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101.
102.
GC/MS法分析奶油中的脂肪酸 总被引:1,自引:0,他引:1
利用气相色谱/质谱/计算机联用技术分析人造奶油、天然奶油和新西兰奶油中的脂肪酸,从中鉴定出7种酸:棕榈酸、棕榈油酸、硬脂酸、油酸、亚油酸、亚麻油酸及花生酸。人造奶油含亚油酸比天然奶油含的高。 相似文献
103.
Summary Further to Gilpin's observations in liquid chromatography of the irreversible transformation of alkyl grafts, following the replacement of an organic mobile phase by an aqueous one, we describe some gas chromatographic experiments which lead to similar (log Vs, I/T) plots, as a consequence of the same solvent release process.We use paraffin films on siliceous supports or hydroxylated liquid substrates or C22-alkyl bonded silica. These experiments demonstrate that this irreversible transition and the melting-like reversible transition are completely different phenomena. They confirm the existence of at least three kinds of monomeric alkyl films. 相似文献
104.
Band broadening in capillary columns is satisfactorily described by the Golay-equation extended to situations of appreciable pressure drop by Giddings. In practice, however, several simplifications are often made. The effect of these simplifications on the calculated values of the minimum plate height and optimum carrier gas velocity are treated systematically. 相似文献
105.
106.
T. A. Gough 《Chromatographia》1979,12(4):195-196
Summary Several detectors which have a selective response toward nitrogen containing compounds are discussed. Data on sensitivities,
detection limits and reproducibility of response are given. The application of chemiluminescence to provide a nitrogen selective
GC detector is proposed. 相似文献
107.
Reported here is an analytical method enabling the stereochemical resolution of a new antianginal compound possessing two stereogenic centers, leading to four stereoisomers. Only one of these isomers is currently under development as a novel antianginal agent and consequently, the other three isomers are considered as unwanted chiral impurities. Therefore, an enantioselective method is required in order to check its enantiomeric purity. This paper presents a method exploiting the high efficiency of capillary electrophoresis and the complexing properties of cyclodextrins to achieve the separation of the four stereoisomers of this weakly basic compound (pKa = 7.4). For this purpose, the combination of a neutral cyclodextrin, hydroxypropyl-gamma-cyclodextrin (HP-gamma-CD), and an anionic cyclodextrin, carboxymethyl-beta-cyclodextrin (CM-beta-CD), was added to the separation buffer running in an uncoated silica capillary. After selection of the suitable cyclodextrin system, satisfactorily separation conditions were as follows: 30 mM phosphate buffer (pH 6.4) containing 10 mM of HP-gamma-CD and 10 mM of CM-beta-CD, running voltage +30 kV. The resulting run time and resolutions were respectively about 17 min and between 1.95 and 2.84. Linearity curves (0.993 < r2 < 0.998) are also shown. 相似文献
108.
109.
建立了高效毛细管电泳结合柱上紫外检测测定单胺类神经递质多巴胺(dopamine,DA)和5_羟色胺(5_hydroxytryptamine,5_HT)的毛细管电泳方法 ,优化了缓冲液 pH值、浓度、电压等实验参数 ;结果表明 ,在优化的实验条件下 ,多巴胺、3,4_二羟苄胺 (3,4_dihydroxybenzylamine)和5_羟色胺在10min内得到很好的分离 ,检出限分别为2.02×10 -5mol/L,1.01×10 -5mol/L,1.20×10 -5mol/L ;该法简便、快速 ,样品用量少 ,结果准确 ,重现性好 相似文献
110.
Yongsong Luo Xiaohong Xia Yonggang Zhang Jialin Li Zhijie Jia 《Journal of solid state chemistry》2007,180(6):1928-1933
Luminescence of the short multiwalled carbon nanotubes (MWNTs) conjugated with carboxylic acid groups has been studied. The results show that the carboxyl-functionalized short MWNTs could emit luminescence and the emission peak appears at 500 nm with a corresponding optimal excitation wavelength centering at 310 nm. When the short MWNTs are filtered through 0.15 μm polytetrafluoroethylene (PTFE) membrane, the ultrashort MWNTs are obtained from the filtrate. An interesting feature for the ultrashort MWNTs is that the emission intensity is strengthened and the peak is slightly blue shifted to 460 nm. This result indicates that the luminescence properties of MWNTs are strongly affected by the tube length. After chemical oxidization cutting, defects and carboxylic acid groups at the tube end and/or sidewall can be produced; the more shorten of MWNTs, the better dispersion and carboxylic passivation of the nanotubes, and the more intense luminescence emissions. The broad emissions are logically attributed to the trapping of excitation energy by defect sites in the carboxyl-functionalized nanotube structure. 相似文献