Modified ionic liquid cold-induced aggregation dispersive liquid-liquid microextraction followed by atomic absorption spectrometry for trace determination of zinc in water and food samples

We report on a new method for the microextraction and determination of zinc (II). The ion is accumulated via ionic-liquid cold-induced aggregation dispersive liquid-liquid microextraction (IL-CIA-DLLME) followed by flame atomic absorption spectrometry (FAAS). The ionic liquid (IL) 1-hexyl-3-methylimidazolium hexafluorophosphate is dispersed into a heated sample solution containing sodium hexafluorophosphate as a common ion source. The solution is then placed in an ice-water bath upon which a cloudy solution forms due to the decrease of the solubility of the IL. Zinc is complexed with 8-hydroxyquinoline and extracted into the IL. The enriched phase is dissolved in a diluting agent and introduced to the FAAS. The method is not influenced by variations in the ionic strength of the sample solution. Factors affecting the performance were evaluated and optimized. At optimum conditions, the limit of detection is 0.18???g?L^?1, and the relative standard deviation is 3.0% (at n?=?5). The method was validated by recovery experiments and by analyzing a certified reference material and successfully applied to the determination of Zn (II) in water and food samples.

SbCl5.SiO2: an efficient alternative for one-pot synthesis of 1,2,4,5-tetrasubstituted imidazoles in solvent or under solvent-free condition

In a one-pot four-component reaction, an aldehyde, an amine, benzil and ammonium acetate were condensed for the synthesis of 1,2,4,5-tetrasubstituted imidazoles in the presence of silica supported antimony pentachloride (SbCl₅.SiO₂) in improved yields. The catalyst is recoverable by simple filtration and can be used in the subsequent reactions.     

Modified nanoporous silicas for oral delivery of the water insoluble organotin compound: loading and release of methylphenyltin dichloride as an anti-tumor drug model

Different nanoporous silica materials, MCM-41, MCM-48 and SBA-15, were modified by pyridine and their applications for oral drug delivery system were evaluated. These pyridine functionalized nanoporous silicas were loaded with a water insoluble diorganotin(IV) dichloride complex as an antitumor drug model and its release from them were investigated by changing pH. An efficient pH-responsive carrier system was constructed by coordination of the pyridine group in modified nonoporous materials to tin complex. In vitro, releasing of loaded tin complex was studied in three different kinds of fluids, including a simulated gastric medium and a simulated body fluid. The loading and releasing of the diorganotin(IV) dichloride from various modified nanoporous silicas and also a non-porous silica (SiO₂) were investigated, and the results were compared. In addition, the effect of some factors such as pH, time of loading and releasing were investigated through this study.     

Synthesis and characterization of silica-supported Pd nanoparticles and its application in the Heck reaction

Well-dispersed palladium nanoparticles immobilized onto modified silica(SiO 2-pr-NH-cyanuric-SH) have been prepared in some facile steps.The catalyst exhibits high catalytic activity in the Heck reaction,and can be easily recovered and reused without significant loss of its activity in several runs.     

A novel technique for simultaneous diagnosis and radioprotection by radioactive cerium oxide nanoparticles: study of cyclotron production of <Superscript>137m</Superscript>Ce

Application of nanoparticles in nuclear medicine has aimed to develop diagnosis and therapeutic techniques. Cerium oxide nanoparticles (CNPs) are expected to be useful for protection of healthy tissue from radiation-induced harm and could serve therapeutic function. Among a variety of cerium radioisotopes, ^137mCe (T _1/2 = 34.4 h, IT (99.22%), β⁺ (0.779%)) could be a novel candidate radionuclide in the field of diagnosis owing to its appropriate half-life, 99.91% natural abundance of target and its intense gamma line at 254.29 keV. In this study, ^137mCe excitation function via the ^natLa(p,3n) reaction was calculated by TALYS-1.2 and EMPIRE-3 codes. The excitation function calculations demonstrated that the ^natLa(p,3n)^137mCe reaction leads to the formation of the ^136/138Ce isotopic contamination in the 22–35 MeV energy range. Interestingly, the isotopic impurities of ^137mCe could serve radio protector function. Overall results indicate that the cyclotron produced ^137mCeO₂ nanoparticles by irradiation of a target encompassing lanthanum oxide nanoparticles could be a potent alternative for conventional diagnostic radionuclides with simultaneous radioprotection capacity.     

Accurate dispensing of volatile reagents on demand for chemical reactions in EWOD chips

Digital microfluidic chips provide a new platform for manipulating chemicals for multi-step chemical synthesis or assays at the microscale. The organic solvents and reagents needed for these applications are often volatile, sensitive to contamination, and wetting, i.e. have contact angles of <90° even on the highly hydrophobic surfaces (e.g., Teflon? or Cytop?) typically used on digital microfluidic chips. Furthermore, often the applications dictate that the processes are performed in a gas environment, not allowing the use of a filler liquid (e.g., oil). These properties pose challenges for delivering controlled volumes of liquid to the chip. An automated, simple, accurate and reliable method of delivering reagents from sealed, off-chip reservoirs is presented here. This platform overcomes the issues of evaporative losses of volatile solvents, cross-contamination, and flooding of the chip by combining a syringe pump, a simple on-chip liquid detector and a robust interface design. The impedance-based liquid detection requires only minimal added hardware to provide a feedback signal to ensure accurate volumes of volatile solvents are introduced to the chip, independent of time delays between dispensing operations. On-demand dispensing of multiple droplets of acetonitrile, a frequently used but difficult to handle solvent due to its wetting properties and volatility, was demonstrated and used to synthesize the positron emission tomography (PET) probe [(18)F]FDG reliably.     

Interactions between β-carboline alkaloids and bovine serum albumin: Investigation by spectroscopic approach

β-Carboline alkaloids are present in medicinal plants such as Peganum harmala L. that have been used as folk medicine in anticancer therapy. BSA¹ is the major soluble protein constituent of the circulatory system, and has many physiological functions including the transport of a variety of compounds. This study is the first attempt to investigate the binding of β-carboline alkaloids to BSA by using a constant protein concentration and varying drug concentrations at pH 7.2. FTIR² and UV–Vis³ spectroscopic methods were used to analyze the binding modes of β-carboline alkaloids, the binding constants and the effects of drug complexation on BSA stability and conformation. Spectroscopic evidence showed that β-carboline alkaloids bind BSA via hydrophobic interaction and van der Waals contacts along with H-bonding with the –NH groups, with overall binding constants of K_{harmine–BSA}=2.04×10⁴ M^?1, K_{tryptoline–BSA}=1.2×10⁴ M^?1, K_{harmaline–BSA}=5.04×10³ M^?1, K_{harmane–BSA}=1.41×10³ M^?1 and K_{harmalol–BSA}=1.01×10³ M^?1, assuming that there is one drug molecule per protein. The BSA secondary structure was altered with a major decrease of α-helix from 64% (free protein) to 59% (BSA–harmane), 56% (BSA–harmaline and BSA–harmine), 55% (BSA–tryptoline), 54% (BSA–harmalol) and β-sheet from 15% (free protein) to 6–8% upon β-carboline alkaloids complexation, inducing a partial protein destabilization.     

Thermodynamical Properties of Quark-Gluon Plasma and Effects of Bulk Viscosity

In this paper, we use equation of state, temperature and bulk viscosity of the quark gluon plasma and calculate some cosmological and thermodynamical quantities. In order to obtain such quantities we choose special case of energy density in terms of Hubble parameter. We apply the approximation solution and obtain the exact form of scale factor, temperature and bulk viscous stress. Finally, we draw some figures for the geometric and thermodynamic quantities in terms of time.     

Thermoluminescence kinetics analysis of α-Al2O3:C at different dose levels and populations of trapping states and a model for its dose response

Kinetic analysis of a α-Al₂O₃ (TLD-500) thermoluminescent (TL) dosimeter was performed following irradiating the samples with ⁶⁰Co gamma rays. The number of glow peaks contained in the complex glow curve of this phosphor was identified using the T_m ? T_stop method, which demonstrates three component glow peaks. A computerized glow curve deconvolution (CGCD) program was used to determine the trapping parameters of the three constituent glow peaks obtained at different dose levels and different populations of trapping states. To analyze the number of constituent glow peaks, we used a kinetic model to describe both the irradiation and heating stages. The predictions of the model for the TL response agreed well with the experimental data when three dosimetry traps were incorporated.