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A rapid method for the derivatization of phenolic antioxidants using microwave irradiation has been developed. Six antioxidatively active phenolic components of wines and fruits, namely gallic acid, gentisic acid, vanillic acid, caffeic acid, ferulic acid and p-coumaric acid were used in the model study. The solution of phenolic acids was evaporated to dryness on a rotary evaporator followed by further drying under microwave irradiation (600 W, 30 s). The resultant residue was dissolved in pyridene and treated with bis(trimethylsilyl)acetamide while irradiated by microwave using high power for 30 s. Controlled reaction was carried out employing bis(trimethylsilyl)trifluoroacetamide under conventional heating for 30 min. The trimethylsilyl derivatives were identified and quantified on a gas chromatography/mass selective detector. The mass spectral fragmentation patterns of the derivatives obtained by microwave irradiation were identical to those prepared by heating. The yields of microwave-assisted silylation were comparable to those from conventional heating. The rsd were less than 8% for six replicates. The linearity in wine matrix was nearly perfect. This method is a useful protocol to examine the phenolic constituents in wines and agricultural products. 相似文献
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在现有方法基础上对沉积物中磺胺类、喹诺酮类、大环内脂类和四环素类抗生素的提取、富集、净化以及仪器分析方法进行了优化。以EDTA-Mcllvaine缓冲溶液与乙腈(V:V,1:1)混合液作为提取液,利用超声波细胞破碎仪进行超声提取,串联强阴离子交换柱(SAX)和HLB固相萃取柱进行固相萃取(SPE),通过超高效液相/串联质谱(UPLC-MS/MS)测定沉积物中抗生素的含量。抗生素基质加标回收率在56.4%~110%,相对标准偏差为1.1%~24.3%,方法检出限0.0055~0.716 ng/g。本方法有效地提高了沉积物中抗生素的提取效率,并应用于实际样品的测定中。 相似文献
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Reaction solutions of selectfluor (1) with triphenylethylene (4a) and tetraphenylethylene (4b) were monitored by ESI-MS and ESI-MS/MS. Detection and characterization of the key radical cationic intermediates 5a.+ and 5b.+) fully supports the SET mechanism in electrophilic fluorination as depicted above. [reaction: see text] 相似文献
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[structure: see text] Remarkable UV OLED devices using novel spiro-configured bifluorenes as UV emitters have been successfully achieved with external quantum efficiencies up to 2.6-3.1% and emission wavelengths as short as 370 nm. In addition, these large-gap materials have been shown to be effective hosts for red phosphorescent emitters in phosphorescent OLEDs. This result represents the first example that pure hydrocarbon molecules can serve as an efficient host for red electrophosphorescence devices. 相似文献