Presence Of Other Solvents Research Articles

Turn-on fluorimetric sensor for water dispersed volatile organic compounds - A nanosponge approach

Herein we introduce a concept of nanoparticles based, turn-on, fluorimetric approach for sensitive, fast, reversible sensing of low concentrations of volatile organic compounds (VOCs), such as xylene, dispersed in a solution with detection limit as low as 7 ppm achieved without preconcentration. Spontaneous partitioning of VOC to stable, crosslinked polymeric nanoparticles results in nanocapsule formation and change of optical spectra of the dye contained in the nanostructure. For polythiophenes used as dyes, capsule formation results in pronounced increase in diameter and emission increase due to change in form of polymer-dye in the nanostructures: from aggregates of low emission to a dispersed phase of high emission observed at wavelength typical for a dispersed polymer. The selectivity of the native system results from affinity of VOC analyte to polythiophene and nanoparticle material, resulting in xylene selectivity. Increase of the emission signal was observed for xylene concentrations 60 or 120 ppm, depending on the amount of the dye introduced into the nanostructure. Uncommonly for many sensors, in the presence of other solvents lowering of the detection limit was observed and a linear dependence of emission intensity on xylene concentration was obtained. It is shown that using nanosponges pretreated with chloroform a linear dependence of emission in turn on mode is observed within the range from 0 to 200 ppm, with detection limit as low as a few ppm. The proposed novel and original approach is applicable for extending to different nanoparticle materials and dyes combinations, thus sensitivity of the system can be tuned according to needs.

Dimethyl phthalate. Determination in workplace air

Dimethyl phthalate (DMP) is a colourless liquid with a slight aromatic odour. It is used in industry as a plasticizer of plastics, as an ingredient of fragrances in the production of cosmetics and detergents. Occupational exposure to DMP can occur through inhalation, or ingestion. The aim of this study was to validate a method for determining DMP concentration in workplace air in the range from 1/10 to 2 MAC values, in accordance with the requirements of standard PN-EN 482. The study was performed using a gas chromatograph (GC) with a flame ionization detector (FID) equipped with a capillary column HP-INNOWAX (60 m x 0.25 mm, 0.15 µm). This method is based on the sorption of dimethyl phthalate vapours on a glass microfiber filter, desorption with ethanol, and analyzed by GC-FID. The average desorption efficiency of DMP from filter was 98%. Application of HP-INNOWAX column allows selective determination of DMP in the presence of other solvents. The measurement range was 0.5 – 10 mg/m3 for a 120-L air sample. Limit of detection: 0.02 µg/ml and limit of quantification: 0.06 µg/ml. The analytical method described in this paper enables a selective determination of DMP in workplace air in the presence of other solvents at concentrations from 0.5 mg/m3 (1/10 MAC value). The method is characterized by good precision and accuracy and meets the criteria for the performance of procedures for the measurement of chemical agents, listed in EN 482. The method may be used for the assessment of occupational exposure to DMP and the associated risk to workers’ health. The developed method of determining DMP has been recorded as an analytical procedure (see appendix). This article discusses the problems of occupational safety and health, which are covered by health sciences and environmental engineering.

Methanol-enhanced degradation of carbon tetrachloride by alkaline activation of persulfate: Kinetic model

Carbon tetrachloride (CT), a chlorinated organic compound widely used in the chemical industry during the 20th century, is nowadays a ubiquitous contaminant in groundwater and in situ technologies for its destruction are required. In this work, the degradation of CT by the alkaline activation of persulfate (PS) has been studied. Among the pool of radical species generated (hydroxyl radicals, sulfate radicals and superoxide radicals), O2∙− resulted to be the only species responsible for CT abatement. It has been found that the presence of other solvents less polar than water (hydrogen peroxide, acetone, propanol and methanol) improves CT degradation. Among them, methanol was selected as the most adequate co-solvent, leading to the complete elimination of CT (100 mg L−1, 24 h) with a moderate unproductive consumption of the oxidant. The degradation of CT increased proportionally with the concentration of this solvent (from 0.1 to 10 g L−1). The ratio NaOH:PS (from 1 to 8) did not affect the degradation of CT when working with a constant concentration of PS and highly alkaline conditions were maintained. The removal rate of CT increased as the concentration of PS increased (from 20 to 60 g L−1), while the conversion of this pollutant did not depend on its initial concentration (from 10 to 100 mg L−1). A kinetic model that considers the concentration of PS, MeOH and CT and can predict the concentration of CT with reaction time at different operating conditions, has been developed from the experimental data.

Supercritical CO2 utilization for the crystallization of 2D metal-organic frameworks using tert-butylpyridine additive

Recently, the study of the synthesis of metal-organic frameworks (MOFs) in the presence of supercritical CO2 (scCO2) has become a burgeoning direction in materials science. MOFs crystallization in scCO2 is often carried out in the presence of other solvents, such as ionic or organic liquids, to increase reagents solubility in the reaction media. In this work, a totally new and cleaner way is followed, utilizing small amounts of an ancillary ligand to increase metal solubility, which result in a more efficient use of scCO2. The precipitation of 2D MOFs, based in the combination of different trifluoroacetates of transition metals (M(tfa)2, MII = CuII or ZnII), and a bidentate pyridine derivative (dpy), was studied. MOFs of the type [M(tfa)2(dpy)x]∝ were precipitated using scCO2 as the solvent medium and the ligand tert-butylpyridine (t-bpy) as additive. The targeted 2D MOFs were precipitated after a short reaction time (ca. 3 h) operating under relatively soft supercritical conditions (20 MPa and 333 K). This new synthetic approach is thought as a generic method that can be used to modify metal precursors in systems in which the reaction is too slow or incomplete in neat scCO2. Moreover, the increase of metal centre solubility allowed the in situ deposition of MOF crystals grafted on modified substrates.

Deep eutectic-water binary solvent associations investigated by vibrational spectroscopy and chemometrics.

Investigation of the behaviour of deep eutectic solvents (DESs) as novel green solvents in the presence of other solvents is of great interest. In this study the behaviour of a common natural DES, namely choline chloride-glycerol deep eutectic solvent (GDES), was studied in the presence of water. A detailed study of the association of the two solvents was performed by integration of two vibrational spectroscopic methods (FTIR and Raman spectroscopy) followed by multivariate analysis. Moreover, a binary mixture of glycerol (Gly) as one of the liquid constituents of GDES and water was explored under the same conditions. A quintuplet and ternary systems were resolved for GDES-water and Gly-water probes, respectively, using multivariate analysis of global data (multi-technique and multi-experiment data arrangements). The results confirmed that in the presence of water the GDES showed different behaviour from its components. Therefore, a DES can be introduced as an independent solvent with its unique properties. Also, different H-bond interaction energies of GDES and its pure components in the presence of water were shown by theoretical calculations based on a density functional theory framework. To investigate the effects of water on the structure of GDES, molecular dynamics (MD) simulations of GDES-water liquid mixtures were performed at 0.9 mole fraction of water.

Diethyl phthalate Determination in workplace air

Diethyl phthalate (DEP) is an ester of phthalic acid and an ethanol. It is a colorless, oily liquid. This substance is used in industry as a solvent for cellulose acetate and nitrocellulose, and a plasticizer of plastics. It is added to nail polish, perfumes in cosmetics and detergents, food packaging and pharmaceuticals. Diethyl phthalate is a substance which is toxic if inhaled, irritating to eyes and skin, toxic for reproduction (it is suspected that acts harmful to fertility or unborn child). The aim of this study was to develop and validate a method for determining concentrations of diethyl phthalate in workplace air in the range from 1/10 to 2 MAC values in accordance with the requirements of Standard No. PN-EN 482. The study was performed using a gas chromatograph (GC) with a flame ionization detector (FID) with a capillary column HP-INNOWAX (60 m × 0.25 mm, 0.15 µm). The method is based on the adsorption of diethyl phthalate on glass microfiber filter, desorption of analysed compound with ethanol and analysis of the resulting solution with GC-FID. The average desorption efficiency of diethyl phthalate from filter was 90%. Application of column HP-INNOWAX enables selective determination of diethyl phthalate in the presence of other solvents. The measurement range was 0.3  6 mg/m3 for a 240-L air sample. The limit of detection (LOD) and the limit of quantification (LOQ) are 0.09 µg/ml and 0.27 µg/ml, respectively. The analytical method described in this paper enables selective determination of inhalable fraction of diethyl phthalate in workplace air in the presence of other substances at concentrations from 0.3 mg/m3 (1/10 MAC value). The method is precise, accurate and it meets the criteria for procedures for measuring chemical agents listed in Standard No. EN 482. The method can be used for assessing occupational exposure to diethyl phthalate and associated risk to workers’ health. The developed method of determining diethyl phthalate has been recorded as an analytical procedure (see appendix).

Prediction of diffusion in a ternary solvent–solvent–polymer blend by means of binary diffusion data: Comparison of experimental data and simulative results

ABSTRACTMulticomponent diffusion of solvents in polymeric systems is not completely understood, despite many scientific contributions to the topic. Literature scarcely offers measurement data on diffusion for model validation in such systems. In this work, the ternary systems consisting of poly(vinyl acetate) and the solvents toluene and methanol was investigated experimentally and numerically. By means of inverse micro Raman spectroscopy (IMRS) concentration gradients in drying thin films have been measured. Initial composition of the samples has been varied systematically in order to detect mutual influence of the solvents' diffusive behavior. It was shown that the mobility of the different species is increased in the presence of other solvents as predicted by theory. This experimental data is provided for model validation. A new expression to calculate the diffusion coefficients in ternary mixtures is proposed which only requires binary data. This expression is tested by means of a model‐based simulation to predict the drying of ternary polymer solutions in terms of concentration profiles and residual solvent content. The results are in very good agreement with the experiments. Cross terms diffusion coefficients and thermodynamic factors were not found to be necessary for a satisfying prediction. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43899.

Low level detection of Benzene in Food Grade Hexane by Ultraviolet Spectrophotometry

A simple, sensitive, and accurate Ultraviolet Spectrophotometric method has been developed and validated for the determination of Benzene in Food Grade Hexane. Benzene in spectroscopic grade Hexane shows vibrational fine structure having four well resolved peaks. In the wavelength range 240–270nm, peak at 255nm is considered for the method development. Beer’s law was obeyed in the concentration range of 0.6–10.0μLL−1, with correlation coefficient, 0.9999, detection limit 0.2μLL−1 and quantitation limit 0.6μLL−1 are established. Percentage recovery studies showed that the method was not affected by the presence of other solvents having the similar boiling range with Hexane. The method was validated by determining its accuracy and precision which proves suitability of the developed method for the routine determination of Benzene in Food Grade Hexane. The proposed method has been applied successfully for the analysis of the Food Grade Hexane.

Impact of coexposure on toluene biomarkers in rats

1. Toluene (TOL) is widely used in industry. Occupational exposure to TOL is commonly assessed using TOL in blood, hippuric acid and ortho-cresol. Levels of these biomarkers may depend on factors potentially interfering with TOL biotransformation, such as the presence of other solvents in the workplace. Mercapturic acids (MAs) could be an alternative to the “traditional” TOL biomarkers.2. This study aims (1) to investigate in rat the effects of an exposure to vapours mixtures on the TOL metabolism, and (2) to assess how well MAs performed in these contexts compared to the traditional TOL biomarkers.3. Rats were exposed by inhalation to binary mixtures of TOL with n-butanol (BuOH), ethyl acetate (EtAc), methyl ethyl ketone (MEK) or xylenes (XYLs); biological exposure indicators were then measured.4. Depending on the compounds in the mixture and their concentrations, TOL metabolism was accelerated (with BuOH), unchanged (with EtAc) or inhibited (with XYLs and MEK). Inhibition leads to an increase in blood TOL concentrations, even at authorized atmospheric concentrations, which may potentiate the effect of TOL.5. MAs excretions are little affected by coexposure scenarios, their levels correlating well with atmospheric TOL levels. They could thus be suitable bioindicators of atmospheric TOL exposure.

Extraction studies of plutonium from acidic solution using γ-ray induced PC-88A/TBP modified polymers

Ethylhexyl-2-ethylhexyl phosphonic acid (PC-88A) and Tributylphosphate (TBP) extractants have been attached to polypropylene (PP) in granular, film and non-woven fabric forms, by a simultaneous c-ray irradia- tion method. The extraction of plutonium from the acidic radioactive liquid waste by modified polymers was studied by varying the c-ray dose. The uptake of plutonium was also studied by polyethylene (PE) in film form. This modified polymer also showed extraction capability for plutonium from nitric acid medium. The uptake of pluto- nium depends upon the c-ray dose as well as the nature and source of the polymer. Liquid-solid extraction studies showed that the equivalent amount of uptake of plutonium on TBP-polyethylene film requires twice the c-ray dose as compare to TBP-polypropylene film. It was observed that at given c-ray dose polypropylene fabric is not sturdy, compare to the granules and films, and material leach out in aqueous phase. The presence of other solvents like di-methyl formamide (DMF) and cyclohexane during c-ray irradiation were able to enhance the extraction capabilities. The optimum conditions established during this study was successfully applied for the separation of plutonium, ura- nium and thorium from the fission products in acidic waste solution.

Thermal Stability of the Li ( Ni0.8Co0.15Al0.05 ) O2 Cathode in the Presence of Cell Components

The cathode, a potential candidate for hybrid electric vehicle applications, has been electrochemically charged in powder form without a carbon additive and binder. The thermal stability of the resulting powder was studied by thermal gravimetric analysis (TGA), gas chromatography/mass spectrometry, and X-ray diffraction techniques under different gas flows. The transformation of -layered material to the -type structure material and/or to nickel metal was correlated to the oxidizing/reducing properties of the TGA gas flow under which the thermal decomposition of the occurred. Differential scanning calorimetry measurements were performed on powder in the presence of solvent, salt, or binder independently. The reactivity at between and ethylene carbonate (EC) solvent was found to be dependent on the oxide/EC weight ratio. The exothermic reaction observed in the presence of other solvents was not greatly affected, as long as the oxide/solvent weight ratios were kept very close to one another. The salt, when added to the charged oxide powder, was found to shift the exothermic reaction to when it was dissolved in the electrolyte and when it was added in the solid form. When polyvinylidene fluoride binder was added to powder, the exothermic reaction occurred at high temperatures . The initiation of the exothermic reaction has been primarily attributed to the oxidation of the electrolyte by the oxygen gas released from after the collapse of its layered structure.

Pervaporation of toluene and toluene/acetone/ethyl acetate aqueous mixtures through dense composite polydimethylsiloxane membranes

The study was aimed at removing organic solvents from aqueous solutions using pervaporation. The tests were carried out on a composite polydimethylsiloxane (PDMS) membrane manufactured by GKSS/ Forschungszentrum Geesthacht, Germany and a polydimethylsiloxane membrane filled with carbon black (PDMS+cb) prepared in a laboratory. There were two runs: the first one tested an aqueous toluene solution as feed, while the other used a mixture of solvents: toluene, acetone and ethyl acetate. It has been found that the PDMS membrane without carbon black removed all the components of the mixture, displaying a very high efficiency of the process. However, the selectivity and enrichment factors turned out to be relatively low. The PDMS+cb membrane produced slightly lower removal degrees as well as acetone and ethyl acetate fluxes compared to the PDMS membrane, yet their concentration at the permeate side of the membrane was considerably higher. It has also been observed that the presence of other solvents did not affect greatly toluene permeation - its final removal seemed to be independent of the composition of the feed used.

Effect of Eight Solvents on Ethanol Analysis by Draäger 7110 Evidential Breath Analyzer

The Dräger 7110 MK III FIN Evidential breath analyzer is classified as a quantitative analyzer capable to provide sufficient evidence for establishing legal intoxication. The purpose of this study was to evaluate ethanol specificity of this instrument in the presence of other solvents. Effects of eight possible interfering compounds on ethanol analysis were determined in a procedure simulating a human breathing. Most of the compounds studied had either a negligible effect on ethanol analysis (acetone, methyl ethyl ketone, and methyl isobutyl ketone) or were detected in very low concentrations before influencing ethanol readings (methanol, ethyl acetate, and diethyl ether). However, 1-propanol and 2-propanol increased the ethanol readings significantly. Thus, Dräger ethanol readings should be interpreted carefully in the presence of propanol.

Activity and stability of dextransucrase from Leuconostoc mesenteroides NRRL B-512F in the presence of organic solvents

The behavior of dextransucrase from Leuconostoc mesenteroides NRRL-B-512F in the presence of organic solvents was investigated. The activity and stability of this enzyme were studied in the presence of various concentrations (% v/v) of dimethysulfoxide (DMSO), dimethylformamide (DMF), ethanol, acetone and acetonitrile. The stability was measured at 4°C and 30°C. Generally the initial velocity of dextransucrase decreases proportionally to solvent concentrations except in water–DMSO mixture. Indeed in 25% DMSO (v/v), 45% of the activity in pure water was detected whereas 26% was measured in 10% DMSO (v/v). Moreover the loss of activity is much more considerable in the presence of acetonitrile than in the presence of other solvents. In 20% acetonitrile (v/v), only 11% of the activity was measured. Concerning the stability of the enzyme it appears that it is more stable at 4°C than at 30°C. Surprisingly dextransucrase is more active after a period of contact with some solvents, especially DMSO or ethanol, than in acetate buffer. After 2 days in 20% DMSO (v/v) at 4°C, 300% of the initial activity remained and 250% at 30°C. This increase of activity is also observable after 2 days in 20% ethanol (v/v) where 180% of the initial activity is measured.

Spectrophotometric determination of hypochlorite traces in basic solutions with the reagent 3, 3′-dimethylnaphtidine

A spectrophtometric method for the determination of hypochlorite traces in solutions containing 4 M NaOH based on the reaction of the reagent 3, 3′-dimethylnaphtidine (DMN) with chlorine is described. Use is made in common reagent containing DMN, hydrochloric acid, and dimethylformamide. This common reagent enables the liberation and determination of chlorine in situ in strongly acidic solutions. The effect of factors such as acidity, temperature, and the presence of other solvents, oxidation agents, and metallic impurities on the absorption spectrum has been studied. The factors affecting the chemical stability of the common reagent are discussed.