Simultaneous determination of 11 related impurities in propofol by gas chromatography/tandem mass spectrometry coupled with pulsed splitless injection technique

A variety of related impurities, including starting materials, process impurities, and degradation products, can be detected in propofol. In this article, a sensitive and selective GC‐MS/MS method using pulsed splitless injection technique for the determination of 11 main related impurities in propofol in one chromatogram is investigated. This method is extensively validated for its linearity, recovery, precision, LOD, and LOQ, and is able to detect trace‐level related impurities (LOD = 0.2–5.6 μg/g) in propofol bulk drug. Stressed tests proposed that oxidative degradation, photolytic degradation, and heat are the main causes for the formation of degradation products in propofol.     

Rapid determination of α‐tocopherol in cereal grains using dispersive liquid–liquid microextraction followed by HPLC

The traditional for the determination of α‐tocopherol in cereal grains includes saponification of a sample followed by liquid–liquid extraction, and it is time‐ and solvent consuming. In this study, a dispersive liquid–liquid microextraction (DLLME) method was developed to extract α‐tocopherol in situ from the saponified grain sample solution. The DLLME experimental parameters including the type and volume of extractants, the volume of dispersers, the addition of salt and the extraction/centrifuging time were examined and optimized. The recommended analytical procedure showed excellent precision (relative SDs of the α‐tocopherol amount of 3.1% over intraday and 7.2% over interday), high sensitivity (the detection limit of 1.9 ng/mL), and strong recovery values (88.9–102.5%). In addition, statistical analyses showed no significant difference between the detected amounts of α‐tocopherol found by the standardized method and this new procedure. The method was successfully applied to determining the amounts and distribution of α‐tocopherol in 14 cereal grain samples.     

Comparison of different sample pre‐treatments for multi‐residue analysis of organochlorine and pyrethroid pesticides in chrysanthemum by gas chromatography with electron capture detection

The widespread use of insecticides in Chinese herbal medicines has created a compelling need for the development of a multiresidue analytical method to help assure herbs safety. The operating variables affecting the performance of the multiresidue analysis of 34 organochlorine and 12 pyrethroid pesticides in chrysanthemum, a widely used kind of Chinese herbal medicines, were evaluated. Three different extraction solvents including n‐hexane and its mixtures with acetone and petroleum ether were compared, and n‐hexane was found to be an appropriate option. A combination of gel permeation chromatography and SPE was selected as the optimum cleanup, in comparison with dispersive SPE, or the two former methods alone. The determination of the 46 pesticide residues in the spiked chrysanthemum samples was performed by GC with electron capture detection. The average recoveries ranged from 71.3 to 102.6% with RSDs of 1.4–15.7% for all of the pesticides. The LOQs were in the range of 0.0015–0.2 mg/kg, while the LODs were between 0.0005 and 0.1 mg/kg. The satisfactory accuracy, and precision, in combination with a good separation and few interferences, have demonstrated the strong potential of this technique for its application in chrysanthemum analysis.     

Coagulation behaviors and in-situ flocs characteristics of composite coagulants in cyanide-containing wastewater: Role of cationic polyelectrolyte

In this paper,composite coagulants(PFS,PFSC05,PFSC1 and PFSC5),prepared by mixing polyferric sulfate(PFS)and cationic polyelectrolyte(CP)coagulants with different weight percent(Wp)of CP(Wp=0%,0.5%,1%and 5%,respectively),were adopted to treat cyanide-containing wastewater.PFSC5 exhibited superior coagulation performances at optimal conditions:the removal of total cyanide(TCN)and chemical oxygen demand(COD)was 95%–97%and 50%–55%,respectively.The effects of CP on the properties and structure of flocs were investigated by laser diffraction instrument and small-angle laser light scattering(SALLS),respectively.The results show that the flocs of PFSC5 have higher growth rate,higher strength factor and lower recovery factor than other flocs.They are also much denser and more uniform owing to the higher fractal dimension(Df)and less microflocs(10–100 m).Furthermore,the dense structure of the PFSC5 flocs can be restored after shear and is more resistant to hydraulic conditions.Particularly,detailed morphology evolution of the flocs was in-situ detected by on-line particle imaging.Due to strong ionic strength in wastewater,the CP in PFSC5 plays a significant role of adsorption,while the main mechanism of CP is electrostatic patch aggregation during the PFSC05 systems.     

Novel Route to Functionalized Indans via Formal [3 + 2] Cycloadditions of 1-Benzylbenzotriazoles with Alkenes

α-Functionalized 1-benzylbenzotriazoles (3, 4 and 12), derived from the lithiation of 1-(2,3-dimethoxybenzyl)benzotriazole 2 followed by reactions with electrophiles, or from the condensation of benzyl alcohol 11 with benzotriazole, undergo formal [3 + 2] cycloadditions with styrenes upon treatment with ZnBr₂ to give functionalized indans (9, 10, 13 and 14).     

Atom-Economic Route to Densely Functionalized Thiophenes via Base-Catalyzed Rearrangement of 5-Propargyl-2H-thiopyran-4(3H)-ones

An atom-economic route to densely functionalized thiophenes has been developed via base-catalyzed rearrangement of 5-propargyl-2H-thiopyran-4(3H)-ones involving tandem retro-thio Michael addition, propargyl isomerization, and intramolecular thio-addition to allenes.     

Direct Blue 71 staining as a destaining‐free alternative loading control method for Western blotting

In Western blotting, a suitable loading control is indispensable for correcting errors in the total amount of loaded protein. Immunodetection of housekeeping proteins and total protein staining have traditionally been used as loading control methods. Direct Blue 71 (DB71) staining—a novel, sensitive, dye‐binding staining method compatible with immunodetection—may offer advantages over these traditional loading control methods. Three common neuroscientific samples (human plasma, human oligodendrocytes, and rat brain) were employed to assess DB71 staining as a loading control method for Western blotting. DB71, CBB, one traditional housekeeping protein, and one protein of interest were comparatively assessed for reliability and repeatability and linear dynamic range over 2.5–40 μg of protein loaded. DB71's effect on the reliability and repeatability and linear dynamic range of immunoreaction were also assessed. Across all three sample types, DB71 was either equivalent or superior to CBB and housekeeping protein‐based methods in terms of reliability and repeatability and linear dynamic range. Across all three sample types, DB71 staining did not impair the reliability and repeatability or linear dynamic range of immunoreaction. Our results demonstrate that the DB71 staining can be used as a destaining‐free alternative loading control method for Western blotting.     

Thermodynamics of AOT Micelle Formation in Ethylammonium Nitrate

AOT micelle formation in ethylammonium nitrate (an ionic liquid) was investigated by surface tension measurement in this article and the critical micelle concentrations (cmc) of AOT in ethylammonium nitrate at different temperatures were obtained. The thermodynamic parameters of micelle formation were obtained according to the two-phase thermodynamic model. The results suggested that the micelle formation of AOT in ethylammonium nitrate was a spontaneous, endothermal and entropy-increasing process.     

In situ self-assembly synthesis of gold nanoparticle arrays on polystyrene microspheres and their surface plasmon resonance

Gold (Au) nanoparticle arrays with tunable morphology and optical characteristics were synthesized by in-situ self-assembly process that occurred on the surface of aniline-modified polystyrene (PS) microspheres. The method can be used to control the growth of both single and aggregated Au nanoparticle arrays on PS microsphere surface. This method could also be adapted for synthesis of other noble metals hybrid materials, which opens exciting opportunities for their practical applications.