthetic NMR signal. The early micellar regions and, when possible, the premicellar regions were investigated. By this method, we obtained the hydrodynamic radii of micelles, displaying a linear progression in relation to the chain length and an accurate determination of critical micellar concentration (CMC) for each sucrose ester. The effect of the regiochemistry of fatty chain grafting has been investigated, showing special behavior for 1 ′ - O-sucrose palmitate.

Spontaneous Polymerization of N-(3-Dimethylaminopropyl)methacrylamide Salts in Concentrated Aqueous Solutions

Spontaneous polymerization of N-(3-dimethylaminopropyl)methacrylamide in concentrated aqueous solutions in the presence of inorganic and organic acids was studied. A common mechanism of initiation of spontaneous polymerization of amine-containing (meth)acrylamides and (meth)acrylic acid esters in water was suggested.

Micelle Catalyzed Hydrolysis of Carboxylic Acid Esters in Water–β‐Cyclodextrin–Cetyltrimethylammonium Bromide Systems

The micelle catalyzed hydrolysis of p‐nitrophenyl picolinate (PNPP) and p‐nitrophenyl acetate (PNPA) in water/β‐cyclodextrin (β‐CD)/cetyltrimethylammonium bromide (CTAB) systems were investigated spectrophotometrically at pH 7.02, 25°C. The pseudophase model for micellar catalysis was exployed to quantitatively treat the results obtained. Comparison of the results indicates that neither β‐CD nor the β‐CD complex form part of the micelles, the aggregation number being the same whether the micelles are in the presence or in the absence of the β‐CD and/or the β‐CD complex.

Development of a solid-phase microextraction method for the determination of phthalic acid esters in water

Solid-phase microextraction method (SPME) coupled to GC/ECD has been developed and validated for the determination of phthalic acid esters (dimethyl-, diethyl-, di- n-butyl-, butylbenzyl-, di-2-ethylhexyl- and di- n-octyl phthalate) in water samples. Two types of coatings (PDMS, PA), altogether four different kinds of fibers have been investigated. Both parameters affecting the partition of analytes between a fiber coating and aqueous phase (i.e. extraction time, extraction temperature, agitation) and conditions of the thermal desorption in a GC injector were optimized. The final SPME method employing the polyacrylate fiber, extraction time 20 min, heating and stirring of the sample enabled the determination of all six phthalates in water samples. The method showed linear response over four orders of magnitude and the limits of quantification of the method ranged between 0.001 and 0.050 μg l −1. The repeatability expressed as R.S.D. was in the range 4–10% for the spiking level 7 μg l −1 of each analyte. The applicability of the developed SPME method was demonstrated for real water samples.

A new receptor molecule for lysine and histidine in water: strong binding of basic amino acid esters by a macrocyclic host.

We present the new host molecule 1 which binds basic amino acid esters in water. It recognizes both positively charged groups of the amino acid esters by electrostatic and hydrogen bond interactions with its four strategically placed phosphonate anions. Selectivity for lysine is achieved by the correct distance between both bisphosphonate pairs. By contrast, the smaller amino acid esters arginine, ornithine, and histidine form 2:1 complexes with 1. In methanol, a double chelate assembly enforced by pi-cation interactions with the imidazolium cation leads to a very high association constant for the 1:histidine complex of 3 x 10(4) M(-)(1).

Reaction Pathways and Energy Barriers for Alkaline Hydrolysis of Carboxylic Acid Esters in Water Studied by a Hybrid Supermolecule-Polarizable Continuum Approach

Reaction pathways, solvent effects, and energy barriers have been determined for the base-catalyzed hydrolysis of two representative alkyl esters in aqueous solution, using a hybrid supermolecule-polarizable continuum approach. Four solvent water molecules were explicitly included in the supermolecular reaction coordinate calculations; the remaining solvent water was modeled as a polarizable dielectric continuum surrounding the supermolecular reaction system. Two competing reaction pathways were observed, sharing a common first step, i.e. the formation of the tetrahedral intermediate. One pathway involves a direct proton transfer in the second step, i.e. the decomposition of the tetrahedral intermediate. A second pathway involves a water-assisted proton transfer during the decomposition of the tetrahedral intermediate. The direct participation of the solvent water molecule in the proton-transfer process significantly drops the energy barrier for the decomposition of the tetrahedral intermediate. Thus, the...

Determination of Phthalic and Phosphoric Acid Esters in Water with Used of Solid Phase Extraction

Solid-phase microextraction (SPME) with six different non-polar and polar fibres was used to extract seven phthalate esters from water samples for analysis by gas chromatography–mass spectrometry. With regard to extraction efficiency and repeatability of the extractions, the 70-μm Carbowax–divinylbenzene fibre was especially suitable for the selected phthalates with water solubilities between 4200 mg l−1 (dimethyl phthalate) and 0.0003 mg l−1 (di-n-octyl phthalate). Linearity was controlled in the range between 0.02 and 10 μg l−1. In analysed drinking water samples from Leipzig (Germany) and Katowice (Poland) four of the investigated phthalates [diethyl phthalate, di-n-butyl phthalate, butylbenzyl phthalate and di(2-ethylhexyl) phthalate] were found to be present in concentrations between 0.02 and 0.6 μg l−1.

Determination of phthalic and phosphoric acid esters in water with used of solid phase extraction

Determination of phthalic and phosphoric acid esters in water with used of solid phase extraction