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101.
J. L. Daft 《Journal of separation science》1983,6(9):480-487
Residue mixtures of pesticides in foods which were difficult to separate by packed-column gas chromatography were determined by capillary gas chromatography and electron capture detection. Manual injections of sample and reference standard were made with a 10 μL syringe on a septum-enclosed, split/ splitless inlet system. Optimal peak height repeatability (± 3%( was achieved with three-μL injections which were made within time periods of four hours or less. The average linearity coefficient (slope( obtained for detector response as a function of solution concentration was 1.1. 相似文献
102.
Summary A micro carbon rod atomizer has been employed for specific and quantitative bromine determinations. This Br-specific gas-chromatographic detector works by help of InBr-bands and measurement at 372.7 nm. The performance of this flame band emission detector (FBD) is demonstrated by calibration curves and the detection limits of 2 examples (ethyl bromide, ethylene dibromide), the latter being 5 and 36 ng of bromine, respectively. The reproducibility has been found to be 4.3%. An example of this detector in comparison with a thermoconductivity detector (TCD) is presented.
Verwendung einer Mikro-Graphitküvette als Br-spezifischer Detektor für die Gas-Chromatographie
Zusammenfassung Eine Mikro-Graphit-Küvette wird für spezifische quantitative Brombestimmungen nach der Indium-Methode bei 372,7 nm benützt und in Verbindung mit einem Gas-Chromatographen als Br-spezifischer Detektor eingesetzt. Die Leistungsfähigkeit dieses Detektors wird an 2 Beispielen (Äthylbromid, Dibromäthan) mit Hilfe von Eichkurven, Bestimmung von Nachweisgrenzen u. ä. demonstriert. Die Nachweisgrenzen liegen bei 5 bzw. 36 ng Brom für die 2 genannten Substanzen. Die Reproduzierbarkeit der Messungen liegt bei 4,3%. Ein Beispiel für die Registrierung eines Gemisches verschiedener Substanzen, gemessen mit dem GC + Flammen-Banden-emissions-Detektor (FBD) und zum Vergleich mit einem Wärmeleitfähigkeitsdetektor (TCD), wird dargestellt.
This research work was supported by financial help of the Bundesminister für Forschung und Technologie in Bonn (GFR). 相似文献
103.
K. Grob 《Journal of separation science》1980,3(6):286-290
The sensitivity of an FID may change when the carrier gas flow rate changes during a chromatographic run. Sample parts which are eluted at reduced FID sensitivity produce a reduced peak area, hence are discriminated as compared to other components. Sensitivity changes were studied for hydrogen as carrier gas. For the detector tested, differences in the carrier gas flow rates of 1 ml/min shifted the FID sensitivity by 1 to 5% (depending on the fuel gas supply). Thus the stability of the sensitivity is no longer ensured as soon as the carrier gas flow rate is changed manually or by an automatic programmer during an analysis. Sensitivity drifts may also occur during temperature programmed runs with a pressure regulated carrier gas supply since the gas flow through the capillary drops with increasing temperature. Such shifts in the response became noticeable as soon as relatively high carrier gas flow rates combined with long range temperature programmes were used. The typical patterns of such discriminations are shown, closing with a discussion on the possibilities for minimizing such undesired effects. 相似文献
104.
Norikazu Nishiyama Yong-Rong Dong Tao Zheng Yasuyuki Egashira Korekazu Ueyama 《Journal of membrane science》2006,280(1-2):603-609
Microporous carbon membranes were prepared on an -alumina support by a pyrolysis of cationic tertiary amine/anionic polymer composites. The precursor solutions contain a thermosetting resorcinol/formaldehyde (RF) polymer and a cationic tertiary amine. Three types of cationic tertiary amines with different chain lengths were used, such as tetramethlammonium bromide (TMAB), tetrapropylammonium bromide (TPAB) and cetyltrimethylammonium bromide (CTAB). A porous structure was produced by a decomposition of the amine and the resulting pores assisted the further gasification of the RF polymer at high temperature. The carbon/alumina membranes have thin and continuous carbon top layers with a thickness of 1 μm. Gas permeation tests were performed using single gases of CO2, O2, N2, CF4, n-C4H10 and i-C4H10, as well as binary mixtures of CH4/n-C4H10 and N2/CF4 at different temperatures between 23 and 150 °C. The carbon membrane prepared using TMAB showed separation factors higher than 650 for the CH4/n-C4H10 mixtures and higher than 8100 for the N2/CF4 mixture. From the permeation of pure gases with different molecular sizes, the pore sizes of the carbon membrane prepared using TMAB, TPAB and CTAB are estimated to be 4.0, 5.0 and larger than 5.5 Å, respectively, indicating that the micropore size of the carbon membranes is controllable by using different amines. 相似文献
105.
《中国化学快报》2020,31(4):922-930
MXenes have emerged as versatile 2D materials that are already gaining paramount attention in the areas of energy,catalyst,electromagnetic shielding,and sensors.The unique surface chemistry,graphene-like mo rphology,high hydrophilicity,metal-like conductivity with redox capability identifies MXenes,as an ideal material for surface-related applications.This short review summarizes the most recent reports that discuss the potential application of MXenes and their hybrids as a transducer material for advanced sensors.Based on the nature of transducing signals,the discussion is categorized into three sections,which include electrochemical(bio) sensors,gas sensors,and finally,electro-chemiluminescence fluorescent sensors.The review provides a concise summary of all the analytical merits obtained subsequent to the use of MXenes,followed by endeavors that have been made to accentuate the future perspective of MXenes in sensor devices. 相似文献
106.
Summary A method is described for the determination of small quantities of hydrochloric acid in two chlorinated organic solvents (CHCl3 and CCl4). An excess of gaseous ethylene oxide is added to a liquid sample; the 2-chloroethanol formed is then analyzed by gas chromatography. The procedure is simpler and more sensitive in comparison with other conventional methods. It can be modified for other organic solvents.D.G.R.C.S.T. grant. 相似文献
107.
Surface modification of soft-glass capillaries for gas chromatography by treatment with water vapour
“Leaching” or “etching” by strong mineral acids seems to be a necessary pretreatment step for the most commonly used deactivation procedures of glass capillaries by reaction with either polyethylene glycol or silylation reagents. The acidic sites which are formed on the surface during this acid treatment cannot be completely removed by the subsequent deactivation process. This drawback can be overcome by performing the leaching with water vapour, resulting in an accumulation of cations at the surface and a decrease in the number of silanol groups. Capillaries of this type show excellent properties for the chromatography of strongly basic compounds. After the wash-out of the alkaline surface layer, the acidity of the support is suited for the chromatography of strongly basic as well as strongly acidic compounds. Due to a lack of reactive acidic sites, special deactivation procedures have to be applied to capillaries produced in this way. 相似文献
108.
109.
Summary The esterification of C1–C8 fatty acid in aqueous solutions and in the presence of sulfuric or hydrochloric acid and with n-butanol is described. It has been established that the esterification can be used for the quantitative determination of these fatty acids in the concentration ratio range of [H2O]/[n-BuOH]=0.01–5.3. In the concentration ratio range of 0.01–0.8 the water present does not interfere. In the concentration range of above 0.8 anhydrous sodium sulfate is used for binding the water, in the amount of [Na2SO4.anh.]/[H2O]0.2. 相似文献
110.
Summary Diaromatics are geochemically significant constituents of crude oils. Their determination is usually achieved by elaborate prefractionation methods, such as medium pressure liquid chromatography and HPLC, prior to capillary gas chromatography. The present contribution describes the quantitative analysis of methylnaphthalenes, ethylnaphthalenes, and dimethylnaphthalenes in selected crude oils by two-dimensional capillary GC. Since the method does not comprise any work-up procedure the determination of geochemical parameters (alkylnaphthalene concentration ratios) is performed on the original, untreated crude oil samples. Accordingly, the analytical results reflect the original composition. The influence by evaporational losses in the laboratory is minimized. 相似文献