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91.
Continuous flow microextraction combined with high-performance liquid chromatography for the analysis of pesticides in natural waters 总被引:2,自引:0,他引:2
Continuous flow microextraction (CFME) combined with high-performance liquid chromatography-ultraviolet (HPLC-UV) detection has been applied to the analysis of five widely used pesticides, simazine, fensulfothion, etridiazole, mepronil and bensulide, present at trace levels in water samples. CFME employs a single organic solvent drop positioned at the tip of a polyether ether ketone (PEEK) tubing, which is immersed in a continuous flowing aqueous sample solution in a 0.5-ml glass chamber. The PEEK tubing acts as the organic drop holder and fluid delivery duct. Analytes are partitioned between the organic drop and the bulk sample solution. Important extraction factors including type of solvent, its volume, sample solution flow rate, extraction time, its pH and addition of salt were investigated. All pesticides exhibit good linearity in the investigated concentration range of 25-250 ng ml(-1) with coefficients of determination (R2) ranging from 0.9879 to 0.9999 under the optimized conditions. Detection limits lower than 4 ng ml(-1) were obtained for all analytes. The method was evaluated by analyzing natural water sample collected from a reservoir in Singapore. This study for the first time demonstrated the compatibility of CFME procedure and HPLC separation. 相似文献
92.
Sang‐Hoon Ji Wan Pyo Hong Seung Ho Ko Kee‐Jung Lee 《Journal of heterocyclic chemistry》2006,43(3):799-801
A new synthesis of 4‐carbomethoxynaphtho[2,1‐c]isoxazoles 4a‐d from methyl 3‐(alkynylphenyl)‐2‐nitromethyl‐2‐propenoates 2a‐d by the intramolecular nitrile oxide cycloaddition is described. The latter are readily obtained from 2‐alkynylbenzaldehydes through the Baylis‐Hillman adduct acetates 1a‐d followed by nucleophilic substitution of nitrite anion. 相似文献
93.
Effects of Cu2−xS phase removal on surface potential of Cu2ZnSnS4 thin-films grown by electroplating
Gee Yeong Kim Ju Ri Kim William Jo Kee Doo Lee Jin Young Kim Trang Thi Thu Nguyen Seokhyun Yoon 《Current Applied Physics》2014,14(12):1665-1668
Cu2ZnSnS4 (CZTS) has an optical band gap of 1.4–1.5 eV, which is similar to that of Cu(In,Ga)Se2 (CIGS), and a high absorption coefficient (>104 cm−1) in the visible light region. In previous reports, CIGS thin-film solar cells have been shown to improve the performance of the device since the secondary phase is removed by Potassium cyanide (KCN) etching treatment. Therefore, in this study we applied a KCN etching treatment on CZTS and measured the effects. We confirmed the removal of Cu2−xS via Kelvin probe force microscopy (KPFM) and Raman scattering spectroscopy. The effects of the experiment indicate that we can define with precision the location of the secondary phases, and therefore the control of the secondary phases will be easier and more efficient. Such capabilities could improve the solar cell performance of CZTS thin-films. 相似文献
94.
Seung Wha Lee Sang Hoon ChaHwan Hoon Chung Kee Hwan KimSuk Keu Yeom Bo Kyung SeoBo Kyung Je Baek Hyun Kim 《Magnetic resonance imaging》2014
Purpose
To describe the patterns of bile distribution in the biliary tree, duodenum, jejunum, and stomach, and to determine the gallbladder ejection fraction (GBEF) by using functional magnetic resonance cholangiography (MRC) with gadolinium-ethoxybenzyl-diethylenetriamine penta-acetic acid (Gd-EOB-DTPA) in healthy volunteers.Materials and Methods
Forty subjects were included in this study. After conventional MRC, pre-fatty meal MRC (PRFM) was obtained at 30, 40, 50, and 60 min after contrast agent injection. Then, post-fatty meal MRC (POFM) was obtained every 10 min for 1 h. We assessed the PRFM and POFM for opacification of contrast agent in the first- and second-order intrahepatic ducts (IHDs) and the common bile duct (CBD). Contrast agent opacification in the cystic duct was assessed, and the percentage volume of contrast agent filling in the gallbladder (GB) was calculated on PRFM. We calculated the GBEF and assessed the presence of contrast agent in the GB, duodenum, jejunum, and stomach.Results
Thirty-six (90%) subjects showed grade 3 CBD opacification (visible contrast and well-defined bile duct border) on 60-min PRFM. Thirty-four (85%) subjects showed grade 3 first-order IHD opacification on 60-min PRFM. All (100%) subjects showed cystic duct opacification of contrast agent, and the average percentage volume of contrast agent filling in the GB was 68.81% ± 16.84% on 60-min PRFM. The GBEF at 30-min POFM was 35.00% ± 18.26%. Ten (25%) subjects had no contrast agent in the stomach and small bowel on all PRFMs. Twelve (30%) subjects had contrast medium in the stomach on PRFM and/or POFM.Conclusions
Functional MRC with Gd-EOB-DTPA can allow determining the distribution of bile in the biliary tree and small intestine, as well as the GBEF. 相似文献95.
de Prinse Thomas Klantsataya Elizaveta Tsiminis Georgios Payten Thomas Moffatt Jillian Kee Tak W. Spooner Nigel A. 《Journal of fluorescence》2022,32(3):1051-1057
Journal of Fluorescence - Acetone and butanone were seen to emit blue light around 450 nm when excited in the green by a high intensity pulsed laser. The pathway of this anti-Stokes... 相似文献
96.
97.
An ultra high‐performance liquid chromatographic (UHPLC) system was developed and optimized for the separation of porphyrins of clinical interest. Optimum conditions for the simultaneous separation of uroporphyrin, hepta‐, hexa‐, penta‐carboxylic acid porphyrins and coproporphyrin and their type I and III isomers on a Thermo Hypersil BDS C18 column (2.4 µm particle size, 100 × 2.1 mm i.d.) using a gradient elution with 10% (v/v) acetonitrile in 1.0 m ammonium acetate buffer (pH 5.16) and 10% (v/v) acetonitrile in methanol at a flow‐rate of 0.4 mL/min. The effect of mobile phase buffer molarity on the sensitivity of fluorescence detection and resolution of porphyrin isomers was investigated. The method was successfully applied to the analysis of porphyrins extracted from the urine and faeces of patients with various human porphyrias. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
98.
Chun SH Chai YS Jeon BG Kim HJ Oh YS Kim I Kim H Jeon BJ Haam SY Park JY Lee SH Chung JH Park JH Kim KH 《Physical review letters》2012,108(17):177201
We find the realization of large converse magnetoelectric (ME) effects at room temperature in a magnetoelectric hexaferrite Ba0.52Sr2.48Co2Fe24O41 single crystal, in which rapid change of electric polarization in low magnetic fields (about 5 mT) is coined to a large ME susceptibility of 3200 ps/m. The modulation of magnetization then reaches up to 0.62μ(B)/f.u. in an electric field of 1.14 MV/m. We find further that four ME states induced by different ME poling exhibit unique, nonvolatile magnetization versus electric field curves, which can be approximately described by an effective free energy with a distinct set of ME coefficients. 相似文献
99.
Ruijin Yu Hongjuan Li Hailong Ma Caifeng Wang Huan Wang Byung Kee Moon Jung Hyun Jeong 《Journal of luminescence》2012,132(10):2783-2787
A thiogallate chalcogenide phosphor CaLaGa3S7:Eu2+ was synthesized by a solid-state reaction at 950 °C in a H2S atmosphere. The photoluminescence excitation,emission spectra, concentration quenching, fluorescence lifetime, and thermal quenching process of the phosphor were investigated in detail. It was found that the synthesized phosphor emitted intense and broadband yellowish-green light with a peak at 554 nm. Thus, the proposed phosphor is suitable for the development of blue or near UV LED. The critical dopant concentration of Eu2+ (Rc=15 Å) per unit formula was found to be 0.15 mol. At room temperature, the fluorescence lifetime of Eu2+ in CaLaGa3S7 was found to be 0.216 μs. The activation energy for thermal quenching was 0.29 eV. The chromaticity coordinates of our phosphor is very close in color to Y3Al5O12:Ce3+. Therefore, CaLaGa3S7:Eu2+ can be a good alternative as a yellowish-green phosphor and can be used for white light generation in phosphor-converted LEDs. 相似文献
100.
Sangsoo Lim Seul Kee Byeon Ju Yong Lee Myeong Hee Moon 《Journal of mass spectrometry : JMS》2012,47(8):1004-1014
A qualitative analysis tool (LiPilot) for identifying phospholipids (PLs), including lysophospholipids (LPLs), from biological mixtures is introduced. The developed algorithm utilizes raw data obtained from nanoflow liquid chromatography–electrospray ionization–tandem mass spectrometry experiments of lipid mixture samples including retention time and m/z values of precursor and fragment ions from data‐dependent, collision‐induced dissociation. Library files based on typical fragmentation patterns of PLs generated with an LTQ‐Velos ion trap mass spectrometer are used to identify PL or LPL species by comparing experimental fragment ions with typical fragment ions in the library file. Identification is aided by calculating a confidence score developed in our laboratory to maximize identification efficiency. Analysis includes the influence of total ion intensities of matched and unmatched fragment ions, the difference in m/z values between observed and theoretical fragment ions, and a weighting factor used to differentiate regioisomers through data filtration. The present study focused on targeted identification of particular PL classes. The identification software was evaluated using a mixture of 24 PL and LPL standards. The software was further tested with a human urinary PL mixture sample, with 93 PLs and 22 LPLs identified. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献