Carbon Tetrachloride Solution Research Articles

Determination of phthalate esters in cleaning and personal care products by dispersive liquid–liquid microextraction and liquid chromatography–tandem mass spectrometry

Phthalic acid esters (PEs) were preconcentrated from cleaning products, detergents and cosmetics using ultrasound assisted extraction (UAE) in the presence of acetonitrile, and then submitted to dispersive liquid–liquid microextraction (DLLME). For DLLME, 3mL of acetonitrile extract, 150μL carbon tetrachloride and 10mL aqueous solution were used. The enriched organic phase was evaporated, reconstituted with 25μL acetonitrile and injected into a liquid chromatograph with a mobile phase (acetonitrile:10mM ammonium acetate, pH 4) under gradient elution. Detection was carried out using both diode-array (DAD) and electrospray-ion trap-tandem mass spectrometry (ESI-IT-MS/MS) in the multiple reaction monitoring mode (MRM) of the positive fragment ions. Quantification was carried out using matrix-matched standards. Detection limits were in the range 0.04–0.45ngmL−1 for the six PEs considered. The recoveries obtained were in the 84–124% range, with RSDs lower than 10%. Thirty three different cleaning products were analyzed. The most frequently found compound was diethyl phthalate.

Association/Hydrogen Bonding of Acetone in Polar and Non-polar Solvents: NMR and NIR Spectroscopic Investigations with Chemometrics

This paper reports 1H NMR and NIR spectroscopic analysis of hydrogen bonding in acetone mixtures with water, CHCl3, CCl4, and CDCl3 with varying acetone concentrations (0–100 vol%). Spectroscopic data were chemometrically analyzed using independent component analysis to resolve the spectra of complexes existing in the solutions and to obtain their concentration profiles. Ab initio calculations provided additional information (hydrogen-bond energy and bond distance) about the investigated complexes. We have found that in addition to independent solvent associates, acetone–water mixtures contain three intermolecular complexes with acetone–water ratios of 1:1, 1:2 and 1:3. In less polar solvents with hydrogen or deuterium atoms (CDCl3, CHCl3), acetone does not generate self-associates and forms an intermolecular complex (1:1). In contrast, in aprotic non-polar carbon tetrachloride (CCl4) solutions, where no hydrogen-bonding is possible, self-association (as mentioned above for water–acetone mixtures) of two acetone molecules is preferred. The combination of spectroscopic techniques (1H NMR, NIR) with chemometric modeling and ab initio calculations leads to a better understanding of concentration dependent changes in the structure of acetone solutions. The approach discussed can be used for investigation of hydrogen-bonded interactions in other mixed solvents.

Feasibility of corona discharge ion mobility spectrometry for direct analysis of samples extracted by dispersive liquid–liquid microextraction

The capability of corona discharge ionization ion mobility spectrometry (CD-IMS) for direct analysis of the samples extracted by dispersive liquid–liquid microextraction (DLLME) was investigated and evaluated, for the first time. To that end, an appropriate new injection port was designed and constructed, resulting in possibility of direct injection of the known sample volume, without tedious sample preparation steps (e.g. derivatization, solvent evaporation, and re-solving in another solvent…). Malathion as a test compound was extracted from different matrices by a rapid and convenient DLLME method. The positive ion mobility spectra of the extracted malathion were obtained after direct injection of carbon tetrachloride or methanol solutions. The analyte responses were compared and the statistical results revealed the feasibility of direct analysis of the extracted samples in carbon tetrachloride, resulting in a convenient methodology. The coupled method of DLLME-CD-IMS was exhaustively validated in terms of sensitivity, dynamic range, recovery, and enrichment factor. Finally, various real samples of apple, river and underground water were analyzed, all verifying the feasibility and success of the proposed method for the easy extraction of the analyte using DLLME separation before the direct analysis by CD-IMS.

Capillary liquid chromatography combined with pressurized liquid extraction and dispersive liquid–liquid microextraction for the determination of vitamin E in cosmetic products

Capillary liquid chromatography (LC) is used for the determination of tocopherols and tocotrienols in cosmetic products. Dispersive liquid–liquid microextraction (DLLME) allows the analytes to be preconcentrated into a very small volume of organic solvent which is then injected into the chromatograph running at a very low flow rate. Pressurized liquid extraction (PLE) at a high temperature and pressure was used to isolate vitamin E forms from cosmetics. The Taguchi experimental method was used to optimize the factors affecting DLLME. The parameters selected were 2mL of acetonitrile (disperser solvent), 100μL carbon tetrachloride (extraction solvent) and 10mL aqueous solution. A volume of 5μL of the organic phase was injected into the reversed-phase capillary LC system equipped with a diode array detector and using an isocratic mobile phase composed of an 95:5 (v/v) methanol:water mixture at a flow-rate of 20μLmin−1. Quantification was carried out using aqueous standards and detection limits were in the range 0.1–0.5ngmL−1, corresponding to 3–15ngg−1 in the cosmetic sample. The recoveries were in the 87–105% range, with RSDs lower than 7.8%. The method was validated according to international guidelines and using a certified reference material.

Morphological features of C60 and C70 microcrystals obtained from C6H5CH3 and CCl4 solutions

Fullerene C60 and C70 microcrystals of different morphologies obtained by crystallization from toluene and carbon tetrachloride solutions were investigated using scanning electron microscopy and diffuse reflectance IR Fourier transform spectroscopy. The obtained results are discussed with regard to the features of fullerenes clusterization processes in solutions.

Estimation of Molecular Diffusivity in Liquid Phase Systems on the Basis of the Absolute Rate Theory

This study was concerned about an estimation of molecular diffusivity (D(m)) in liquid phase systems. An equation based on the absolute rate theory of diffusion was derived by considering the aggregation of not only solvent molecules, but also solute molecules. It was also studied how the replacement of the molar volume of a solvent with its molecular weight influences the accuracy in estimating D(m). The values of D(m) estimated by the equation were compared with those experimentally measured. The mean square deviation for the estimation of D(m) was calculated as being about 14% for 217 D(m) data measured in aqueous solutions of methanol and acetonitrile, which is comparable to that obtained by the Wilke-Chang equation. However, Dm of some solutes in carbon tetrachloride was more accurately estimated by this equation than by the Wilke-Chang equation. It is expected that the equation proposed in this study is effective for estimating D(m) in liquid phase systems.

ChemInform Abstract: Ferrous Salt Promoted Homocoupling of Arenediazonium Tetrafluoroborates under Mild Conditions.

AbstractThe method allows a simple and efficient preparation of symmetrical biaryls.

Adsorption of Aqueous Carbon Tetrachloride by a Novel TCAS-Loaded Resin

Through the method of the static tests, the removal rate of aqueous carbon tetrachloride onto a new TCAS-loaded resin was researched. This TCAS-loaded resin was made of a novel supramolecular acceptor compound named thiacalix [arenetetrasulfonate (TCAS) and anion exchange resin, and the adsorption mechanism was discussed preliminarily. The results of adsorption indicated that the pH value was an important factor for the removal of carbon tetrachloride and it would be better for the adsorption if the pH value was greater than 6. The operating temperature should be controlled in 5 to 15°C for the adsorption of carbon tetrachloride onto TCAS-loaded resin while the removal rate decreased with the temperature increasing and the best time for reaction was 40min. The removal rate of carbon tetrachloride in aqueous solution was better when 25mL aqueous solution of carbon tetrachloride (1.0mg/L) was adsorbed by 0.5g TCAS-loaded resin. The carbon tetrachloride can be resolving and TCAS-loaded resin can be reused.

On the Azo/Hydrazo Equilibrium in Sudan I Azo Dye Derivatives

In this study, Raman, infrared, UV/vis, NMR, and single crystal X-ray diffraction spectroscopies are used to elucidate the tautomeric equilibrium of azo dyes derived from 1-phenyl-azo-2-naphthol (Sudan I). A new crystallographic structure is described for Sudan I, revealing the presence of intramolecular hydrogen bonds and supramolecular interactions, such as the unconventional C-H···O hydrogen bond type, π-stacking, and charge-dipole interactions. All of these weak intermolecular interactions play a role in the stability of the crystalline structure. Theoretical calculations are also reported for geometries, energy, and spectroscopic properties. The predicted spectra are in accordance with the experiments carried out in the solid state and in solution of dichloromethane, carbon tetrachloride, and chloroform, suggesting the hydrazo form as the preferable tautomer in gas and condensate phases for Sudan I and its derivatives.

Fe(II)-Catalysed Homocoupling of Arenediazonium Tetrafluoroborates

An efficient procedure for the synthesis of biaryls was catalysed by Fe(acac)2 and zinc powder in carbon tetrachloride solution at 60 °C using arenediazonium salts is reported. Symmetrical bi-aryl molecules with various substituents on the phenyl ring (methyl, trifluoromethyl, halogen, nitro, methoxyl) were synthesised in good yields in a short time under air. Zinc powder was used as reductant in the reaction to facilitate the regeneration of the iron(II) catalyst.

FTIR spectroscopic study of hydrogen bonding and solvent induced frequency shifts of N-tert-butylacetamide

This paper reports the results of FTIR study of N-tert-butylacetamide in carbon tetrachloride solution and in presence of seven different molecules as H acceptors. The spectroscopic characteristics for NH⋯O hydrogen bonded complexes are given. Also, the equilibrium constants for 1:1 complex formation, at 25°C were determined by using IR measurements. Frequency shifts of carbonyl stretching vibration ν(CO) of N-tert-butylacetamide in the same organic H acceptors was also investigated. The wavenumbers of carbonyl stretching vibration ν(CO) were correlated with the solvent acceptor number (AN) and the linear solvation energy relationships (LSERs).

Ferrous salt-promoted homocoupling of arenediazonium tetrafluoroborates under mild conditions

A simple and efficient protocol has been developed for the synthesis of various symmetrical biaryls in good to excellent yields from the homocoupling reactions of arenediazonium salts with ferrous salt in carbon tetrachloride solution under mild reaction conditions. Moreover, the novel homocoupling has been demonstrated to proceed via an electron transfer reaction mechanism.

The effect of an anti-hydrogen bond on Fermi resonance: A Raman spectroscopic study of the Fermi doublet ν1−ν12 of liquid pyridine

The effects of an anti-hydrogen bond on the ν1−ν12 Fermi resonance (FR) of pyridine are experimentally investigated by using Raman scattering spectroscopy. Three systems, pyridine/water, pyridine/formamide, and pyridine/carbon tetrachloride, provide varying degrees of strength for the diluent-pyridine anti-hydrogen bond complex. Water forms a stronger anti-hydrogen bond with pyridine than with formamide, and in the case of adding non-polar solvent carbon tetrachloride, which is neither a hydrogen bond donor nor an acceptor and incapable of forming a hydrogen bond with pyridine, the intermolecular distance of pyridine will increase and the interaction of pyridine molecules will reduce. The dilution studies are performed on the three systems. Comparing with the values of the Fermi coupling coefficient W of the ring breathing mode ν1 and triangle mode ν12 of pyridine at different volume concentrations, which are calculated according to the Bertran equations, in three systems, we find that the solution with the strongest anti-hydrogen bond, water, shows the fastest change in the ν1−ν12 Fermi coupling coefficient W with the volume concentration varying, followed by the formamide and carbon tetrachloride solutions. These results suggest that the stronger anti-hydrogen bond-forming effect will cause a greater reduction in the strength of the ν1−ν12 FR of pyridine. According to the mechanism of the formation of an anti-hydrogen bond in the complexes and the FR theory, a qualitative explanation for the anti-hydrogen bond effect in reducing the strength of the ν1−ν12 FR of pyridine is given.

State of adsorption layers of fatty acids on the surfaces of iron, manganese, and copper ferrites

States of adsorbed substances in surface layers arising during the adsorption of oleic, linoleic, and linolenic acids from carbon tetrachloride, heptane, and cyclohexane solutions on the surfaces of iron, manganese, and copper ferrites, are investigated. Adsorption isotherms and two-dimensional state diagrams of surface layers of iron, manganese, and copper ferrites are obtained experimentally. It is shown that the adsorption of fatty acids from solutions in organic solvents proceeds via filling the volume of the ferrites’ porous space with adsorption solutions, while the state of ferrite surface layers changes due to the structural rearrangement of adsorption solutions upon an increase in solute concentration.

Electronic structures, intramolecular interactions, and aromaticity of substituted 1-(2-iminoethylidene) silan amine: a density functional study

The intramolecular hydrogen bond, molecular structure, π electrons delocalization, and vibrational frequencies in 1-(2-iminoethylidene) silan amine and its derivatives have been investigated by means of density functional method with 6-311++G** basis set, in gas phase, water, and carbon tetrachloride solutions. The obtained results showed that the hydrogen bond strength is mainly governed by resonance variations inside the chelate ring induced by the substituent groups. Furthermore, the topological properties of the electron density distributions for N–H···N intramolecular hydrogen bond were analyzed in terms of the Bader's theory of atoms in molecules. On the other hand, the aromaticity of the ring formed is measured using several well-established indices of aromaticity such as nucleus-independent chemical shift, harmonic oscillator models of the aromaticity, para-delocalization index, average two-center indices, aromatic fluctuation index, and π-fluctuation aromatic index. Natural population analysis data, the electron density and Laplacian properties, as well as γ(NH) and ν(NH) were further used for estimation of the hydrogen bonding interactions and the forces driving their formation.

Adsorption isotherms of linoleic and linolenic acids from solutions in carbon tetrachloride on surfaces of highly dispersed manganese and copper ferrites

A comparative study of adsorption-desorption isotherms of linoleic and linolenic acids from solutions in carbon tetrachloride on surfaces of manganese and copper ferrites is performed by means of equilibrium adsorption. Adsorption isotherms of fatty acids are described in terms of the theory of volume filling of micropores, and the values of the limiting adsorption, the characteristic adsorption energy, and the pore space volume are calculated. It is established that the limiting adsorption values of linoleic and linolenic acids from solutions in carbon tetrachloride on a copper ferrite surface are higher than on a manganese ferrite surface. It is shown that the adsorption-desorption isotherms have a hysteresis loop.

Two-dimensional infrared (2D IR) correlation spectroscopy study of self-assembly of oleic acid (OA) in conjunction with partial attenuation of dominant factor by eigenvalue manipulating transformation (EMT)

Highly selective two-dimensional (2D) correlation analysis, achieved by attenuating a major principal component in spectral data with eigenvector manipulating transformation (EMT) technique, was demonstrated. A spontaneous evaporation process of a binary mixture solution of oleic acid (OA) and carbon tetrachloride (CCl4) was monitored by attenuated total reflection infrared (ATR-IR) spectroscopy. Fine details of the dynamic behavior of OA molecules undergoing self-assembly into smectic liquid crystals were analyzed by 2D correlation spectroscopy scheme in conjunction with EMT technique. Correlation feature derived from the original spectral data is dominated with the contribution from the major dimer components of OA. On the other hand, 2D correlation spectra generated form the reconstructed data by attenuating the first principal component (PC1) showed selective enhancement of the correlational feature associated with the minor monomer component, which makes it possible to identify distinct populations, each having different dynamic behavior during the self-assembly.

Impairment of α<sub>2</sub>-Macroglobulin Synthesis in Experimental Hepatopathic Rats Treated with Turpentine Oil

The aim of this study was to investigate the synthesis of α(2)-macroglobulin (α2M) in hepatopathic rats injected with turpentine oil to induce acute inflammation. Hepatopathy was induced by oral administration of acetaminophen at a dose of 1 g/kg daily for 2 weeks or a 25% solution of carbon tetrachloride (CCl(4)) at 2 ml/kg body weight three times per week for 7 weeks. Acute inflammation was induced by intramuscular injection of turpentine oil at a dose of 1.0 ml/kg body weight. Serum concentrations of α2M were measured by enzyme-linked immunosorbent assay. Aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase and total protein differed significantly between acetaminophen or CCl(4)-induced hepatopathic rats and acetaminophen control (AA-control) or CCl(4) control (CC-control) rats. Furthermore, pathological examination confirmed hepatopathy in rat livers. Peak serum concentrations and area under the time-concentration curve for α2M showed significant differences between hepatopathic rats and AA-control or CC-control rats. Thus, serum concentrations of α2M did not increase when compared with nontreated rats.

EXPERIMENTAL MODELING OF TOXIC HEPATIC INJURY

Objective: to perfect in experiment models of acute and chronic toxic injuries of liver, to evaluate possibilities of their application to study the processes of liver regeneration and its correction. Materials and methods: white male rats Vistar; intraperitoneal injection of 50 % solution of carbon tetrachloride made on olive oil; intragastric introduction of acetaminophen; morphological and morphometrical methods. Results. The models of toxic hepatitis and hepatic cirrhosis were received in experiment. Hepatic cirrhosis is postnecrotic and mainly multilobular. Conclusion. The carbon tetrachloride model of toxic hepatitis and cirrhosis can be used for reproduction of this pathology in experiment. However it is not optimal as the sensitivity of rats to carbon tetrachloride differs and the changes in liver have reversible character after the preparation cancellation.

Use of Solution-Phase Vibrational Frequencies in Continuum Models for the Free Energy of Solvation

We find that vibrational contributions to a solute's free energy are in general insensitive to whether the solute vibrational frequencies are computed in the gas phase or in solution. In most cases, the difference is smaller than the intrinsic error in solvation free energies associated with the continuum approximation to solvation modeling, although care must be taken to avoid spurious results associated with limitations in the quantum-mechanical harmonic-oscillator approximation for very low-frequency molecular vibrations. We compute solute vibrational partition functions in aqueous and carbon tetrachloride solution and compare them to gas-phase molecular partition functions computed with the same level of theory and the same quasiharmonic approximation for the diverse and extensive set of molecules and ions included in the training set of the SMD continuum solvation model, and we find mean unsigned differences in vibrational contributions to the solute free energy of only about 0.2 kcal/mol. On the basis of these results and a review of the theory, we conclude, in contrast to previous work (Ho, J.; Klamt, H.; Coote, M. L. J. Phys. Chem. A 2010, 114, 13442), that using partition functions computed for molecules optimized in solution is a correct and useful approach for averaging over solute degrees of freedom when computing free energies of solutes in solution, and it is moreover recommended for cases where liquid and gas-phase solute structures differ appreciably or when stationary points present in liquid solution do not exist in the gas phase, for which we provide some examples. When gas-phase and solution-phase geometries and frequencies are similar, the use of gas-phase geometries and frequencies is a useful approximation.