Dispersive solid-phase extraction based on MoS2/carbon dot composite combined with HPLC to determine brominated flame retardants in water

Analytical and Bioanalytical Chemistry - The method based on the dispersive solid-phase extraction (DSPE) by novel molybdenum disulfide modified with carbon dot (MoS2/CD) composite combined with...     

A liquid chromatography–tandem mass spectrometric assay for the antihypertensive agent azelnidipine in human plasma with application to clinical pharmacokinetics studies

A robust and sensitive high‐performance liquid chromatographic–tandem mass spectrometric (HPLC‐MS/MS) assay for the high‐throughput quantification of the antihypertensive drug azelnidipine in human plasma was developed and validated following bioanalytical validation guidelines. Azelnidipine and internal standard (IS), telmisartan, were extracted from human plasma by precipitation protein and separated on a C₁₈ column using acetonitrile–methanol–ammonium formate with 0.1% formic acid as mobile phase. Detection was performed on a turbo‐spray ionization source (ESI) and mass spectrometric positive multiple reaction monitoring mode (+MRM) using the respective transitions m/z 583.3 → 167.2 for azelnidipine and m/z 515.3 → 497.2 for IS. The method has a wide analytical measuring range from 0.0125 to 25 ng/mL. For the lowest limit of quantitation, low, medium and high quality controls, intra‐ and interassay precisions (relative standard deviation) were 3.30–7.01% and 1.78–8.09%, respectively. The drug was sufficiently stable under all relevant analytical conditions. The main metabolite of azelnidipine, M‐1 (aromatized form), was monitored semiquantitatively using the typical transition m/z 581.3 → 167.2. Finally, the method was successfully applied to a clinical pharmacokinetic study in human after a single oral administration of azelnidipine 8 mg. The assay meets criteria for the analysis of samples from large research trials. Copyright © 2014 John Wiley & Sons, Ltd.     

Direct and ultrasensitive optofluidic-based immunosensing assay of aflatoxin M1 in dairy products using organic solvent extraction

Aflatoxin M₁ (AFM₁), a highly toxic secondary metabolite, is present in a wide range of dairy products. In this study, we designed a simple, low-cost, reusable, and easy-to-operate immunosensing method for ultrasensitive detection of AFM₁ in dairy products by using a portable evanescent wave-based optofluidic biosensing platform (EOBP). The developed method provides the minimum detection limit of 5 ng/L, which is below the most restrictive standard imposed by the current regulations for AFM₁ in dairy products. The effect of several organic solvents, such as methanol, acetone, and acetonitrile, on the binding reaction of antibody-antigen in heterogeneous and homogeneous solutions was evaluated. Although the effect of organic solvents on the homogeneous binding reaction between antibody and antigen is more significant than that of heterogeneous binding reaction between antibody in solution and antigen immobilized onto the sensor surface, the fluorescence signal detected by EOBP is linearly dependent on AFM₁ concentration. Therefore, AFM₁ can be directly quantified even if the samples contain a certain organic solvent concentration. The robustness and stability of AFM₁-ovalbumin conjugate allow the regeneration of modified biosensor surface for more than 200 times, thereby achieving a cost-effective and reliable AFM₁ determination. The proposed method provides a rapid, ultrasensitive, and reliable AFM₁ determination in dairy products without complicated sample pretreatment process.     

Finite element analysis of the temperature field in laser cladding of Ni-based powders on teeth surfaces of the helical gear

The temperature field formed in the process of laser cladding of worn teeth surfaces of the gear shaft is simulated by the finite element analysis software. Isothermal lines inside the tooth are obtained. Simulated results are compared with experimental data. Recommendations are given on improvement of the cladding technology to provide a durable continuous coating.     

Copolymers of methyl methacrylate with N‐trifluorophenyl maleimides: High glass transition temperature and low birefringence polymers

Copolymers of methyl methacrylate (MMA) with 2,3,4‐ and 2,4,6‐trifluorophenyl maleimides (TFPMIs) were synthesized by a free radical initiator, azobisisobutyronitrile, in 1,4‐dioxane and also in bulk. The refractive indexes of the copolymers were in the range of 1.49–1.52 at 532 nm. The T_gs were 133–195 °C depending on copolymer compositions. In addition, the copolymers were thermally stable, T_d > 350 °C. The orientational and photoelastic birefringence of the copolymers were also investigated. As both of the orientational and photoelastic birefringences of PMMA are negative, whereas those of poly(TFPMI)s are positive, we could obtain nearly zero orientational and photoelastic birefringence polymers when the ratios of 2,3,4‐TFPMI/MMA were 15/85 and 5/95 mol %, respectively. For 2,4,6‐TFPMI, zero orientational and photoelastic birefringences could be obtained when the ratios of 2,4,6‐TFPMI/MMA were 12/88 and 3/97 mol %, respectively. The T_gs of those copolymers with zero birefringences were in the range of 135–140 °C. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Design,synthesis, and self‐assembly manipulating of polymerized ionic liquids contained imidazolium based on “Jacketing” effect

A series of novel polymerized ionic liquids (PILs) contained imidazolium, poly (2,5‐bis{[6‐(1‐butyl‐3′‐imidazolium)hexyl] oxy carbonyl}styrene salts) (denoted as P1? X^?, X^??Br^?, BF₄^?, PF₆^? and TFSI^?) were successfully synthesized via radical polymerization. The chemical structures of the monomers and their corresponding PILs were confirmed by ¹H NMR, ¹³C NMR, and Fourier transform infrared spectroscopy. Thermogravimetric analysis results showed that these PILs had excellent thermal stability. The phase transitions and liquid‐crystalline (LC) behaviors of these polymers were investigated by differential scanning calorimetry, polarized light microscopy (PLM), and wide‐angle X‐ray diffraction. The combined experimental results showed that all the PILs could form hexagonal columnar (?H) LC ordered structures because of the strong interaction between the anions and cations in the side groups except for P1? TFSI^?. The conductivities of monomers and PILs were sketchily investigated, and monomers had higher conductivities than those of conprespoding PILs. For comparison, we have synthesized a polymer without counter‐anion, but similar to the chemical structure of P1? X^?, poly (2, 5‐bis{[6‐(4‐butoxy‐4′‐oxy phenyl) hexyl] oxycarbonyl} styrene) (denoted as P2). In this case, phenyl took place of imidazolium of side chain, and LC ordered structure did not form. The comparison between P1? X^? and P2 suggested that ion played an important role in the constructing of LC ordered structure. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

gem‐Dimethyl‐bearing C‐Glucosides as Sodium‐glucose Co‐transporter 2 (SGLT2) Inhibitors

Three novel gem‐dimethyl C‐glucosides were designed as sodium‐glucose co‐transporter 2 (SGLT2) inhibitors, and their syntheses started from D‐glucose and three 2‐substituted‐5‐bromobenzoic acids were achieved via a facile 8‐step protocol, with the key step being anhydrous aluminum chloride‐catalyzed Friedel‐Crafts alkylation of tertiary alcohols and phenetol. These three SGLT2 inhibitors were evaluated in vivo with a mice oral glucose tolerance test (OGTT), and the anti‐hyperglycemic activities of all these three compounds were comparable with that of the positive control Dapagliflozin.