Synthesis and application of molecularly imprinted nanoparticles combined ultrasonic assisted for highly selective solid phase extraction trace amount of celecoxib from human plasma samples using design expert (DXB) software

In this work molecular imprinted nanoparticles (MINPs) was synthesized and applied for ultrasonic assisted solid phase extraction of celecoxib (CEL) from human plasma sample following its combination by HPLC–UV. The MINPs were prepared in a non-covalent approach using methacrylic acid as monomer, CEL as template, ethylene glycol dimethacrylate as cross-linker, and 2,2-azobisisobutyronitrile (AIBN) as the initiator of polymerization. pH, volume of rinsing and eluent solvent and amount of sorbent influence on response were investigated using factorial experimental design, while optimum point was achieved and set as 250 mg sorbent, pH 7.0, 1.5 mL washing solvent and 2 mL eluent by analysis of results according to design expert (DX) software. At above specified conditions, CEL in human plasma with complicated matrices with acceptable high recoveries (96%) and RSD% lower than 10% was quantified and estimated.The proposed MISPE-HPLC–UV method has linear responses among peak area and concentrations of CEL in the range of 0.2–2000 μg L⁻¹, with regression coefficient of 0.98. The limit of detection (LOD) and quantification (LOQ) based on three and ten times of the noise of HPLC peaks correspond to blank solution were 0.08 and 0.18 μg L⁻¹, respectively.     

Electron diffraction studies of variable periodicity in decagonal quasicrystals in aluminium-cobalt alloys

The reciprocal space vectors of the decagonal phase can be generated by a slight distortion of the basis vectors of a regular icosahedron to induce commensuration in one dimension. In different alloys a multiple of this basic periodicity has been observed. In particular, in Al-Co alloys, apart from the basic periodicity, doubling, tripling and quadrupling of this basic underlying periodicity has been observed. Stereographic analysis, simulation and experimental observation of electron diffraction patterns have been used to explore the nature of this varying periodicity in detail.     

Application of Graphene as a Sorbent for Simultaneous Preconcentration and Determination of Trace Amounts of Cobalt and Nickel in Environmental Water and Vegetable Samples

A new method using a column packed with graphene as adsorbent was developed for the preconcentration of trace amounts of cobalt (Co) and nickel (Ni) prior to their determinations by flame atomic absorption spectrometry. Several factors influencing the extraction efficiency of Co and Ni and their subsequent determinations, such as pH, amounts of the chelating agent, flow rates of sample and eluent solution, eluent type and its volume, breakthrough volume, and adsorption capacity were established. Under the optimum conditions, the calibration graphs were linear in the range of 4.0‐200.0 μg L^?1 and 5.0‐200.0 μg L^?1 with detection limits of 0.36 μg L^?1 and 0.51 μg L^?1 for Co and Ni, respectively. Good relative standard deviations for ten determinations of 100.0 μg L^?1 of Co and Ni were 3.2 and 3.6%, respectively. The results for determination of Co and Ni in tap water, river water, sea water, vegetable and spiked samples have demonstrated the accuracy and applicability of the proposed method. To validate the proposed method, three certified reference materials of environment water (GSBZ 50030‐94 and GSB 07‐1186‐2000) and tomato leaf (GSBZ 51001‐94) were analyzed, and the determined values were in good agreement with the certified values.     

TiO2 photocatalysis for the degradation of pollutants in gas phase: From morphological design to plasmonic enhancement

TiO₂-based photocatalysis has become a viable technology in various application fields such as (waste)water purification, photovoltaics/artificial photosynthesis, environmentally friendly organic synthesis and remediation of air pollution. Because of the increasing impact of bad air quality worldwide, this review focuses on the use and optimization of TiO₂-based photocatalysts for gas phase applications. Over the past years various specific aspects of TiO₂ photocatalysis have been reviewed individually. The intent of this review is to offer a broad tutorial on (recent) trends in TiO₂ photocatalyst modification for the intensification of photocatalytic air treatment. After briefly introducing the fundamentals of photocatalysis, TiO₂ photocatalyst modification is discussed both on a morphological and an electronic level from the perspective of gas phase applications. The main focus is laid on recent developments, but also possible opportunities to the field. This review is intended as a solid introduction for researchers new to the field, as well as a summarizing update for established investigators.     

Determination of the Onset of Asphaltene Precipitation by Visible Ultraviolet Spectrometry and Spectrofluorimetry

Abstract

Asphaltene deposition is a problem for the petroleum industry, affecting the production, transport, and storage of crude oil. The aim of this work is to develop and compare different methods to determine asphaltene precipitation. Two asphaltene fractions, one extracted from a Brazilian crude oil sample and the other from petroleum distillation residue, were evaluated by using model systems constituted of toluene/n-heptane in different compositions, using visible ultraviolet spectrometry and spectrofluorimetry. The results of the precipitation tests carried out by these two methods agreed, indicating they are effective to analyze asphaltene deposition and the performance of chemicals as asphaltene stabilizers.     

Cost‐efficient magnetic nanoporous carbon derived from citrus peel for the selective adsorption of seven insecticides

A magnetic solid‐phase extraction adsorbent that consisted of citrus peel‐derived nanoporous carbon and silica‐coated Fe₃O₄ microspheres (C/SiO₂@Fe₃O₄) was successfully fabricated by co‐precipitation. As a modifier for magnetic microspheres, citrus peel‐derived nanoporous carbon was not only economical and renewable for its raw material, but exerted enormous nanosized pore structure, which could directly influence the type of adsorbed analytes. The C/SiO₂@Fe₃O₄ also possessed the advantages of Fe₃O₄ microspheres like superparamagnetism, which could be easily separated magnetically after adsorption. Integrating the superior of biomass‐derived nanoporous carbon and Fe₃O₄ microspheres, the as‐prepared C/SiO₂@Fe₃O₄ showed high extraction efficiency for target analytes. The obtained material was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X‐ray photoelectron spectroscopy, and the Brunauer–Emmett–Teller method, which demonstrated that C/SiO₂@Fe₃O₄ was successfully synthesized. Under the optimal conditions, the adsorbent was selected for the selective adsorption of seven insecticides before gas chromatography with mass spectrometry detection, and good linearity was obtained in the concentration range of 2–200 μg/kg with the correlation coefficient ranging from 0.9952 to 0.9997. The limits of detection were in the range of 0.03–0.39 μg/kg. The proposed method has been successfully applied to the enrichment and detection of seven insecticides in real vegetable samples.     

A contact process with a semi-infected state on the complete graph

In this paper, we are concerned with a contact process with a semi-infected state on the complete graph C_n with n vertices. Our model is a special case of a general model introduced by Schinazi in 2003. In our model, each vertex is in one of three states, namely, “healthy,” “semi-infected,” or “fully-infected.” Only fully-infected vertices can infect others. A healthy vertex becomes semi-infected when being infected while a semi-infected vertex becomes fully-infected when being further infected. Each (semi- and fully-) infected vertex becomes healthy at constant rate. Our main result shows a phase transition for the waiting time until extinction of the fully-infected vertices. Conditioned on all the vertices are fully-infected when t = 0, we show that fully-infected vertices survive for exp?{O(n)} units of time when the infection rate λ > 4 while they die out in O(log?n) units of time when λ < 4.     

An improved watermarking method based on double random phase encoding technique

An improved watermarking method, based on the double random phase encoding technique and the cascaded-phases iterative algorithm and random-phase-shift algorithm, is proposed. This method can significantly reduce the needs of watermarking information storage for different multimedia products, and provide a reasonable criterion of determining the authenticity of a product for the copyright owner. This method can also be applied to track the source of copies. The effectiveness of this method was verified through numerical simulations.