Determination of ochratoxin A in grains by immuno-ultrafiltration and HPLC-fluorescence detection after postcolumn derivatisation in an electrochemical cell

The paper presents a new sample clean-up method based on immuno-ultrafiltration for the analysis of ochratoxin A in cereals. In contrast to immunoaffinity chromatography, in immuno-ultrafiltration, the antibodies are used in non-immobilised form. Ochratoxin A was extracted with ACN/water (60/40, v/v), and the extract was loaded onto the ultrafiltration device. After a washing step with phosphate-buffered saline, containing 0.05% Tween 20, ochratoxin A was eluted with MeOH/acetic acid (99/1, v/v). The detection of ochratoxin A was carried out with high-performance liquid chromatography and a fluorescence detector coupled to an electrochemical cell (Coring cell). The electrochemical cell was used to eliminate matrix interferences by oxidising matrix compounds. The method was validated by repeatedly analysing spiked barley and rye samples as well as a certified wheat reference material. Recoveries and standard deviations (1 SD) were found to be 71 ± 9%, 77 ± 12% and 77 ± 8% in wheat, barley and rye, respectively. The limit of detection (S/N = 3) and limit of quantitation (S/N = 10) were determined to be 0.4 μg kg^-1 and 1 μg kg^-1. The analysis of the certified reference material resulted in ochratoxin A concentrations which were in the range assigned by the producer. Additionally, the effect of the electrochemical cell on other widely used clean-up techniques, namely the immunoaffinity clean-up and multifunctional columns (Mycosep #229), was evaluated. In all clean-up methods, an improvement of the chromatogram quality was registered.     

Heterogeneous Photocatalytic Degradation of Disulfoton in Aqueous TiO2 Suspensions: Parameter and Reaction Pathway Investigations

The photocatalytic degradation of organophosphorus insecticide disulfoton is investigated by having titanium dioxide (TiO₂) as a photocatalyst. About 99% of disulfoton is degraded after UV irradiation for 90 min. The effects of the solution pH, catalyst dosage, light intensity, and inorganic ions on the photocatalytic degradation of disulfoton are also investigated, as well as the reaction intermediates which are formed during the treatment. Eight intermediates have been identified and characterized through a mass spectra analysis, giving insight into the early steps of the degradation process. To the best of our knowledge, this is the first study reporting the degradation pathways of disulfoton. The results suggest that possible transformation pathways may involve in either direct electron or hole transfer to the organic substrate. The photodegradation of disulfoton by UV/TiO₂ exhibits pseudo‐first‐order reaction kinetics and a reaction quantum yield of 0.267. The electrical energy consumption per order of magnitude for photocatalytic degradation of disulfoton is 85 kWh/(m³ order).     

The Interplay of Photophysical Properties in Carbazole Fluorescent Oligomers

The photophysical properties and the organic synthesis using effective palladium‐catalyzed Suzuki coupling reactions from a series of carbazole derivatives are described and the relationships of the donor and acceptor groups are also investigated. The purification of the materials and its applications along with the corresponding photo‐physical characterizations were presented. With the advantages gained from 2D‐COSY spectra, which provide more correlated information between immediate atoms than ¹H‐NMR spectra and a series of further investigations were undertaken including powder X‐ray diffraction analysis, Infrared and Raman spectroscopy, constructing the composition conformation and chemical structure of the materials is more easily to achieve. Additionally, the optimized structure of the minimized energy geometries and spatial distributions of carbazole derivatives was calculated using density functional theory (DFT), new materials can be developed and designed selectively based on the method proposed in this work.     

Detection and Confirmation of Ginsenosides in Horse Urine by GC–MS and LC–MS

Ginseng has been used by the Chinese as a traditional herbal medicine for thousands of years. In view of the growing popularity in the use of ginseng preparations as natural remedies and food supplements worldwide, there is an increasing concern for their abuse in both human and animal sports. Ginsenosides are considered the major constituents of ginseng responsible for its pharmacological properties. In this study, a method was developed for the detection and confirmation of a number of ginsenosides in horse urine. The intact ginsenosides were detected and confirmed at 5–100 ng mL^?1 by LC–MS², and two deglycosylation metabolites, namely protopanaxadiol and protopanaxatriol, could both be detected and confirmed at 2 ng mL^?1 by GC–MS² after trimethylsilylation. The above GC–MS and LC–MS methods were then applied to study the in vitro metabolism of ginsenosides Rg1 and Rb1 and the in vivo urinary metabolites after oral administration of Rg1 to horses. Results obtained reveal the very first evidence for the existence of the metabolites, Rg1 and protopanaxatriol, as glucuronides in urine.     

The role of additives on dope rheology and membrane formation of defect-free Torlon hollow fibers for gas separation

The high demands on high performance membranes for energy, water and life science usages provide the impetus for membrane scientists to search for a comprehensive understanding of membrane formation from molecular level to design membranes with desirable configuration and separation performance. This pioneering work is to elaborate the importance of polymer rheology on hollow fiber formation and reveal the integrated science bridging polymer fundamentals such as polymer cluster size, shear and elongational viscosities, molecular orientation, stress relaxation to membrane microstructure and separation performance for gas separation. Torlon^® poly(amide imide) was employed in this study with various solvent/nonsolvent additives. The effects of additives on polymeric cluster size, hydrogen bonding and dope rheology during the phase inversion have been examined. It is found that hydrogen bonding and strain-hardening characteristics play very important roles in dope rheology and membrane separation performance. Torlon^® possesses strong hydrogen bonds with NMP/water mixtures, the addition of a small amount of water enlarges polymer cluster size, strengthen molecular network (i.e., strain hardening) and facilitate macrovoid-free morphology. However, strong hydrogen bonding may retard chain unfolding during spinning, induce faster relaxation for highly oriented dense-selective skin, and thus reduce gas-pair selectivity. By adjusting dope chemistry and spinning conditions with balanced solubility parameters and dope rheology, we have developed defect-free Torlon^® hollow fiber membranes with an O₂/N₂ selectivity of 8.55 and an ultra-thin layer of 488 Å simply using water as the additive. Fibers spun from dopes containing other additives have the optimal O₂/N₂ selectivity varying from 7.69 to 9.97 at 25 ± 2 °C, and the dense layer thickness varying from 500 Å to 2000 Å. Their corresponding mixed-gas O₂/N₂ selectivity for compressed air varies from 7.12 to 9.00.     

Orthogonal array optimization of microwave-assisted derivatization for determination of trace amphetamine and methamphetamine using negative chemical ionization gas chromatography–mass spectrometry

An orthogonal array design (OAD) was applied to optimize microwave-assisted derivatization (MAD) for analysis of trace amphetamine (AM) and methamphetamine (MA) by negative chemical ionization gas chromatography–mass spectrometry (NCI GC–MS). The 2,3,4,5,6-pentafluorobenzoyl chloride (PFBC) was used as a derivatization reagent. Experimental factors including solvent, microwave power, and irradiation time at four-levels were studied in 16 trials by OAD₁₆ (4⁴). The significance of these factors was investigated using analysis of variance (ANOVA) and percent contribution (PC). Solvent is statistically demonstrated a chief factor; microwave power and irradiation time are secondary factors. Under the optimum condition, calibration curve of AM is linear over a range from 0.01 to 100 ng mL⁻¹ with correlation coefficient 0.9988, and MA from 0.1 to 1000 ng mL⁻¹ with correlation coefficient 0.9951. The limit of detection (LOD) is 1.20 pg mL⁻¹ for AM and 13.04 pg mL⁻¹ for MA. An applicability of the method was tested by analyzing urine samples from amphetamine-type stimulants (ATS)-abusing suspects. Consequently, the OAD method not only optimizes the MAD condition for determination of trace AM and MA, but identifies the effects of factor solvent, microwave power and irradiation time on the MAD performance.     

N‐Heterocyclic Carbene Gold(I) Catalyzed Transformation of N‐Tethered 1,5‐Bisallenes to 6,7‐Dimethylene‐3‐azabicyclo[3.1.1]heptanes

Tying up loose ends : The reaction of bisallenes tethered with N‐(p‐tolylsulfonamide) in the presence of a cationic gold N‐heterocyclic carbene catalyst gave new cycloisomerization products, 6,7‐dimethyleneazabicyclo[3.1.1]heptanes, in high yields (see scheme; IPr=N,N′‐bis(2,6‐diisopropylphenyl)imidazol‐2‐ylidene).

     

Cooperative Recognition of a Copper Cation and Anion by a Calix[4]arene Substituted at the Lower Rim by a β‐Amino‐α,β‐Unsaturated Ketone

Chemodosimeter : Upon titration with Cu^II, the fluorescence of 1 showed strong fluorescence enhancement because the metal ion helps to lock the conformation of the fluorophores. Cu^II was reduced to Cu^I by the free phenolic OH group of 1 , the phenol was then oxidised by Cu^II and assisted in the trapping of Cu^I. Ditopic behaviour was observed for 1? Cu^I, which showed further enhancement of its fluorescence intensity upon complexation with anions (as depicted, A^?=CH₃COO^? or F^?).

     

Highly Elastic and Deformable Hydrogel Formed from Tetra‐arm Polymers

After decades of efforts by many researchers, we have succeeded in realizing a near‐ideal polymer network. This network, the Tetra network, is made by cross‐end‐coupling of tetra‐arm polymer modules. The mechanical energy dissipation was extremely low (tan δ ≈ 10⁻⁴). The macroscopic stress–strain relationship of the Tetra network was in good agreement with that of microscopic elastic blobs. The maximum breaking strength was extremely high (≥27 MPa). These results indicate that the Tetra network is closer to an ideal polymer network than any other conventional model networks. Because the Tetra network can be treated as uniformly packed elastic blobs, it should help apply the knowledge of single polymer chains seamlessly to the design of polymer materials and help further develop the theory of rubber elasticity.

     

Headspace‐single drop microextraction with a commercial capillary electrophoresis instrument

Automated coupling of headspace‐single drop microextraction (HS‐SDME) and CE has been demonstrated using a commercial CE instrument. When a drop hanging at the inlet tip of a capillary for CE is used as the acceptor phase, HS‐SDME becomes a simple but powerful sample pretreatment technique for CE before injection to facilitate sample cleanup and enrichment. By combining HS‐SDME with an on‐line sample preconcentration technique, large volume sample stacking using an electroosmotic flow pump, the sensitivity can be improved further. The overall enrichment factors for phenolic compounds were from 1900 to 3400. HS‐SDME large volume sample stacking using an electroosmotic flow pump was successfully applied to a red wine sample to obtain an LOD of 4 nM (0.8 ppb) for 2,4,6‐trichlorophenol which is a precursor for 2,4,6‐trichloroanisole causing the foul odor in wine called cork taint.