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71.
Z H Liu W S Tu D R Li Y D Li C H Xie Y Z Yang B B Qin 《Biomedical chromatography : BMC》1990,4(2):83-86
A high performance liquid chromatographic (HPLC) method for the analysis of aflatoxin M1 (AFM1) in urine is described. Urine samples were treated with saturated lead acetate and AFM1 was extracted with chloroform. After washing with water to remove impurities the compound was derivatized with trifluoroacetic acid and the AFM1 derivative was analyzed quantitatively by HPLC. The sample pretreatment is simple and more selective. A good line correlation between AFM1 peak height and its concentration was obtained when AFM1 content was in the range of 50-400 pg. The ratio of recovery was 87.42%. Sensitivity is 0.01 ppb. The method is applicable to trace analysis. Results in urine of residents who live in the high/low liver cancer incidence area in Fushui county were the same as that of previous epidemiological investigation. 相似文献
72.
Claude Lavalle Alain Leborgne Nicolas Spassky Robert E. Prud'homme 《Journal of polymer science. Part A, Polymer chemistry》1987,25(5):1315-1328
β-(trichloromethyl)-β-propiolactone (CCl3-PL), β-(trifluoromethyl,methyl)-β-propiolactone (CF3, Me-PL) and β-(trifluoromethyl,ethyl)-β-propiolactone (CF3,Et-PL) have been obtained by the reaction of ketene with chloral, 1,1,1-trifluoroacetone and 1,1,1-trifluorobutanone, respectively. Chiral catalysis lead to optically active monomers. The enantiomeric excess of the lactones has been measured by 1H-NMR spectroscopy, in the presence of 2,2,2-trifluoro-1-(9-anthryl)ethanol or an europium chiral shift reagent. Polymerizations have been carried out in bulk or in toluene, at 60°C or 80°C, using mainly organometallic initiators. The Polymers become insoluble and crystalline at enantiomeric excesses over 80% for CCl3-PL and 70% for CF3,Me-PL. Melting temperatures were recorded from 238 to 268°C for poly(CCl3-PL) and from 78 to 100°C for poly(CF3,Me-PL), depending upon the molecular weight and the enantiomeric excess. The 13C-NMR specroscopy of poly(CCL3-PL) indicates that the polymerization of the corresponding lactone leads to polymers of increasing degrees of isotacticity with the enantiomeric excess of the monomer. 相似文献
73.
Adam Bange Jian Tu Xiaoshan Zhu Chong Ahn H. Brian Halsall William R. Heineman 《Electroanalysis》2007,19(21):2202-2207
A microbead based sandwich immunoassay for MS2 bacteriophage was developed using an interdigitated array (IDA) electrode with nanoscale dimensions (220 nm electrode width, 620 nm gap). The IDA was fabricated using an electron beam lithographic lift‐off technique. After an antibody‐assisted capture of MS2 using paramagnetic microbeads, a β‐galactosidase labeled secondary antibody was used to convert p‐aminophenyl‐β‐D ‐galactopyranoside (PAPG) into the redox active p‐aminophenol (PAP). Amperometric detection of PAP with IDA electrodes at +300 and ?200 mV vs. a Ag/AgCl reference electrode was used to measure the result, detecting MS2 concentrations as low as 10 ng/mL. 相似文献
74.
A non-aqueous reversed phase HPLC was developed for determining alpha-tocopherol in Sea buckthorn oil capsule without the need for saponification. A reversed phase column (Alltima C(18), 4.6 x 250 mm, 5 microm) was used with a mobile phase of methanol-acetonitrile (95 : 5, v/v) and flow rate of 1 ml/min. The contents in capsule were extracted with n-hexane. Detection wavelength was set at 292 nm. Each analysis requires no longer than 20 min. The linearity range for alpha-tocopherol was 9.4-47.0 microg/ml. The detection limit was 0.94 microg/ml. The mean recovery was 95.82 (RSD 2.3%). This method is suitable for quantitative analysis of alpha-tocopherol in Sea buckthorn oil or its Traditional Chinese Medicinal preparation. 相似文献
75.
The infrared emission of CO trapped in solid Ne and Ar is observed at low temperature. The first vibrational level of 12C16O is excited by a Q-switched frequency doubled CO2 laser. The emission spectrum consists of several lines arising from upper vibrational levels of 12C16O and also of 13C16O and 12C18O which are present in natural abundance. An interpretation is proposed which is based on the assumption that long range dipole—dipole interaction is the main physical process involved in these experiments. Resonance energy transfer produces an energy migration among 12C16O molecules without any change in vibrational populations. Phonon assisted energy transfer takes place between vibrational levels of the various isotopic species present in the solution. In order to satisfy the resonance condition a phonon is emitted or absorbed whose energy compensates for the energy mismatch between the transitions in each interacting molecule due to isotopic effect and or vibrational anharmonicity. The range of this process is greatly extended by energy migration. At the low phonon bath temperature phonon emission is much more probable than phonon absorption. So a strong excitation of upper vibrational levels with in some cases population inversions is observed.Molecular impurities act as efficient quenching centers even at very low concentration. When highly purified samples are used, the fluorescence decay time is found to be 20.6 ms in Ne and 14.5 ms in Ar and does not significantly depend upon concentration and temperature. It is concluded that radiationless relaxation is unimportant. 相似文献
76.
77.
Serganov A Yuan YR Pikovskaya O Polonskaia A Malinina L Phan AT Hobartner C Micura R Breaker RR Patel DJ 《Chemistry & biology》2004,11(12):1729-1741
Metabolite-sensing mRNAs, or "riboswitches," specifically interact with small ligands and direct expression of the genes involved in their metabolism. Riboswitches contain sensing "aptamer" modules, capable of ligand-induced structural changes, and downstream regions, harboring expression-controlling elements. We report the crystal structures of the add A-riboswitch and xpt G-riboswitch aptamer modules that distinguish between bound adenine and guanine with exquisite specificity and modulate expression of two different sets of genes. The riboswitches form tuning fork-like architectures, in which the prongs are held in parallel through hairpin loop interactions, and the internal bubble zippers up to form the purine binding pocket. The bound purines are held by hydrogen bonding interactions involving conserved nucleotides along their entire periphery. Recognition specificity is associated with Watson-Crick pairing of the encapsulated adenine and guanine ligands with uridine and cytosine, respectively. 相似文献
78.
Ur?ka L. ?tangar Urh ?ernigoj Polonca Treb?e Ksenija Maver Silvia Gross 《Monatshefte für Chemie / Chemical Monthly》2006,1(6):647-655
Transparent TiO2 films with a high photodegradation activity towards an azo dye in aqueous solution were prepared by sol–gel processing. Films
on soda–lime glass supports protected with a thin silica barrier layer exhibited better crystallization and monodisperse nanoparticles,
higher absorption of light below 370 nm, and higher photocatalytic activity than those films deposited on bare glass supports
proving the detrimental effect of interdiffused sodium ions on the development of the anatase nanostructure. The effect of
substrate was more pronounced in thinner films (300 nm) than in thicker ones (1200 nm), which were achieved by adding a template
(i.e. Pluronic F127) to the sol. 相似文献
79.
A very simple, selective and sensitive method was developed for the spectrophotometric determination of Mo in the presence of W. The method was based on the formation of color charge transfer complex, molybdotungstophosphate-3,3',5,5'-tetramethylbezidine anion, which was solubilized and stabilized in PVA medium. Following the recommended procedure, molybdenum could be determined in the linear range of 0.04-2.5 mug ml(-1) and the molar absorptivity was 1.47x10(4) l mol(-1) cm(-1) at 660 nm. The proposed method had been applied to the determination of trace molybdenum in tungsten ore with satisfactory results. 相似文献
80.
Yagüe S Terrón MC González T Zapico E Bocchini P Galletti GC González AE 《Rapid communications in mass spectrometry : RCM》2000,14(10):905-910
Some fractions of beer-factory wastewaters represent an important environmental concern owing to their high content of polyphenols and dark-brown color. The capacity of Coriolopsis gallica to preferentially degrade lignin has been successfully applied in our laboratory to the biotreatment and decolorization of paper-industry effluents. In this work, the ability of this white-rot fungus to degrade high-tannin-containing wastewaters is evaluated. Under all the conditions studied, effluent decolorization and chemical oxygen demand reduction achieved by C. gallica at day 12 of incubation were close to 50 and 65%, respectively. No adhesion of dark color to the fungal mycelium was observed suggesting that decolorization could be ascribed to C. gallica degradation systems. Mycelium dry-weight values showed that C. gallica is tolerant to relatively high tannin content present in the effluent samples. In the sample containing the highest effluent concentration (60% v/v), dry-weight values suggested an inhibition of fungal growth at day 6 of incubation and a further adaptation of the fungus to the stressing tannin effect at day 12 of fungal treatment. Pyrolysis/gas chromatography/mass spectrometry results showed a decrease of polyphenols pyrolysis products, mainly phenol and guaiacol, with the incubation time. All these results indicate the potential use of C. gallica in bioremediation of tannin-containing industrial wastewaters and in other applications where a reduction in polyphenols content is required. 相似文献