Extraction and Analysis of Carbamate and Pyrethroid Pesticides in Tomatoes and Rice by Gas Chromatography Mass Spectrometry

This work aimed to explore common methods for the extraction of pesticide and to perform qualitative and quantitative analysis by gas chromatography coupled with electron impact mass spectrometry (GC-EI-MS). Extraction was conducted using QuEChERS and Liquid-Liquid (L-L). Calibration curve and standard addition curve were both plotted for different concentration of mixtures. Additionally, the efficiency of the QuEChERS extraction methods was examined by spiking the organic rice and tomato with standard mixture of pyrethroid and carbamate and applying the extraction. Results showed that, in general, carbamate species (especially the aliphatic types) were eluted at earlier times compared to pyrethroids species. Carbamates were more susceptible to degradation during GC separation compared to pyrethroids. A chromatographic resolution of 3.24 was obtained for the two permethrin isomers. Good linearity of the three quantitative methods (R2 > 0.99) were obtained for most compounds. Based on using the standard addition curve, the recovery for the different pyrethroid and carbamate compounds were determined.qscienc

Synthesis and characterization of Eu3+ doped TiO2 thin films deposited by spray pyrolysis technique for photocatalytic application

In this study, nanocrystalline TiO _2 : Eu ^3+ thin films are successfully formed by spray pyrolysis technique deposited on glass substrate. Structure, optical, electrical, surface morphology, and photocatalytic degradation of Methylene blue have been examined. The XRD analysis illustrate the tetragonal crystal structure of films with anatase phase and reduces crystallite size linearly with increasing Eu ^3+ concentration. The optical properties of the films are analyzed using transmittance and reflectance spectra, which are measured using UV–vis-NIR double-beam spectrophotometer. Optical properties such as refractive index (n), extinction coefficient (k), optical conductivity (σ) and Urbach energy (E _u ) have been calculated as a function of Eu ^3+ concentration. Film thickness were evaluated using the refractive index dependence on wavelength. The films thickness were determined as 97.13, 122.62, 123.24, 117.14 and 128.25 nm, respectively, for Eu doped TiO _2 at 0,4, 6, 8 and 10 wt % doping concentration. The band gap values raised from 3.29 to 3.42 eV with increasing the Eu ^3+ dopant concentration. The highest electrical conductivity was found to be 3.01 × 10 ^−2 (Ω·cm) ^−1 at high doping level with 10 wt% Eu ^3+ . Scanning electron microscopy (SEM) analysis indicated consistent allocation of irregular and spherical shaped grains covering the substrate surface. The average grain size in range of 82.5—51.1 nm is observed and films show porous nature. The photocatalytic effect of TiO _2 : Eu ^3+ thin films is predicted from the degradation of methylene blue (MB) at room temperature under UV light irradiation. An enhancement in photocatalytic degradation observed by increasing the amount of Eu ^3+ due to increase in the (electron-hole) pair production and increase of film thickness. These results make TiO _2 : Eu ^3+ thin films as attractive candidate for photovoltaic cells and other optoelectronic device applications

Ellipsometric and ultrasonic studies of nano titanium dioxide specimens doped with Erbium

Nano Er-doped TiO _2 thin films prepared by sol-gel technique at different doping concentrations (5%, 7%, 9%, and 11%). The prepared thin films were studied through ultrasonic and ellipsometric measurements. Mechanical properties are known from the ultrasonic method that investigated the effect of the Er-doped amount on the cross-link density, bond strength, elastic properties, and stress-strain relation between atoms of TiO _2 thin films. Ellipsometric measurements studied the variation of optical transmittance, energy band gap, refractive index, Urbach energy roughness, and porosity with changing Er-doped amount. Finally, contact angle measurements are done to ensure the self-cleaning property of the prepared thin films. Results deduced that Er-doped enhanced greatly TiO _2 thin films, to be used in many industrial applications as self-cleaning glass fabrication

Smart synthesis of trimethyl ethoxysilane (TMS) functionalized core?shell magnetic nanosorbents Fe3O4@SiO2: Process optimization and application for extraction of pesticides

In the current study, a smart approach for synthesizing trimethyl ethoxysilane?decorated magnetic-core silica-nanoparticles (TMS-mcSNPs) and its effectiveness as nanosorbents have been exploited. While the magnetite core was synthesized using the modified M�ssbauer method, St�ber method was employed to coat the magnetic particles. The objective of this work is to maximize the magnetic properties and to minimize both particle size (PS) and particle size distribution (PSD). Using a full factorial design (2k-FFD), the influences of four factors on the coating process was assessed by optimizing the three responses (magnetic properties, PS, and PSD). These four factors were: (1) concentration of tetraethyl-orthosilicate (TEOS); (2) concentration of ammonia; (3) dose of magnetite (Fe3O4); and (4) addition mode. Magnetic properties were calculated as the attraction weight. Scanning electron microscopy (SEM) was used to determine PS, and standard deviation (�SD) was calculated to determine the PSD. Composite desirability function (D) was used to consolidate the multiple responses into a single performance characteristic. Pareto chart of standardized effects together with analysis of variance (ANOVA) at 95.0 confidence interval (CI) were used to determine statistically significant variable(s). Trimethyl ethoxysilane?functionalized mcSNPs were further applied as nanosorbents for magnetic solid phase extraction (TMS-MSPE) of organophosphorus and carbamate pesticides.Scopu

Influence of Mo+2 ion concentration on crystallization, microstructure, crystal imperfection and morphology of WO3 sprayed thin films

Compositional dependence of microstructure and morphological properties of Mo _x W _1−x O _3 (0.2 ≥ x ≥ 0.0 at. %) thin films was studied. MoWO _3 films were deposited by chemical spray pyrolysis technique on pre-heated glass substrates at 400 °C and the sedimentation rate was kept constant at 70 ml min ^−1 with the deposition time fixed at 10 min to keep the film thickness constant at about 650 ± 5 nm. The prepared thin films were studied using x-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and energy dispersive x-ray analysis (EDAX) techniques. The nature of the as-deposited films displayed by XRD showed beyond a reasonable doubt that they are amorphous. After thermal annealing at 500 °C for 2 h, all samples will be transferred to a polycrystalline having a triclinic structure. The microstructural parameters of the pure and doped samples were measured, using different methods and a comparison between them to determine the accuracy percentage of the measurement of these methods. The results also showed that the average crystallite size of the films decreased from 24 to 12 nm, on the contrary the internal microstrain increased from 23 × 10 ^−3 to 30 × 10 ^−3 with the addition of Mo element in WO _3 . Field emission scanning electron microscopy (FE-SEM) analysis also revealed that Mo dopant caused significant changes in the surface morphology of the films as well as an increase in particle size with increasing molybdenum concentration. The EDX results exhibited that the percentages of the isotropic elements Mo _x W _1−x O _3 agree well with those determined by atomic weight. In general, the results obtained in this study confirm that Mo _x W _1−x O _3 with these properties, is suitable for photovoltaic and optoelectronic applications