Sustainable and green microextraction of organophosphorus flame retardants by a novel phosphonium‐based deep eutectic solvent

Based on the solidification of a hydrophobic deep eutectic solvent in air‐assisted liquid phase microextraction combined with gas chromatography and mass spectrometry, a green and sustainable microextraction technique was developed for extracting, separating, and detecting organophosphorus flame retardants in aqueous samples. In this study, some strategies were considered for overcoming or improving the challenges of conventional solvent microextraction procedures. In addition, a hydrophobic deep eutectic solvent with a freezing point near the ambient temperature was employed as an extraction phase, the dispersive solvent was substituted by the syringe pump process, and the centrifugation step was omitted by using salting‐out phenomenon. Further, the effect of the main independent variables was evaluated by using the chemometric methods in order to maximize the extraction efficiency of the procedure. Under optimal conditions, the calibration model was linear in the range of 0.01–25.0 µg/L. Limits of detection and quantitation were assessed at the concentration levels of 2–23 and 9–65 ng/L, respectively. The precision involving repeatability and reproducibility was evaluated by estimating the relative standard deviation, the levels of which were <6.6 and <8.7%, respectively. The applicability of the method was successfully evaluated by analyzing the target analytes in real aqueous samples, which illustrated satisfactory recoveries (95–104.61%).     

A new ab initio ground-state dipole moment surface for the water molecule

A valence-only (V) dipole moment surface (DMS) has been computed for water at the internally contracted multireference configuration interaction level using the extended atom-centered correlation-consistent Gaussian basis set aug-cc-pV6Z. Small corrections to these dipole values, resulting from core correlation (C) and relativistic (R) effects, have also been computed and added to the V surface. The resulting DMS surface is hence called CVR. Interestingly, the C and R corrections cancel out each other almost completely over the whole grid of points investigated. The ground-state CVR dipole of H(2) (16)O is 1.8676 D. This value compares well with the best ab initio one determined in this study, 1.8539+/-0.0013 D, which in turn agrees well with the measured ground-state dipole moment of water, 1.8546(6) D. Line intensities computed with the help of the CVR DMS shows that the present DMS is highly similar to though slightly more accurate than the best previous DMS of water determined by Schwenke and Partridge [J. Chem. Phys. 113, 16 (2000)]. The influence of the precision of the rovibrational wave functions computed using different potential energy surfaces (PESs) has been investigated and proved to be small, due mostly to the small discrepancies between the best ab initio and empirical PESs of water. Several different measures to test the DMS of water are advanced. The seemingly most sensitive measure is the comparison between the ab initio line intensities and those measured by ultralong pathlength methods which are sensitive to very weak transitions.     

Supramolecular-based solvent microextraction of carbaryl in water samples followed by high performance liquid chromatography determination

In this study, a simple, rapid, low cost, sensitive and environmentally friendly technique, supramolecular solvent microextraction (SM-SME) followed by high performance liquid chromatography-ultraviolet has been proposed to extract carbaryl from water samples. Parameters, affecting the SM-SME performance such as the weight of decanoic acid (DeA), volume of tetrahydrofuran (THF), pH and salt concentration, were studied and optimised. The effect of the pH on the extraction efficiency was evaluated by one–factor-at-a-time methodology, but the other variables were optimised by a face-centred cube central composite design methodology. Optimum extraction conditions were obtained: DeA: 70 mg; THF: 650 µL; salt concentration: 10% (w/v) NaCl and pH = 2–4), and the performance of the proposed method was evaluated. Under the optimum conditions, good linearity (1.0–500 µg L^?1, r² = 0.9994) was obtained. Limit of detection and limit of quantification were 0.3–1.0 µg L^?1, respectively. Also, the recoveries of the carbaryl were obtained in the ranged from 96% to 105%. Finally, proposed method was successfully applied for the determination of the carbaryl in the water samples of farms run-off and rivers and satisfactory results were obtained.     

1,1,2,2-Tetrahydroperoxy-1,2-diphenylethane as new oxidant for chemoselective and catalyst free oxidation of sulfides to sulfoxides and sulfones

A catalyst free and chemoselective oxidation of sulfides to sulfoxides or sulfones was developed using 1,1,2,2-tetrahydroperoxy-1,2-diphenylethane as a new oxidant. This scope has shown the achievement of various sulfoxides and sulfones which were obtained selectively in high yields at room temperature.     

N‐Bromosuccinimide (NBS): A Novel and Efficient Catalyst for the Synthesis of 14‐Aryl‐14H‐dibenzo[a,j]xanthenes under Solvent‐Free Conditions

A novel procedure for the synthesis of 14‐aryl‐14H‐dibenzo[a,j]xanthenes through one‐pot condensation of naphthalen‐2‐ol with arenecarbaldehydes in the presence of N‐bromosuccinimide (NBS) as catalyst under solvent‐free conditions is described.     

Thermal response of dielectric,impedance and modulus spectroscopy study of NCZA bulk ceramics

The Ni_0.27Cu_0.10Zn_0.63Fe_1.96Al_0.04O₄ (NCZA) magnetic bulk ceramics is prepared via conventional solid state reaction technique. X-ray diffraction study has confirmed the single phase spinel crystal structure. The surface morphology has been studied and found small grain size distributions that are separated by well-defined grain boundaries. Besides, to understand the thermal and frequency variation of the electrical and dielectric properties, the investigation has done at different selected temperatures (T_m = 300, 323, 373, 423, 473, 523 and 573) over a range of frequency (20 Hz to 2 MHz) throughout a non-destructive impedance spectroscopy technique. It is observed that the dielectric constant has increased with the increase of T_m as well as frequency. The impedance plot showed two semicircular arcs due to the distinguishing relaxation time constant of charge carrier of grain and grain boundaries. Modulus spectroscopy has been carried out to analyze the mechanism of electrical transport process in the ceramics.     

Assessment of MRI issues for the Argus II retinal prosthesis

Objective

The objective was to evaluate magnetic resonance imaging (MRI) issues (magnetic field interactions, heating, artifacts and functional alterations) at 1.5 T and 3 T for the Argus II Retinal Prosthesis (Second Sight Medical Products, Sylmar, CA, USA).

Materials and Methods

Standardized protocols were used to assess magnetic field interactions (translational attraction and torque; 3 T, worst case), MRI-related heating (1.5 and 3 T), artifacts (3 T; worst case) and functional changes (1.5 and 3 T) associated with MRI.

Results

The magnetic field interactions were acceptable. MRI-related heating, which was studied at a relatively high, MR system-reported whole body averaged specific absorption rates, will not pose a hazard to the patient under the conditions used for testing. While artifacts were “moderate” in relation to the dimensions of the Argus II Retinal Prosthesis, optimization of MRI parameters can reduce the size of the artifacts. Exposures to MRI conditions at 1.5 and 3 T did not damage or alter the functional aspects of the Argus II Retinal Prosthesis.

Conclusions

In consideration of the test results, a patient with the Argus II Retinal Prosthesis may undergo MRI at 1.5 T or 3 T when specific guidelines and MRI conditions are followed, including those advised by the manufacturer.     

An upper-bound analysis for frictionless TCAP process

Tubular channel angular pressing (TCAP) process was proposed recently as a novel severe plastic deformation technique for producing ultrafine grain and nanostructured tubular components. In this paper, an upper-bound approach was used to analyze the TCAP process. Deformation of the material during TCAP process is analyzed using upper-bound analysis to determine maximum required load. The effects of TCAP parameters such as channel and curvature angles, deformation ratio (R ₁/R ₂) and tube material on the process pressure were investigated. The results showed that an increase in the second channel angle and decrease in the ratio R ₁/R ₂ lead to lower process loads. In the first and third curvature angles ranging from 25 to 65°, the required load remains almost constant. The apparent punch load decrease when hardening exponent n is increased. To verify the theoretical results, the finite element (FE) modeling was employed. Good agreement was observed between the predicted pressure from upper-bound analysis and FE results.     

Volumetric properties and viscosities of the 2-pyrrolidone + 1,2-propanediol + water ternary system and its binary constituents at T = 313.15 K

Densities and viscosities of ternary mixtures of 2-pyrrolidone + 1,2-propanediol + water and corresponding binary mixtures of 1,2-propanediol + water, 2-pyrrolidone + water and 2-pyrrolidone + 1,2-propanediol have been measured over the whole composition range at 313.15 K. From the obtained data, the excess molar volumes (V^E), the deviations in viscosity (Δη) and the excess Gibbs free energy of activation (ΔG^?E) have been calculated. The V^E, Δη and ΔG^?E results were correlated and fitted by the Redlich–Kister equation for binary mixtures and by the Cibulka equation for ternary mixtures, as a function of mole fraction. Several predictive empirical relations were applied to predict the excess molar volumes of ternary mixtures from the binary mixing data.     

On-line solid phase extraction coupled to ICP-OES for simultaneous preconcentration and determination of some transition elements

An on-line solid phase extraction method coupled to ICP-OES was developed for the simultaneous determination of Ce(III), La(III), Sm(III), Y(III), Yb(III), Dy(III), Hf(IV), Zr(IV) and Th(IV) ions in aqueous samples. The ions forming hydrophobic complexes with 3,5,7,2?,4?-pentahydroxy flavone (morin) and were retained on an octadecyl silica (C₁₈) minicolumn. The adsorbed chelates were subsequently eluted from the column and directly transferred into the plasma with 80% (v/v) propanol:H₂O solution for the simultaneous determination of the metal ions. Different parameters affecting the ICP-OES signal intensities and extraction efficiency including pH of the solution, concentration of the chelating agent, flow rate and type of the eluent, loading rate and ionic strength were evaluated and optimized. The calibration graphs were linear in the range of 0.2–100 μg L^?1 and limit of detections for the extraction and determination of the ions in the aqueous sample (25 mL) were in the range 0.10–0.46 μg L^?1. The enhancement factors of the method for the metal ions obtained were in the range of 23 to 242 (V _Sample?=?25 mL) and the precision expressed as relative standard deviations (RSD %) was below 6.9%. Finally, the method was successfully applied to determine the target analytes in natural water samples.