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991.
992.
L. A. Parry‐Jones S. M. Beldon P. D. Brimicombe D. Rodriguez‐Martin S. J. Elston 《Liquid crystals》2013,40(7):767-773
X‐ray diffraction studies are carried out in order to probe the smectic layer structure in liquid crystal devices filled with FLC mixture SCE8 and AFLC mixture CS4001, at a temperature just above the SmA?–SmC? phase transtion. The data gathered are time‐resolved in synchronization with a bipolar voltage pulse applied across the device. The layers are observed to move dynamically and reversibly with voltage application and removal, giving evidence for temporary vertical chevron formation due to the electroclinic effect on a timescale consistent with this phenomenon. 相似文献
993.
The steric effect of an aryloxido group on the synthesis and molecular structures of ytterbium aryloxides supported by β‐diketiminato ligand L (L = [N(2,6‐Me2C6H3)C(Me)]2CH?) is reported. Reactions of β‐diketiminatoytterbium dichloride, LYbCl2(THF)2, with NaOAr1 in THF (Ar1 = [2,6‐tBu2‐4‐MeC6H2], THF = tetrahydrofuran) at 60°C gave the corresponding ytterbium complexes LYb(OAr1)Cl(THF) ( 1 ) and LYb(OAr1)2 (1), depending on the molar ratio of dichloride to sodium aryloxide, respectively, while the same reactions with NaOAr2 and NaOAr3 (Ar2 = [2,6‐iPr2C6H3], Ar3 = [2,6‐Me2C6H3]) in 1:1 or 1:2 molar ratio in THF afforded only bisaryloxide complexes LYb(OAr2)2(THF) (1) and LYb(OAr3)2(THF) ( 4 ) in good yields, respectively. Complexes 1 , 2 , 3 , 4 were fully characterized, including X‐ray crystal structure analyses. All the complexes are efficient pre‐catalysts for the catalytic addition of amines to carbodiimides giving guanidines. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
994.
Shi‐jia Liu Ling Zhou Jun Zhang Chang‐yin Li Zi‐xiu Liu Wen‐zheng Ju 《Biomedical chromatography : BMC》2013,27(4):515-519
A highly sensitive liquid chromatography–tandem mass spectrometry method was developed and validated for the determination of limonin in beagle dog plasma using nimodipine as internal standard. The analyte and internal standard (IS) were extracted with ether followed by a rapid isocratic elution with 10 mm ammonium acetate buffer–methanol (26:74, v/v) on a C18 column (150 × 2.1 mm i.d.) and subsequent analysis by mass spectrometry in the multiple reaction monitoring mode. The precursor to product ion transitions of m/z 469.4 → 229.3 and m/z 417.2 → 122.0 were used to measure the analyte and the IS. The assay was linear over the concentration range of 0.625–100 ng/mL for limonin in dog plasma. The lower limit of quantification was 0.312 ng/mL and the extraction recovery was >90.4% for limonin. The inter‐ and intra‐day precision of the method at three concentrations was less than 9.9%. The method was successfully applied to pharmacokinetic study of limonin in dogs. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
995.
Ultra‐high pressure LC for astaxanthin determination in shrimp by‐products and active food packaging
A. Sanches‐Silva T. Ribeiro T. G. Albuquerque P. Paseiro R. Sendón A. Bernaldo de Quirós J. López‐Cervantes D. I. Sánchez‐Machado H. Soto Valdez I. Angulo G. P. Aurrekoetxea H. S. Costa 《Biomedical chromatography : BMC》2013,27(6):757-764
Nowadays, there is increasing interest in natural antioxidants from food by‐products. Astaxanthin is a potent antioxidant and one of the major carotenoids in crustaceans and salmonids. An ultra‐high pressure liquid chromatographic method was developed and validated for the determination of astaxanthin in shrimp by‐products, and its migration from new packaging materials to food simulants was also studied. The method uses an UPLC® BEH guard‐column (2.1 × 5 mm, 1.7 µm particle size) and an UPLC® BEH analytical column (2.1 × 50 mm, 1.7 µm particle size). Chromatographic separation was achieved using a programmed gradient mobile phase consisting of (A) acetonitrile–methanol (containing 0.05 m ammonium acetate)–dichloromethane (75:20:5, v/v/v) and (B) ultrapure water. This method was evaluated with respect to validation parameters such as linearity, precision, limit of detection, limit of quantification and recovery. Low‐density polyethylene films were prepared with different amounts of the lipid fraction of fermented shrimp waste by extrusion, and migration was evaluated into food simulants (isooctane and ethanol 95%, v/v). Migration was not detected under the tested conditions. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
996.
Ji‐Xin Tian Can Peng Lei Xu Yuan Tian Zun‐Jian Zhang 《Biomedical chromatography : BMC》2013,27(6):775-783
In this report, the in vitro metabolism of Strychnos alkaloids was investigated using liquid chromatography/high‐resolution mass spectrometry for the first time. Strychnine and brucine were selected as model compounds to determine the universal biotransformations of the Strychnos alkaloids in rat liver microsomes. The incubation mixtures were separated by a bidentate‐C18 column, and then analyzed by on‐line ion trap/time‐of‐flight mass spectrometry. With the assistance of mass defect filtering technique, full‐scan accurate mass datasets were processed for the discovery of the related metabolites. The structural elucidations of these metabolites were achieved by comparing the changes in accurate molecular masses, calculating chemical component using Formula Predictor software and defining sites of biotransformation based upon accurate MSn spectral information. As a result, 31 metabolites were identified, of which 26 metabolites were reported for the first time. These biotransformations included hydroxylation, N‐oxidation, epoxidation, methylation, dehydrogenation, de‐methoxylation, O‐demethylation, as well as hydrolysis reactions. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
997.
Tzu‐Chuan Huang Shih‐Ming Chen Yi‐Chieh Li Jen‐Ai Lee 《Biomedical chromatography : BMC》2013,27(9):1100-1106
Urinary d ‐lactate is highly correlated to diabetic nephropathy – a progressive kidney disease in renal glomeruli. In this study, we used a C3H/3e mouse model to investigate the relationship between urinary d ‐lactate and aristolochic acid nephropathy where the glomerular structure is not affected. The nephropathy was induced using intravenous injections of aristolochic acid at a dosage of 10 mg/kg per day for 5 days and was characterized biochemically and histologically. The urinary excretions of proteins, N‐acetyl‐β‐d ‐glucosaminidase and serum creatinine were determined and connected to histological conventional findings. Urinary d ‐lactate was analyzed using column‐switching high‐performance liquid chromatography with fluorescence detection. The results showed a remarkable increase of urinary markers, including of urinary proteins and N‐acetyl‐β‐d ‐glucosaminidase, and the histological examination confirmed a diagnosis of acute tubule necrosis. The ratio of d ‐lactate to creatinine in the urine of aristolochic acid‐treated mice was approximately 36 times greater than that of the mice in the control group (p < 0.05). The ratios for the two groups of mice were 311.00 ± 71.70 and 8.60 ± 1.80 µmol/mmol creatinine, respectively. These data confirm in vivo that urinary d ‐lactate reflects renal injury conditions in aristolochic acid‐treated mice and may be a marker for the assessment of nephropathy. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
998.
This study presents a new method for collecting and handling saliva samples using an automated analytical microsyringe and microextraction by packed syringe (MEPS). The screening and determination of lidocaine in human saliva samples utilizing MEPS and liquid chromatography–tandem mass spectrometry (LC‐MS/MS) were carried out. An exact volume of saliva could be collected. The MEPS C8‐cartridge could be used for 50 extractions before it was discarded. The extraction recovery was about 60%. The pharmacokinetic curve of lidocaine in saliva using MEPS‐LC‐MS/MS is reported. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
999.
Yong‐Bok Lee 《Biomedical chromatography : BMC》2013,27(11):1438-1443
A rapid, sensitive and stable high‐performance liquid chromatography (HPLC) method was developed and validated for the simultaneous determination of morniflumate and its major active metabolite, niflumic acid, in human plasma. HPLC analysis was carried out using a 5 µm particle size, C18‐bonded silica column with a mixture of acetonitrile and 0.005 m potassium phosphate monobasic in water (60:40, v/v) as the mobile phase and UV detection at 287 nm. The method involved the treatment with 50 μL of 0.4 m hydrochloric acid for the stability of morniflumate, extraction with diethylether and evaporation to dryness under a nitrogen stream. The lower limit of quantitation for morniflumate and niflumic acid was 50 and 500 ng/mL, respectively. The calibration curves for morniflumate and niflumic acid were linear over the concentration range of 50–20,000 ng/mL and 500–50,000 ng/mL, respectively, with correlation coefficients greater than 0.9995 and inter‐ or intra‐batch coefficients of variation not exceeding 13.79%. The variability (percentage difference) of incurred sample re‐analysis did not exceed 11.72% and all of the repeat samples fell within 20% of the mean value. This assay procedure was applied successfully to an examination of the pharmacokinetics of morniflumate and its metabolite, niflumic acid, in human subjects. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
1000.