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Abstract The changes in the characteristics of vibrational and optical properties of the conducting form of polypyrrole under pressure is studied. 相似文献
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Deoxynivalenol (DON), also known as vomitoxin, belongs to a class of naturally occurring mycotoxins produced by Fusarium spp. DON, 12, 13-epoxy-3,7 trihydroxytrichothec-9-en-8-one, is one of the most frequently detected mycotoxins in agricultural commodities worldwide. A method consisting of extraction, filtration, column cleanup, and RP-HPLC-UV separation and quantitation was validated for the determination of DON in grains (rice and barley), grain products (whole wheat flour, white flour, wheat germ, and wheat bran), and processed foods (bread, breakfast cereals, and pretzels). A 25 g test portion was extracted with 100 mL acetonitrile-water (84 + 16, v/v). After blending for 3 min, the supernatant was applied to a multifunctional column (MycoSep 225). The purified filtrate (2 mL) was evaporated to dryness and redissolved in the mobile phase. The toxins were then subjected to RP-HPLC-UV analysis. The accuracy and repeatability characteristics of the method were determined. Recoveries of DON added at levels ranging from 0.5 to 1.5 microg/g for all test matrixes were from 75 to 98%. SD and RSD(r) ranged from 0.7 to 11.6% and 0.9 to 12.7%, respectively. Within-laboratory HorRat values were from 0.1 to 0.7 for all matrixes analyzed. The method was found to meet AOAC method performance criteria for grains, grain products, and processed foods. The identity of DON in naturally contaminated test sample extracts was confirmed by HPLC/MS/MS analysis. 相似文献
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Ivleva VB Sapp LM O'Connor PB Costello CE 《Journal of the American Society for Mass Spectrometry》2005,16(9):1552-1560
Metastable decomposition of ions generated in matrix-assisted laser desorption/ionization (MALDI) mass spectrometers complicates analysis of biological samples that have labile bonds. Recently, several academic laboratories and manufacturers of commercial instruments have designed instruments that introduce a cooling gas into the ion source during the MALDI event and have shown that the resulting vibrational cooling stabilizes these labile bonds. In this study, we compared stabilization and detection of desorbed gangliosides on a commercial orthogonal time-of-flight (oTOF) instrument with results we reported previously that had been obtained on a home-built Fourier transform mass spectrometer. Decoupling of the desorption/ionization from the detection steps resulted in an opportunity for desorbing thin-layer chromatography (TLC)-separated gangliosides directly from a TLC plate without compromising mass spectral accuracy and resolution of the ganglioside analysis, thus coupling TLC and oTOF mass spectrometry. The application of a declustering potential allowed control of the matrix cluster and matrix adduct formation, and, thus, enhanced the detection of the gangliosides. 相似文献
4.
J. Arends H.J. Gassen A. Hegerath B. Mecking G. Nöldeke P. Prenzel T. Reichelt A. Voswinkel W.W. Sapp 《Nuclear Physics A》1984,412(3):509-522
Differential cross sections for the deuteron photodisintegration process were measured for photon energies between 200 and 440 MeV using the tagged photon beam facility of the Bonn 500 MeV synchrotron. At eight angles between 18° and 145° charged particles were detected simultaneously in time-of-flight spectrometers consisting of scintillation counters. Above the resonance region the measured cross sections agree fairly well with earlier results, whereas there are larger discrepancies at low photon energies. 相似文献
5.
R. J. Estep C. W. McCluskey B. A. Sapp 《Journal of Radioanalytical and Nuclear Chemistry》2008,276(3):737-741
In this report we describe the multiple isotope material basis set (MIMBS) method for isotope identification and show that
it can overcome limitations of ordinary response function fitting and the single isotope material basis set method (SIMBS)
when applied to ideal simulated NaI spectra, for an example attenuator and isotope library. Our simulations demonstrate that
ordinary response function fitting has difficult identifying isotopes when attenuation is a factor, and that the SIMBS method
can fail when multiple isotopes are present, so the more computationally intensive MIMBS method may be required for these
situations. Its effectiveness in analyzing more realistic spectra remains to be demonstrated. 相似文献
6.
Jordan D McIlvain T Alarcon R Beck R Bertozzi W Bhushan V Boeglin W Chen JP Dale D Dodson G Dolfini S Dow K Dzengeleski J Epstein MB Farkhondeh M Gilad S Görgen J Holtrop M Joo K Kelsey J Kim W Laszewski R Lourie R Mandeville J Margaziotis D Martinez D Miskimen R Papanicolas CN Penn S Sapp W Sarty AJ Tieger D Tschalaer C Turchinetz W Warren G Weinstein L Williamson S 《Physical review letters》1996,76(10):1579-1582
7.
Weinstein LB Baghaei H Bertozzi W Finn JM Glickman J Hyde-Wright CE Kalantar-Nayestanaki N Lourie RW Nelson JA Sapp WW Sargent CP Ulmer PE Cottman BH Ghedira L Winhold EJ Calarco JR Wise J Boberg P Chang CC Zhang D Aniol K Epstein MB Margaziotis DJ Perdrisat C Punjabi V 《Physical review letters》1990,64(14):1646-1649
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Urinary porphyrins are separated in a 72 cm x 50 microns I.D. fused-silica capillary by micellar electrokinetic capillary chromatography with 100 mM sodium dodecyl sulfate and 20 mM 3-(cyclohexylamino)-1-propanesulfonic acid at pH 11. Detection is accomplished by absorbance at 400 nm or fluorescence with excitation at 400 nm and emission at wavelengths above 550 nm. Substantial trace enrichment is found for porphyrins in urine samples or for porphyrin standards prepared without surfactant in the injection buffer. Limits of detection are in the 100 pmol/ml concentration range with an optimized fluorescence system. The method is shown suitable for the determination of porphyrins in clinical urine specimens. Comparisons are made between electrophoretic and chromatographic methods for the separation and detection of urinary porphyrins. 相似文献
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