Optimization of a novel method based on solidification of floating organic droplet by high-performance liquid chromatography for evaluation of antifungal drugs in biological samples

In this study, a simple, rapid, and highly efficient liquid-phase microextraction method based on solidification of floating organic droplet was coupled with high performance liquid chromatography-photo diode array detection (HPLC-PDA) for determination of ketoconazole, clotrimazole, and miconazole as antifungal drugs. Central composite design (CCD) was used for optimization of several factors affecting the extraction efficiency. The optimized conditions were established to be 550 rpm for stirring rate, 35 min for extraction time, 57 °C for extraction temperature, 8.5 for solution pH, 10 μl for organic solvent volume, and 7% (w/v) of NaCl for ionic strength. Limit of detections (LODs) of the extraction method ranged from 0.01 to 0.1 μg L⁻¹ and the linear dynamic ranges (LDRs) ranged from 0.1 to 300 μg L⁻¹ for the three antifungal drugs. Relative standard deviations (RSDs) of the proposed method were 5-11%. Preconcentration factors in the range of 306-1350 were obtained at extraction time of 35 min. Finally, performance of the proposed method was evaluated for the extraction and determination of the drugs’ levels in microgram per liter in samples and satisfactory results were obtained.     

Quantification of the push-pull character of azo dyes and a basis for their evaluation as potential nonlinear optical materials

The push-pull characters of a large series of donor-acceptor substituted azo dyes—71 structures in all—have been quantified by the NN double bond lengths, d_NN, the ¹⁵N NMR chemical shift differences, Δδ_15N, of the two nitrogen atoms and the quotient, π^∗/π, of the occupations of the antibonding π^∗, and bonding π orbitals of this partial NN double bond. The excellent correlation of the occupation quotients with the bond lengths strongly infers that both π^∗/π and d_NN are excellent parameters for quantifying charge alternation in the push-pull chromophore and the molecular hyperpolarizability, β₀, of these compounds. By this approach, selected compounds can be appropriately considered as viable candidates for nonlinear optical (NLO) applications.     

Synthesis and photophysical properties of tetrafluorophenyl-modified carbazole oligomers

A series of tetrafluorophenyl-modified oligo(3,6-carbazole ethynylene)s (CfCzCf, CfCz2Cf, CfCz3Cf, (CfCz)2Cf, and Cf2CzCf2) were synthesized by a Pd/Cu-catalyzed Sonogashira coupling reaction and fully characterized. Their photophysical and electronic properties as well as their thermal stabilities were investigated. It is noteworthy that these tetrafluorophenyl modified compounds showed relative thermal stabilities and low-lying HOMO levels ranging from −5.54 to −5.60 eV, which might be the promising candidates for hole-transporting materials in OLEDs.     

Simultaneous Determination of Cadmium,Lead, Copper and Mercury Ions Using Organofunctionalized SBA‐15 Nanostructured Silica Modified Graphite–Polyurethane Composite Electrode

A new sensor has been developed for the simultaneous detection of cadmium, lead, copper and mercury, using differential pulse and square wave anodic stripping voltammetry (DPASV and SWASV) at a graphite–polyurethane composite electrode with SBA‐15 silica organofunctionalized with 2‐benzothiazolethiol as bulk modifier. The heavy metal ions were preconcentrated on the surface of the modified electrode at ?1.1 V vs. SCE where they complex with 2‐benzothiazolethiol and are reduced to the metals, and are then reoxidized. Optimum SWASV conditions lead to nanomolar detection limits and simultaneous determination of Cd²⁺, Pb²⁺, Cu²⁺ and Hg²⁺ in natural waters was achieved.     

Pressurised hot water extraction followed by simultaneous derivatization and headspace solid-phase microextraction and gas chromatography-tandem mass spectrometry for the determination of aliphatic primary amines in sewage sludge

In this paper we describe an environmentally friendly and sensitive method for the determination of ten primary amines in sewage sludge. The method is based on pressurised hot water extraction (PHWE) followed by simultaneous derivatization with pentafluorobenzaldehyde (PFBAY) and headspace solid-phase microextraction (HS-SPME) and subsequent gas-chromatography ion-trap tandem mass spectrometry (GC-IT-MS-MS) analysis. The influence of the main factors on the PHWE of sludge was optimized by a central composite design. For all species the optimal conditions were water at pH 4 as the extracting solvent, an extraction temperature of 100 °C and an extraction time of 15 min. The separation and detection of the ten amines by GC-IT-MS-MS took just 10 min and the entire process took approximately 1 h. Repeatability and reproducibility between days, expressed as RSD (%) (n = 5), were less than 19 and 24%, respectively. The average limit of detection (LOD) was of 65 μg kg⁻¹ s (range found 9-135) and the average limit of quantification (LOQ) was of 230 μg kg⁻¹ (range found 50-450) of dry weight (d.w.). Under optimized conditions we used this method to determine the compounds in industrial and municipal sewage sludge samples and in sludge from a potable water treatment plant. Methylamine and isobutylamine showed the highest levels in one of the industrial sewage sludge samples (404 and 543 mg kg⁻¹ (d.w.), respectively). To our knowledge, this paper presents for the first time the determination of ten primary amines in sewage sludge samples using PHWE.     

Effect of carbon nanotubes and their dispersion on thermal curing of polyimide precursors

The process of thermal imidization reaction is significant for temperature and time control in the polyimide industry. Here, we report the effect of carbon nanotubes and their states of dispersion on the thermal imidization of the precursor films of polyimide (poly(amic acid)) for the first time. The curing process was followed by measuring Fourier transform-infrared (FT-IR) spectra, fluorescence spectra, thermogravimetric-differential scanning calorimeter (TG-DSC) properties and the refractive indices of films. It was found that by evenly dispersing 1 wt% of carbon nanotubes assisted by a dispersant in the poly(amic acid),the full imidization temperature of the polyimide can be reduced from 300 °C to 250 °C. Different states of distribution of CNTs were observed by light microscopy and scanning electron microscopy, and proved that a better dispersion of carbon nanotubes dramatically enhanced the speed of imidization. Moreover, the DSC results showed that lower decomposition temperature of poly(amic acid) could be obtained with more uniform distribution of carbon nanotubes, which means the process of cyclodehydration of the poly(amic acid) was accelerated.     

Magnetic and thermodynamic properties of NdT2Ge2 (T=Pd, Ag) compounds

Physical properties of NdPd₂Ge₂ and NdAg₂Ge₂, crystallizing with the tetragonal ThCr₂Si₂-type crystal structure, were investigated by means of magnetic, calorimetric, electrical transport as well as by neutron diffraction measurements. The specific heat studies and neutron diffraction measurements were performed down to 0.30 K and 0.47 K, respectively. Both compounds exhibit antiferromagnetic ordering below T_N equal to 1.5 K for NdPd₂Ge₂ and 1.8 K for NdAg₂Ge₂. Neutron diffraction data for the latter germanide indicate antiferromagnetic collinear structure described by the propagation vector k=(0.5, 0, 0.5). The Nd magnetic moments equal to 2.24(5) μ_B at 0.47 K are aligned along the a-axis and have the +− sequence within the crystal unit cell. For NdPd₂Ge₂ only very small Bragg peaks of magnetic origin were observed in the neutron diffraction patterns measured below T_N, thus hampering determination of the magnetic structure. Both compounds exhibit metallic-like electrical conduction. From the specific heat data the crystal electric field (CEF) levels schemes were determined. Difference between the overall CEF splitting in the two compounds is correlated with their structural parameters.     

Synthesis, crystal structure and nonlinear optical property of Rb3V5O14

The new nonlinear optical crystal Rb₃V₅O₁₄ has been synthesized by solid state reaction and characterized by single-crystal X-ray diffraction, IR and thermogravimetric analysis. The crystal Rb₃V₅O₁₄ crystallizes in the trigonal system with space P31m (No. 157), a=b=8.7134(12) Å, c=5.2807(11) Å and α=90°, β=90°, γ=120°, Z=1, ρ=3.516 g/cm³. It is a layered structure that is very flat and strongly parallel to c. The V₅O₁₄ layer structure consists of corner-linked square and triangular pyramids. The layers are separated by Rb⁺ ions, which fit equally well on the V₅O₁₄ layer. The Kurtz powder SHG measurement, using 1064 nm radiation, showed that the second-harmonic generation efficiency of Rb₃V₅O₁₄ is about two times that of KDP.     

Solvothermal indium fluoride chemistry: Syntheses and crystal structures of K5In3F14, β-(NH4)3InF6 and [NH4]3[C6H21N4]2[In4F21]

The solvothermal syntheses and crystal structures of three indium fluorides are presented. K₅In₃F₁₄ (1) and β-(NH₄)₃InF₆ (2) are variants on known inorganic structure types chiolite and cryolite, respectively, with the latter exhibiting a complex and apparently novel structural distortion. [NH₄]₃[C₆H₂₁N₄]₂[In₄F₂₁] (3) represents a new hybrid composition displaying a unique trimeric metal fluoride building unit.     

Synthesis of boron suboxide (B6O) with ball milled boron oxide (B2O3) under lower pressure and temperature

Boron reacted with ball milled boron oxide under pressures between 1 and 5 GPa and at temperatures between 1300 and 1700 °C to afford boron suboxide (B₆O). Icosahedral B₆O grains with diameters ranging from 100 nm to 1.3 μm were prepared. The factors that affect the synthesis of B₆O are investigated. The best sample with crystal size up to 1.3 μm is obtained at 2 GPa and 1400 °C for 6 h. The indentation experiment gave an average Vickers hardness of 32.3 GPa for bulk B₆O sample, which is consistent with previous reports. Bulk B₆O sample exhibits oxidation resistance in air up to 1000 °C and mild oxidation in the temperatures of 1000-1200 °C, which is more oxidation resistant than diamond. It is possible that B₆O could be used as a substitute for diamond in industry because of its relatively mild synthesis conditions, high thermal stability and high hardness.