Chemical durability of MoO<Subscript>3</Subscript>-P<Subscript>2</Subscript>O<Subscript>5</Subscript> and K<Subscript>2</Subscript>O-MoO<Subscript>3</Subscript>-P<Subscript>2</Subscript>O<Subscript>5</Subscript> glasses

Thermal and chemical durability studies of the phosphate glasses belonging to the binary MoO₃-P₂O₅ and the ternary K₂O-MoO₃-P₂O₅ systems are reported. The chemical resistant attack tests carried out on the free alkaline MoO₃-P₂O₅ glasses show that the glass associated with the P/Mo ratio 2 has the high chemical durability. It shows also a high glass transition temperature value. The above findings are interpreted in terms of the cross-link density of the glasses and the strength of the M-O bonds (M=P, Mo). The influence of K₂O addition on the properties (density, T _g, durability) of this binary high water resistant glass is studied. It is found that the chemical durability along with the other physical properties are reduced by the incroporation of K₂O in the glass matrix. The results were explained by assuming the formation of non-bridging oxygens and weak bonds. The mechanism of the dissolution of these glasses is proposed.     

LC Determination of Adulterated Saffron Prepared by Adding Styles Colored with Some Natural Colorants

A high-performance liquid chromatographic method previously developed (Lozano et al. in J Chromatogr A 830:477–483, 1999) for simultaneous detection, identification and quantification of the secondary metabolites in commercial saffron was extended for the detection of adulterated saffron prepared by adding styles colored with the natural colorants extracted from saffron petals, safflower, madder and red beet. The chromatograms of the methanol-water (50%, v/v) extracts of pure and adulterated saffron were obtained at the assayed wavelengths, 402 (or 254), 260 and 535 (or 440) nm and then by applying two-way analysis of variance (ANOVA) to the obtained data the presence of the styles colored with the colorant of safflower (>14.3%), styles colored with the colorant of madder (>9.1%) and styles colored with the colorant of red beet (>14.3%) in saffron were significantly detected. But the detection of adulterated saffron prepared with the colorant of saffron petals was not successful.     

A novel, selective, and rapid fluorimetric method for the simultaneous analysis of coproporphyrin and uroporphyrin in urine

A simple and rapid spectrofluorimetric method is described for the determination of the closely overlapping mixture of coproporphyrin (CP) and uroporphyrin (UP) in urine samples. Matrix Isopotential Synchronous Fluorescence Spectrometry (MISFS) was applied to improve the spectral resolution for the severely overlapped spectra of the urinary porphyrins. First-order derivative technique eliminates the background interference of each component on the other. Using these two techniques together, selectivity was improved, while maintaining a high sensitivity, and time-consuming separation processes and multiple scanning processes were avoided. The limits of detection were 0.15 nmol L⁻¹ and 0.1 nmol L⁻¹ for CP and UP, respectively. The concentrations of CP and UP were determined from the peak amplitudes of the Derivative Matrix Isopotential Synchronous Fluorescence (DMISF) spectra, at their detection points where the interference was suppressed. Porphyrins excretion in urine samples, collected from normal subjects, was studied. A comparison between the new method and the anion-exchange chromatographic method of Martinez and Mills was established using Bland-Altman method and the results indicate that these two methods are in a good agreement with each other.     

Spectrophotometric catalytic determination of ultra-trace amounts of selenium based on the reduction of resazurin by sulphide

A sensitive catalytic method for determining ng ml^? concentration of selenium is described. The method is based on the catalytic action of Se(IV) on the reduction of resazurin by sulphide, monitored spectrophotometrically at 605 nm. The linearity range of the calibration graph is dependent on the concentration of sulphide. The variables affecting the rate of the reaction were investigated and the optimum conditions were established. The method is simple, rapid, precise, sensitive and widely applicable. As low as 8.0 × 10^?4 μg ml^?1 of selenium can be determined. The relative standard deviation of seven determination of 10 ng Se was 0.7%. The determination of Se(IV) in the presence of Se(VI) and the determination of total selenium are also described.     

Modeling of microreactor for syngas production by catalytic partial oxidation of methane

Fixed-bed reactors for the catalytic partial oxidation of methane (CPOM) to produce synthesis gas still pose hot spots problems. Microreactor is a good alternative reactor proposed to resolve these problems. In this paper, synthesis gas (hydrogen and carbon monoxide) production was investigated by a two-dimensional numerical model of single microchannel. CFD modeling with detailed chemistry was conducted to understand the CPOM on platinum (Pt) catalyst. Gas inlet velocity, microchannel pressure, and fuel to air ratio (F/A) are selected as the effective parameters on microchannel performance. Study results show that Reynolds number has considerable effect on methane conversion, hydrogen to carbon monoxide ratio (H2/CO), and product distribution. Increasing gas inlet velocity causes all the above parameters to decrease. It is noted that increasing microchannel pressure and decreasing the ratio of fuel to air cause the decrease of the H2/CO ratio.     

CuBr/Et3N‐Promoted Reactions of 2‐Aminobenzamides and Isothiocyanates: Efficient Synthesis of Novel Quinazolin‐4(3H)‐ones

A series of novel quinazolin‐4(3H)‐one derivatives were efficiently synthesized starting from isatoic anhydride. First, reaction of isatoic anhydride and amines in H₂O at room temperature afforded 2‐aminobenzamides. Then, CuBr/Et₃N promoted reaction of 2‐aminobenzamides and different aryl isothiocyanates in DMF at 80° afforded the title compounds in good yield.     

Successive ratio-derivative spectra as a new spectrophotometric method for the analysis of ternary mixtures

A new spectrophotometric method was developed for the simultaneous determination of ternary mixtures, without prior separation steps. This method is called the successive derivative ratio spectra. The method is based on the successive derivative of ratio spectra in two steps. The mathematical explanation of the procedure is illustrated. In order to evaluate the applicability of the method a model data as well as an experimental data were tested. The results from experimental data relating to the simultaneous spectrophotometric determination of Zn(II), Co(II) and Ni(II) based on their complexes with 1-(2-pyridylazo)2-naphthol in micellar media were presented as real model for resolution of the ternary systems. The method was compared with partial least squares (PLS) method.     

Simulations of the PDF functions for dilute colloidal suspensions of molecular particles flowing in mesopores with rough surface boundaries

Simulations have been carried out to analyze the dynamics of dilute colloidal suspensions of macromolecular particles in solutions flowing in pores, subject to hydrodynamic forces, Brownian motion and stochastic collisions at rough pore boundaries in a two-dimensional spatial frame. A theoretical model is developed and intensively analyzed for the treatment of the mechanical restitution of the particles due to dynamic collisions at these boundaries. In particular we are able to calculate the Probability distribution functions for the spatial positions and the orientations of rod-like particles inside the pores. The results are presented for different widths of pore channels referenced to the size of a rod-like particle. These simulations are general in the sense that they are developed for confining and open pore channels, rough at the nano scale. The simulations also permit calculating the nematic order parameters for colloidal suspensions; the model calculation is applied for dilute colloidal suspensions of carbon nano-tubes in an aqueous single-stranded DNA solution flowing inside pores. Our calculated nematic order results for dilute suspensions of particles of known lengths flowing inside porous systems should indicate, when coupled to birefringence and dichroism experimental results, the possibility to estimate the pore widths for these systems.     

Synthesis and cytotoxicity of novel chromenone derivatives bearing 4-nitrophenoxy phenyl acryloyl moiety

This work describes synthesis of novel chromenone derivatives bearing 4-nitrophenoxy phenyl acryloyl moiety through the reaction of 4-(4-nitrophenoxy)benzaldehydes and 3-acetyl-2H-chromen-2-ones in refluxing toluene. Cytotoxicity of all compounds was evaluated using a tetrazolium (MTT) colorimetric assay against human breast cancer cell line, MDA-MB-231.     

Synthesis of 2‐aryl‐1‐arylmethyl‐1H‐1,3‐benzimidazoles catalysed by ferric ammonium sulfate (NH4Fe(SO4)2) under solvent‐free conditions

NH₄Fe(SO₄)₂ was found to be a mild and effective catalyst for the selective synthesis of 2‐aryl‐1‐arylmethyl‐1H‐1,3‐benzimidazoles under solvent‐free conditions. Copyright © 2015 John Wiley & Sons, Ltd.