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161.
The introduction of selected fractions from a liquid chromatograph into a gas chromatograph has been described; however, analyses were performed by off-line experiments requiring collection and reinjection of the separate fractions or by on-line procedures where disadvantageously, only a fraction of the separated peak or a well resolved component in a mixture could be introduced into a gas chromatograph. This disadvantage is overcome by the apparatus and method described in this paper, which utilizes a multidimensional chromatography system employing a high efficiency, packed capillary LC column coupled on-line to a capillary gas chromatograph. The liquid chromatograph (so designed) can act as a highly efficient clean-up or chemical class fractionation step prior to introduction into the gas chromatograph, significantly reducing sample preparation times in many applications. Thus minor components in a complex matrix can be determined without prior sample clean-up, an example of which is the determination of polychlorinated biphenyls in a complex hydrocarbon matrix. 相似文献
162.
Summary Separation and determination ofFusarium trichothecenes: nivalenol, deoxynivalenol, fusarenone and 3-acetyldeoxynivalenol, were carried out by highperformance liquid chromatography with UV detection, and methanol—water (30/70) as mobile-phase on Lichrosorb RP-18 column. Detection limits were 2, 3, 3 and 5ng per injection of nivalenol, deoxynivalenol, fusarenone and 3-acetyldeoxynivalenol, respectively. The method appears to be adequate for detection of the above trichothecenes in contaminated corn and rice as well as in cultures ofFusarium spp. A preliminary TLC purification was necessary for detection of fusarenone in corn. 相似文献
163.
In this paper the equation for thin-layer adsorption chromatography with multicomponent mobile phases, proposed by O?cik in 1965 is extended to energetically heterogeneous solid surfaces. Other forms of this equation, more convenient in practical applications, are presented. Model calculations are made for TLC with binary mobile phases according to the modified form of O?cik's equation. Finally, this equation is compared with that of Snyder. 相似文献
164.
165.
M. R. Gregg 《Chromatographia》1985,20(2):129-133
Summary Electrode surface modification by electrochemical pretreatment of glassy carbon electrodes was shown to enhance significantly the sensitivity of the electrodes for the detection of timolol and oxprenolol, but reduce slightly the sensitivity to prenalterol. This method may permit the detection of exprenolol and timolol with increased sensitivity, or may allow their detection at lower applied potentials than is presently possible. Electrode surface modification may prove to be a valuable aid to the detection of compounds that are considered to be outside the practical limits of electrochemical detection. 相似文献
166.
Umaporn?Paiphansiri Pramuan?TangboriboonratEmail author 《Colloid and polymer science》2005,284(3):251-257
The prevulcanisation of skim latex, a by-product of field natural rubber (NR) latex concentrated by centrifugation, using sulphur and peroxide systems was investigated. Compared to the peroxide prevulcanisation, the lower swelling ratio of film casted from sulphur-prevulcanised skim (SPVS) latex was observed. The latter was then employed for preparation of NR/SPVS core–shell particles by using heterocoagulation technique whose driving force was an interpolymer complex between poly(ethylene oxide) (PEO) moieties of a non-ionic surfactant (Nonidet) adsorbed on small SPVS particles and the indigenous surfactant (protein–lipid) on a large NR particle. The value of zeta potential of heterocoagulated particle and the better oil resistance of films casted from the composite latex when compared to that of the NR film revealed the NR/SPVS core–shell structure. 相似文献
167.
The phase transitions of a new group of mesogens, 2-(4-alkoxyphenyl)-6-substituted benzothiazoles were thermodynamically studied by DSC, and their transition temperatures and enthalpy changes were measured, from which the transition entropy changes were calculated. The results obtained were discussed. In addition, the phe-nomenon of super-cooling of the compounds were quantitatively observed. 相似文献
168.
A mathematical method for the calculation of the dead time (tm) in HPLC was evaluated using a computer simulation approach, in which artificial perturbations were introduced to Simulated homolog retention times. The calculation was based on a modified and extended Grobler and Bálisz (GB) method. Investigated wav how the precision of the calculated tM is affected by: statistical fluctuations in retention times and which, and how many homolog retention times are used. Based on these simulations a two-step procedure for the tM calculation is proposed: In the first step the linearity of log tR, n vs carbon number n is checked using as many homolog retention times as possible. The slope value bo of the first linear regression in the GB method is used for the selection of homolog retention times in the final tM calculation. In the second step the optimal selection of homologs is made and the final tM calculation is carried out. Guidelines for homolog selection are given. 相似文献
169.
Effect of pressure on oxygen enrichment of liquid crystalline cellulose ether membranes at elevated temperature 总被引:1,自引:0,他引:1
Cholesteric liquid crystalline triheptyl cellulose (THC)/ethyl cellulose binary blend membranes were prepared and the effect of pressure on their oxygen enrichment at elevated temperature was investigated using a constant pressure-variable volume method. The oxygen enrichment increased with the increase of transmembrane pressure difference or with slight increase of the THC content in the blend membranes. The oxygen concentration through the membranes increased linearly with decreasing pressure ratio. Air was directly separated through a 17 m-thick THC/EC(1.5/98.5) membrane to prepare an oxygen-enriched air containing 39.5% oxygen at the flux of 6.99×10–4 cm3 (STP)/s.cm2 at the pressure difference of 0.43 MPa and 85 °C. 相似文献
170.
Bixing Fang Lina Dong Xingwei Ding YingZi Ren Zhongsheng Lv Kuan Liu Feng Zhang Wei Zhang Jianjian Deng Hongbo Xin Xiaolei Wang 《中国化学快报》2019,30(6):1178-1181
Black fungus aerogel (BFA) exhibited interesting double-faced properties. Weexplored the diverse properties of each side of the black fungus in three aspects:water contact angle measurements, liquid selective absorption capacity and air pollutant adsorption abilities. 相似文献