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971.
本文报道了傅烷基磷酸钍的结构分析,证实了该材料具有类似于α-磷酸锆的层状结构;并将其应用于气相色谱固定相,较好地实现了硫醇类、含氯烃类及芳香烃类混合样品的分离。 相似文献
972.
JunJiaoYANG KaiZHANG RuYuGAO YuKuiZHANG ChaoYAN 《中国化学快报》2004,15(4):435-438
A novel monolithic stationary phase having long alkyl chain ligands was introduced and evaluated in pressurized-capillary electrochromatography of small neutral and charged compounds.The monolithic column was prepared by the in situ copolymerization of ethylene dimethacrylate,1-hexadecene,allyl alcohol and 2-acrylamido-2-methyl-l-propanesulfonic acid in a quaternary porogenic solvent mixture consisting of 1,4-butanediol,cyclohexanol,dodecanol and water. 相似文献
973.
974.
975.
溶胶-凝胶毛细管气相色谱柱热稳定性的考察 总被引:13,自引:0,他引:13
溶胶—凝胶毛细管气相色谱柱是一类新型的色谱柱。通过与静态法涂渍并用自由基引发交联使固定相固载化的色谱柱比较,溶胶—凝胶色谱柱除了具有制作工艺简单、分离效果好等特点外,还具有很好的热稳定性和溶剂稳定性。其工作温度可高于400℃。 相似文献
976.
Paul V. Doskey 《Journal of separation science》1991,14(11):724-728
A comparison has been made between two cryogenic preconcentration - high resolution gas chromatography techniques for the analysis of non-methane hydrocarbons in ambient air, one involving treatment of air samples with magnesium perchlorate to remove water, the other involving analysis without treatment. Recoveries of C1-, C2-, and C3-substituted benzenes in treated samples were 80%, 50%, and 50%, respectively. Incomplete recovery of C7-C9 n-1-olefins was also observed. C2-C8 hydrocarbons and C2-C6 n-1-olefins were recovered with greater than 90% efficiency. Analyses of certified audit samples containing a mixture of C2-C8 aliphatic and aromatic hydrocarbons at the 20 ppbv level in humidified zero-grade air indicated that the accuracy of the technique for untreated air samples was approximately 90%. The use of magnesium perchlorate for water removal cannot be recommended for the analysis of non-methane hydrocarbons in ambient air. 相似文献
977.
Electrospray ionization mass spectrometry of multiply charged biopolymer ions of different molecular size revealed a strong influence of tuning parameters on their detectability in quadrupole ion trap and triple quadrupole mass spectrometers. Hence, after optimizing the ion optical parameters with the signal of the 4- charge state of (dT)(24) (low charge state tuning), a tenfold increase in the signal-to-noise ratio for a mixture of oligodeoxythymidylic acids (n = 12-18) was obtained compared with the results achieved with tune parameters optimized with a synthetic 80-mer oligodeoxynucleotide. By contrast, a detection limit in the upper femtomole region could only be reached for a 104-mer oligodeoxynucleotide utilizing the 24- charge state of the 80-mer (high charge state tuning). The same effect was observed for proteins investigated in the positive ion mode using low and high charge states of cytochrome c and carbonic anhydrase, respectively, for instrument tuning. By comparing the settings for low and high charge state tuning, it became obvious that the most significant difference was observed in the potential applied to the heated metal capillary used to transfer ions from the atmospheric pressure to the vacuum region of the ion source. Taking advantage of the optimized tuning procedure, the molecular mass of a 61 base pair product of polymerase chain reaction was accurately determined by electrospray ionization mass spectrometry on-line interfaced to ion-pair reversed-phase high-performance liquid chromatography. 相似文献
978.
Roberto Barcarolo 《Journal of separation science》1990,13(7):465-469
This paper describes the use of coupled LC-GC for the determination of organochlorine pesticide residues in fat samples. Organochlorine pesticide residues are preseparated from fat by LC on a short C-18 column using an organic solvent as the mobile phase. Evaporation of the LC eluent is achieved by a modified on-column interface, introducing an on-line vaporizer module using the fully concurrent evaporation technique. 相似文献
979.
《Arabian Journal of Chemistry》2022,15(1):103507
Syzygium brachythyrsum is an important folk medicinal and edible plant in Yunnan ethnic minority community of China, however, little is known about the chemical and bio-active properties. The present study is aimed to identify the bioactive constituents with antioxidant and anti-inflammatory properties by an integrating approach. First, two new bergenin derivatives, brachythol A (1) and brachythol B (2), together with eleven known phenolic compounds (3–13) were isolated from bioactive fractions by phytochemical method. Among these isolated chemicals, five bergenin derivatives, along with 3 phenolics were found in Syzygium genus for the first time. Then, a further chemical investigation based on ultra-high-performance liquid chromatography-Q Exactive Orbitrap mass spectrometry resulted in a total of 107 compounds characterized in the bio-active fractions, including 50 bergenin derivatives, among which 14 bergenin derivatives and 14 phenolics were potential new natural chemicals. Most of the isolated compounds showed obvious antioxidant activities, while compounds 11, 12, and 13 had favorable performance. Eight compounds (2–5, 7, and 9–11) showed good inhibitory activity on nitric oxide (NO) production in macrophage RAW 264.7 cells. The structure–activity correlation analysis indicated that the antioxidation and anti-inflammatory activities enhanced when bergenin was esterified with gallic acid, caffeic acid or ferulic acid. This is the first report of bergenins in Syzygium genus and the richness in new bio-active bergenins and gallic acid derivatives indicated that Syzygium brachythyrsum is a promising functional and medicinal resource. 相似文献
980.
Montoudis A Boileau S Simoneau L Mounier C Lafond J 《Biomedical chromatography : BMC》2004,18(9):706-713
Alternative HPLC and solid-phase extraction column methods were developed to separate metabolites of enzymes involved in cholesterol metabolism in rabbit liver microsomes: hydroxyl-methylglutaryl-CoA reductase, cholesterol-7alpha-hydroxylase and acyl-CoA:cholesterol acyltransferase. A comparison method of thin-layer chromatography and solid-phase extraction column were assayed to separate substrate and metabolite of hydroxy-methylglutaryl-CoA reductase, whereas for cholesterol-7alpha-hydroxylase and acyl-CoA:cholesterol acyltransferase, this comparison was done between thin layer chromatography and HPLC. The results obtained by the new analytical chromatographic methods are not significantly different than those observed in literature. Moreover a larger percentage recovery was obtained for analysed metabolites. Our results demonstrate the reliability of these alternative chromatographic techniques and showed that they are valuable tools to precisely and rapidly measure the activity of those enzymes. 相似文献