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101.
Summary The analysis of several phenylurea herbicides in different waters is described using an immunoaffinity column clean-up and
determination by high performance liquid chromatography. The pesticides were selectively retained on a solid phase extraction
column containing antibodies to chlortoluron and to isoproturon immobilised onto silica. Selected phenylureas were eluted
using a simple phosphate buffered saline/ethanol mixture at low pH. The immunoaffinity approach gave extracts free of interfering
substances and allowed detection limits comparable to those required for pesticides in water in the European Community. The
proposed method was successfully applied to the determination of chlortoluron, isoproturon, linuron and chlorbromuron in tap
and river water.
Presented at the 21st ISC held in Stuttgart, Germany, 15th–20th September, 1996 相似文献
102.
液晶聚酯与环氧嵌段共聚物的合成及表征 总被引:5,自引:0,他引:5
近年来 ,人们利用高分子液晶作为热固性环氧树脂的改性剂 ,不仅可以提高环氧树脂的韧性和强度 ,而且可以改善其热性能 ,为制备高性能的环氧树脂提供了一条新的途径[1,2 ] .目前报道所使用的液晶聚合物大多为液晶聚酯[3 ] 或液晶性聚氨酯[4] ,这些液晶聚合物与环氧树脂由于存在相容性不好的问题 ,给其实际应用带来了困难 .为了改善二者的相容性 ,本文采用溶液法合成了末端带有反应活性基团的聚酯型液晶聚合物 ,将它再与双酚A环氧预聚物反应 ,制得了高分子液晶环氧嵌段共聚物 ,其合成路线如下 :2HOCOOCH3+ HO(CH2 ) 6 OH H… 相似文献
103.
A delayed coincidence method, time-interval analysis (TIA), has been applied to successive – decay events on the millisecond time-scale. Such decay events are part of the 220Rn216Po (T1/2 145 ms) (Th-series) and 219Rn215Po (T1/2 1.78 ms) (Ac-series). By using TIA in addition to measurement of 226Ra (U-series) from -spectrometry by liquid scintillation counting (LSC), two natural decay series could be identified and separated. The TIA detection efficiency was improved by using the pulse-shape discrimination technique (PSD) to reject -pulses, by solvent extraction of Ra combined with simple chemical separation, and by purging the scintillation solution with dry N2 gas. The U- and Th-series together with the Ac-series were determined, respectively, from alpha spectra and TIA carried out immediately after Ra-extraction. Using the 221Fr217At (T1/2 32.3 ms) decay process as a tracer, overall yields were estimated from application of TIA to the 225Ra (Np-decay series) at the time of maximum growth. The present method has proven useful for simultaneous determination of three radioactive decay series in environmental samples. 相似文献
104.
The volume and compressibility changes on mixing aqueous solutions of the amino acid and poly(ethylene glycol) were measured with a vibration densimeter and a sing-around velocimeter at 298.15 K. For the system of alanine-PEG-H2O, the additivity rule for the mean apparent molal volume and compressibility at infinite dilution held, and the excess volume and compressibility changes on mixing were obtained. For the system of glycine-PEG-H2O, the additivity rule for the mean apparent molal compressibility at infinite dilution did not hold. While the mean apparent molal volume and compressibility changes were negative and positive for the systems of another amino acid-PEG-H2O, respectively, where amino acids were valine, isoleucine, leucine, phenylalanine, and tryptophan. These results suggest that glycine and alanine are excluded from the hydration layer around PEG chain and the amino acids with a larger side chain than alanine are bound to the PEG chain due to the hydrophobic interaction. The hydration number per monomer around PEG chain was estimated to be 3.9. 相似文献
105.
Summary The net solvent effect for several solute-solvent pairs has been calculated by using the solvophobic approach for describing the liquid chromatographic process. For the same solutes and solvents the net solvent effect has been experimentally measured by using graphitized carbon black columns in GC and HPLC. A comparison between the measured and calculated values made in terms of normalized free energy changes, indicates that the solvophobic theory is fairly adequate for predicting the sequence of solvent strength and provides a comprehensive explanation of the various interactions occurring in reversed-phase LC. A critical discussion of the deviations of the theory from the experimental data is also presented.Presented at the 14th International Symposium on Chromatography London, September, 1982 相似文献
106.
The speed of sound u in and densities of eight binary mixtures of p-dioxane (p-C4H8O2) with methylcyclohexane (c-C6H11CH3), 1-chlorohexane (C6H13C1), 1-bromohexane (C6H13Br), p-xylene [C6H4(CH3)2], propylbenzene (C6H5C3H7), methyl acetate CH3COOCH3), butyl acetate (CH3COOC4H9), and amyl acetate (CH3COOC5H11) were measured over the whole composition range at 30°C. Isentropic compressibilities (K
S), Rao's molar sound functions (R), excess molar volumes (V
E), excess isentropic compressibilities (K
S
E
) together with relative change in volume V/12 values, have been obtained for all measured mole fractions. The excess partial molar volume (V1-V
1
0
) of p-dioxane in different solvents have also been estimated. The experimental results have been analyzed in terms of the Prigogine–Flory–Patterson theory of solutions. 相似文献
107.
热致液晶共聚酯酰胺/PET共混物的流变性能和原位增强特性 总被引:3,自引:1,他引:3
采用Instron3211型毛细管流变仪研究了PEA/PET共混物的流变性能,据此探讨共混物熔体的可纺性,讨论了共混物配比与复合纤维力学性能的关系,并且偏光显微镜,扫描电镜研究纤维的结构。结果表明,共混物的表观粘度低于PET的粘度,当PEA为10%,共混物的表观粘度达到最小值;且PEA含量低于10%时,共混物的可纺性即,表现出良好的原位增强效果。 相似文献
108.
A high sensitivity, multichannel fluorescence detector with small volume has been developed for capillary column liquid chromatography. Using an intensified linear photodiode array to monitor fluorescence emission, several important mixtures exhibiting native fluorescence have been examined following high efficiency separation on a capillary column. By correlating mass spectral, fluorescence spectral, and retention time data, information of potential utility in the structural elucidation of aromatic molecules contained in complex mixtures can be obtained. Examples include the separation and spectral examination of the polyaromatic compounds in samples of both biological and environmental interest. 相似文献
109.
一类新的毛细管气相色谱固定液—侧链液晶冠醚聚硅氧烷的研究 总被引:7,自引:0,他引:7
合成了一种新的毛细管气相色谱用固定液——侧链含冠醚液晶的聚硅氧烷,这种固定液易于涂渍在弹性石英毛细管柱上,柱效高,热稳定性好,极性中等,它具有高分子液晶和高分子冠醚固定液的双重保留性能,适于分离多种异构体。 相似文献
110.
《Arabian Journal of Chemistry》2022,15(10):104116
The misuses of veterinary drugs can result in the accumulation of residues in food of animal origin that can make its way to the final consumer. Herein we describe a simple method for the accurate determination of beta-lactams, quinolones, sulphonamides, and tetracyclines in fish, poultry, and red meat. No extraction cartridges were used; instead, the extraction process consisted of the addition of an organic solvents, shaking, centrifugation, and dilution. An extensive validation process demonstrated an excellent linearity (R2 ≥ 0.99) for 23-drug residues. The recovery of drugs in different matrices at two concentration levels (n = 6) was in the range of 82–119%. The method was proved to be repeatable and reproducible with intra/inter-day measurements (RSDs lower than 20%). The quantification limits of drug residues were in the range of 0.8 to 45.3 ug/kg, which is well below the maximum residue limits set by most regulatory authorities. This method was successfully applied to the routine analysis of 20 fish, poultry, and red meat samples (n = 60). 相似文献