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Shim, You-Shin,Kim, Seunghee,Seo, Dongwon,Park, Hyun-Jin,Ha, Jaeho Preston Publications 2014 Journal of Chromatographic Science Vol.52 No.7
<P>A rapid method for the determination of anthocyanin glucosides and free delphinidin in food using ultra-high-performance liquid chromatography (u-HPLC) was validated through tests of precision, accuracy and linearity. The u-HPLC separation was performed on a reversed-phase C18 column (particle size 2 ?m, i.d. 2 mm, length 100 mm) with a photodiode array detector. The limits of detection and quantification of the u-HPLC analyses ranged from 0.07 to 0.65 mg/kg for nine types of anthocyanin glucosides and from 0.08 to 0.26 mg/kg for delphinidin aglycone. The intra-day and inter-day precision of individual anthocyanin glucosides and delphinidin aglycone were less than 9.42%. All calibration curves showed good linearity (coefficient of determination = 0.99) within the tested ranges. The rapid and simultaneous u-HPLC method presented in this study significantly improved the speed, sensitivity and resolution of the analyses of nine types of anthocyanin glucosides and free delphidinin aglycone in grapes.</P>
Lee, Sooyeun,Choi, Hyeyoung,Kim, Eunmi,Choi, Hwakyung,Chung, Heesun,Chung, Kyu Hyuck Preston Publications 2010 Journal of analytical toxicology Vol.34 No.4
<P>The measurement uncertainty (MU) of methamphetamine (MA) and amphetamine (AP) was estimated in an authentic urine sample with a relatively low concentration of MA and AP using the bottom-up approach. A cause and effect diagram was deduced; the amount of MA or AP in the sample, the volume of the sample, method precision, and sample effect were considered uncertainty sources. The concentrations of MA and AP in the urine sample with their expanded uncertainties were 340.5 +/- 33.2 ng/mL and 113.4 +/- 15.4 ng/mL, respectively, which means 9.7% and 13.6% of the concentration gave an estimated expanded uncertainty, respectively. The largest uncertainty originated from sample effect and method precision in MA and AP, respectively, but the uncertainty of the volume of the sample was minimal in both. The MU needs to be determined during the method validation process to assess test reliability. Moreover, the identification of the largest and/or smallest uncertainty source can help improve experimental protocols.</P>
Fan, Li-Qun,Zhang, Yu-Ping,Gong, Wen-Jun,Qu, Ling-Bo,Lee, Kwang-Pill Preston Publications 2010 Journal of Chromatographic Science Vol.48 No.5
<P>Butyl-methacrylate-based porous monoliths were rapidly prepared in the fused-silica capillary with a 10-cm stripe of polyimide removed from its exterior. The photopolymerization could be carried out in 150 s using ethylene glycol dimethacrylate as a cross-linking agent; 1-propanol, 1,4-butanediol, and water as tri-porogenic solvents; and Irgacure 1800 as a photo-initiator. The effect of different morphologies on the efficiency and retention properties was investigated using pressure-assisted CEC (p-CEC), CEC, and low pressure-assisted liquid chromatography modes (LPLC). Baseline separation of the model analytes was respectively achieved including thiourea, toluene, naphthalene, and biphenyl with the lowest theoretical height up to 8.0 microm for thiourea in the mode of p-CEC. Furthermore, the influence of the tri-porogenic solvents on the morphology of methacrylate-based monoliths was systematically studied with mercury intrusion porosimetry and scanning electron microscopy.</P>
Lee, Bokyoung,Hwangbo, Yown,Lee, Dong Soo Preston Publications 2009 Journal of Chromatographic Science Vol.47 No.7
<P>A method has been developed for the determination of the concentration of low molecular weight monocarboxylic acid gases in the atmosphere. The method involves quantitative collection of analyte gases using a parallel plate diffusion scrubber and subsequent ion analysis by ion chromatography. Among the gases are formic acid, acetic acid, propionic acid, n-butyric acid, and n-valeric acid. Method detection limits are on the order of sub to low parts-per-trillion by volume. The method has been successfully applied to ambient air analysis.</P>
Lee, Kyeong-Ryoon,Song, Jin Sook,Chae, Yoon-Jee,Kim, Min-Sun,Choi, Sung-Heum,Jeon, Dong Ju,Bae, Myung Ae,Ahn, Sung-Hoon Preston Publications 2013 Journal of chromatographic science Vol.51 No.6
<P>A method for assaying a novel phosphodiesterase-4 inhibitor, 2-aryl-7(3',4'-dialkoxyphenyl)-pyrazolo [1,5-alpha] pyrimidine (PDE-310), was developed and validated in rat plasma using liquid chromatography-tandem mass spectrometry (LC-MS-MS). Rat plasma samples were processed by liquid-liquid extraction with ethyl acetate and injected onto the LC-MS-MS system for quantification. PDE-310 and imipramine (i.e., internal standard) were separated using a Gemini C18 column with mixture of acetonitrile and 0.1% formic acid (70:30, v/v) as the mobile phase. The ion transitions monitored were m/z 425.0 331.0 for PDE-310 and m/z 281.3 86.1 for imipramine in the multiple-reaction monitoring mode. The detector response was specific and linear for PDE-310 concentrations in the range of 0.1-50 ?g/mL. The intra-day and inter-day precision and accuracy of the method were determined to be within the acceptance criteria for assay validation guidelines. The recoveries were approximately 85.7 and 88.2% from rat plasma for PDE-310 and imipramine, respectively. PDE-310 was stable under various processing and handling conditions. PDE-310 concentrations were readily measured in rat plasma samples up to 8 h after an intravenous administration of PDE-310, suggesting that the assay is practically useful.</P>
Park, Hyun-Mee,Hong, Soon-Min,Agustin-Camacho, M R,Dirwono, Warnadi,Lee, Kang-Bong Preston Publications 2009 Journal of chromatographic science Vol.47 No.8
<P>Pressurized liquid extraction (PLE) system was optimized to simultaneously determine polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) in soil samples by gas chromatography with time-of-flight mass spectrometry. PLE parameters (temperature, pressure, static time, and flush volume) and packing materials (activated copper and sorbents such as: Florisil, silica gel, and a combination of Florisil and silica gel) were studied to achieve a one-step extraction and cleanup that could be analytically rapid and reliable. Method detection limit was found to be in the range of 0.1-0.4 mg/kg for PCBs and 0.1-0.6 mg/kg for PBDEs with a relative standard deviation of 1.7-7.3% for PCBs and 2.6-6.3% for PBDEs. A standard reference material for PCBs, NIST-SRM 1939a, spiked with PBDEs standard, was analyzed to substantiate the validity of the optimized method. Experimental values agreed well with the certified values with recoveries of 71.6-117%, and the optimized PLE system has been proven to be useful for the simultaneous determination of PCBs and PBDEs with various congeners in soil samples.</P>