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Combination of hollow‐fiber‐supported liquid membrane and dispersive liquid–liquid microextraction as a fast and sensitive technique for the extraction of pesticides from grape juice followed by high‐performance liquid chromatography
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Vanessa Dutra Silva Vanessa Simão Adriana Neves Dias Jeferson Schneider Carletto Eduardo Carasek 《Journal of separation science》2015,38(11):1959-1968
The simultaneous use of a hollow‐fiber‐supported liquid membrane and dispersive liquid–liquid microextraction for the determination of pesticides directly in grape juice was investigated. The detection and quantification were performed by liquid chromatography with diode array detection. The optimum extraction condition was reached by filling the pores of the membrane wall with dodecanol and using hexane/acetone as extraction/dispersion solvents. Salt addition had a highly negative effect on the extraction efficiency and the optimum extraction time was 60 min. The volume of hexane/acetone mixture and the sample pH did not affect the signal at the levels studied. Therefore, an intermediate amount of these solvents (250 μL; 1:7.5 v/v) and pH 6 were selected. The optimum desorption condition was obtained with acetonitrile and 10 min of desorption time. The linear working range varied from 58 to 500 μg/L (parathion‐methyl), 62–500 μg/L (difenoconazole) and 107–500 μg/L (chlorpyrifos), with correlation coefficients ranging from 0.9980–0.9942. The limits of detection and quantification found were, respectively, 17 and 58 μg/L for parathion‐methyl, 19 and 62 μg/L for difenoconazole and 32 and 107 μg/L for chlorpyrifos. The relative standard deviation ranged between 3.5 and 11.2%. 相似文献
165.
Christian R. Noe M. Knollmüller K. Dungler C. Miculka P. Gärtner 《Monatshefte für Chemie / Chemical Monthly》1991,122(8-9):705-718
Summary Acetals3 and4 of alkylthienylcarbinols1 were prepared using an enantiomerically pure lactol2. In the key step these compounds were desulfurized. After deprotection the target compounds7 andent-7 were obtained.
Herrn Prof. Dr. H. Oelschläger zum 70. Geburtstag gewidmet 相似文献
166.
Bahia Abbas Moussa Hanaa M.A. Hashem Marianne Alphonse Mahrouse Sally Tarek Mahmoud 《Biomedical chromatography : BMC》2019,33(8)
Grapefruit juice inhibits esterase enzyme. Therefore, a possible interaction with ester prodrugs should be taken into consideration. In this study, the influence of grapefruit juice on sacubitril (SAC) rat liver S9 activation by esterase enzyme was evaluated. An RP‐HPLC method was developed and validated for estimation of SAC in rat liver S9 fraction using a C18 Cyano column as stationary phase and acetonitrile–sodium di‐hydrogen phosphate buffer (0.02 m , pH 4 adjusted by o‐phosphoric acid, 40:60, v/v), as mobile phase at a flow rate of 1 mL/min and UV detection at 254 nm. The method was successfully applied to an in vitro study in which SAC was incubated with rat liver S9 fraction prepared from rats that had previously ingested grapefruit juice for a week. The calculated SAC concentration after incubation was compared with that of SAC incubated with rat liver S9 fraction from the rat control group. The statistical significance between the results of test and control incubation sets was assessed. In conclusion, the current study demonstrated that grapefruit juice decreased SAC hydrolysis, hence delaying its activation to sacubitrilat (active form) in gut lumen. Based on this food–drug interaction, it may be required that grapefruit juice should be consumed with caution in patients receiving SAC. 相似文献
167.
Thomas Castaing-Cordier Dylan Bouillaud Dr. Paul Bowyer Dr. Olivier Gonçalves Prof. Patrick Giraudeau Dr. Jonathan Farjon 《Chemphyschem》2019,20(5):736-744
Benchtop NMR spectrometers experience a great success for a wide range of applications. However, their performance is highly limited by peak overlaps. Emerging “pure-shift NMR” (PS NMR) methods have been intensively used at high field to enhance the resolution by homodecoupling strategies. Here, different PS methods have been implemented on a compact NMR spectrometer operating at 43 MHz. Among the PS methods, the recent PSYCHE scheme appears more sensitive than Zangger-Sterk (ZS) experiments and offers a substantial resolution improvement as compared to 1D 1H. On the other hand, despite their slightly lower sensitivity, ZS methods are more efficient to reduce broad signals and are more immune to strong couplings. Finally, the classical J-resolved pulse sequence is more efficient to reduce larger signals for bigger-sized molecules. The three approaches appear relevant for benchtop NMR and their combination forms an efficient toolbox to analyze a great diversity of samples. 相似文献
168.
纳米孪晶纯铜的强度和导电性 总被引:2,自引:0,他引:2
强度和导电性是金属材料的两个至关重要的性能.常用的金属材料强化方式往往是在提高强度的同时使材料的导电性能明显损失,文章介绍了采用脉冲电解沉积技术制备出具有高密度孪晶片层结构的纯铜薄膜.这种具有纳米尺度的孪晶片层结构的纯铜材料不仅具有非常高的拉伸强度,同时还具有非常高的导电性.拉伸实验表明,当孪晶片层平均厚度小到15nm时,样品的拉伸屈服强度可达900MPa,断裂强度高达1068MPa(约为普通纯铜的10倍以上),并具有与无氧高导铜相当(97%IACS)的室温电导率. 相似文献
169.
Michel Franck-Neumann Michel Miesch Alain Cott Laurence Gross Bernard Metz 《Tetrahedron: Asymmetry》1993,4(12):2475-2482
The resolution of the cyclobutenic ester 1 using chiral lactols is described. After a stereospecific reaction sequence (cyclopropanation followed by an acidic solvolysis), the enantiomerically pure diquinanes 10 are obtained. 相似文献
170.
A. G. Savushkina 《Mathematical Notes》1996,60(1):68-80
The group of conjugating automorphisms of a free group and certain subgroups of this group, namely, the group of McCool basis-conjugating
automorphisms and the Artin braid group are considered. The Birman theorem on the representation of a braid group by matrices
is sharpened.
Translated fromMatematicheskie Zametki, Vol. 60, No. 1, pp. 92–108, July, 1996. 相似文献