Multiresidue analysis of pesticides with hydrolyzable functionality in cooked vegetables by liquid chromatography tandem mass spectrometry

It would be preferable for pesticide residues substituted by hydrolyzable functionality to be analyzed after cooking because their structures are apt to degrade during boiling and/or heating. A liquid chromatography–tandem mass spectrometry (LC‐MS/MS) method for the quantitative determination of 44 pesticide residues with hydrolyzable functional group in five typical vegetable widely consumed in Republic of Korea is described. The sample clean‐up was carried out according to the method of Food Code No. 83 established by the Korea Food and Drug Administration (KFDA). Zorbox XDB‐C₁₈ column was selected for the analysis because of the best peak separation. The LC mobile phase consisted of water and 5 mm methanolic ammonium formate, which resulted in a peak shape with good symmetry at each run. Tandem mass spectroscopic (MS/MS) experiments were performed in ESI positive mode and the multiple reaction monitoring modes. A conventional matrix effect was modified to more comprehensive form 100γ_ij (%). A high matrix effect (相似文献   

Effects of surfactant and molecular weight of polyol on grating formation and switching of holographic PDLC

The interposition of surfactants between polymer and liquid crystal (LC) droplets was theoretically predicted by the positive spreading coefficient (0 < λ₃₁) and utilized to interpret the morphology, grating formation kinetics, diffraction efficiency, and switching of the holographic polymer dispersed liquid crystal (HPDLC), prepared from various types (octanoic acid, poly oxyethylene octyl phenyl ether, and perfluoro‐1‐butanesulfonyl fluoride) and amounts (0–9 wt%) of surfactant and molecular weights of polyol (PPG). Regardless of the surfactant type, diffraction efficiency increased with the addition and increasing amount of surfactant, a tendency consistent with increasing value of spreading coefficient, which is determined by the formulations of grating formation. In contrast, diffraction efficiency showed a maximum with the polypropylene glycol (PPG) molecular weight. Surfactant effectively reduced the anchoring energy and electrically drove the film which otherwise was not driven. Overall, surfactant with greater λ₃₁ gave smaller droplet, greater diffraction efficiency, driving voltage, contrast ratio, and smaller response time. Copyright © 2008 John Wiley & Sons, Ltd.     

Preparation and characterization of crosslinked cellulose/sulfosuccinic acid membranes as proton conducting electrolytes

A series of crosslinked polymer electrolyte membranes were prepared by blending cellulose and sulfosuccinic acid (SA) for fuel cell applications. The crosslinking reaction of membranes occurred via the esterification between –OH of cellulose and –COOH of SA, as confirmed by FT-IR spectroscopy. Both the ion exchange capacity and the proton conductivity increased in proportion to the increase of SA concentrations due to the increasing portion of charged groups in the membrane. In contrast, the water uptake linearly increased up to 25 wt.% of SA concentration, above which it decreased abruptly. The maximum behavior of water uptake may be a result of competitive effect between the increasing number of ionic sites and the increasing degree of crosslinking with the SA concentrations. Wide angle X-ray scattering also showed that the crystalline structures of cellulose disappeared upon the introduction of SA. The mechanical properties of cellulose/SA membranes, i.e., tensile strength at break and Young’s modulus, showed a maximum at 15 wt.% of SA, as revealed by universal testing machine. These membranes exhibited good thermal stability up to 250 °C, as revealed by thermal gravimetric analysis.     

Dynamic DSC Characterization of Epoxy Resin by Means of the Avrami Equation

A phenomenological approach was used to characterize the cure processes of epoxy resins (a diglycidyl ether of bisphenol A and its modifier CTBN) from dynamic experiments by DSC. Various kinetic parameters were obtained by using a modified Avrami expression. The resulting overall activation energies for the two systems agreed very well with the published data in the whole cure temperature range. In contrast with the isothermal results and the general dynamic models, a change in the exponent and the non-linear temperature dependence of the rate constant were also observed.This revised version was published online in November 2005 with corrections to the Cover Date.     

Synthesis of Pd-CNT nanocomposites and investigation of their catalytic behavior in the hydrodehalogenation of aryl halides

A catalytic system based on Pd-CNT nanocomposites for the hydrodehalogenation of aryl halides is described. Thiol groups were utilized as linkers to secure the Pd nanoparticles without agglomeration. The Pd-CNT nanocomposites effectively promoted the hydrodehalogenation of aryl halides at a low Pd content (∼2.3%) and in the absence of any ligand. The results suggest that the CNTs could significantly influence the catalytic activities of CNT-supported metal catalysts for hydrodehalogenation.     

BIOLUMINESCENCE OF ACETALDEHYDE CATALYZED BY BACTERIAL LUCIFERASE

Abstract— Bioluminescence from the oxidation of acetaldehyde by bacterial luciferase of Photobacterium fischeri has been demonstrated for the first time and its efficiency has been compared with that of nonanal and other short chain aldehydes.     

Field‐effect transistors based on PPV derivatives as a semiconducting layer

A series of modified thiophene groups containing PPV‐based semiconducting materials, poly[(2,5‐bis(octyloxy)‐1,4‐phenylenevinylene)‐alt‐(2,2′bithienylenevinylene)] ( PPBT ), poly[(2,5‐bis(octyloxy)‐1,4‐phenylenevinylene)‐alt‐(5,5‐thiostilylenevinylene)] ( PPTVT ), have been synthesized through a Horner coupling reaction. From the FTIR and ¹H NMR spectroscopy, the configuration of the vinylene groups in the polymers was all trans (E) geometry. The weight‐average molecular weights (M_w) of PPBT and PPTVT were found to be 11,700 and 11,800, with polydispersity indices of 2.51 and 2.53, respectively. PPBT and PPTVT thin films exhibit UV–visible absorption maxima at 538 and 558 nm, respectively, and the strong absorption shoulder peaks at 578 and 602 nm, respectively. Solution processed field‐effect transistors (FET) fabricated using all the polymers showed p‐type OTFT characteristics. The field‐effect mobility of the PPTVT was obtained up to 2.3 × 10^?3 cm² V^?1 s^?1, an on/off ratio of 1.0 × 10⁵ with ambient air stability. Studies of the atomic force microscopy (AFM) and X‐ray diffraction (XRD) analysis of the polymer thin films revealed that all the polymers were amorphous structure. The greater planarity and rigidity of PPTVT compared to PPBT results in elongation of conjugation length and better π–π stacking of polymer chains in amorphous region, which leads to improved FET performance. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 111–120, 2009     

HPLC determination of irbesartan in human plasma: its application to pharmacokinetic studies

A simple and rapid HPLC method using fluorescence detection was developed for determination of irbesartan in human plasma. Sample preparation was accomplished through a simple deproteinization procedure with 0.4 mL of acetonitrile containing 800 ng/mL of losartan (internal standard), and to a 0.1 mL plasma sample. Chromatographic separation was performed on a Zorbax Xclipse XDB C₁₈ column (150 × 4.6 mm, i.d., 5 µm) at 40°C. An isocratic mobile phase, acetonitrile:0.1% formic acid (37:63, v/v), was run at a flow‐rate of 1.0 mL/min, and the column eluent was monitored using a fluorescence detector set at excitation and emission wavelengths of 250 and 370 nm, respectively. The retention times of irbesartan and losartan were 4.4 and 5.9 min, respectively. This assay was linear over a concentration range of 10–5000 ng/mL with a lower limit of quantification of 10 ng/mL. The coefficient of variation for this assay precision was less than 8.48%, and the accuracy exceeded 94.4%. The mean relative recoveries of irbesartan and losartan were 98.4 and 99.1%, respectively. This method was successfully applied for pharmacokinetic study after oral administration of irbesartan (300 mg) to 23 Korean healthy male volunteers. Copyright © 2009 John Wiley & Sons, Ltd.