Chromatography flow programming

The gases used were purchased premixed in aluminum cylinders to avoid carbonyl formation. The high purity gas mixture was further purified by a zeolite water trap and a copper carbonyl trap. The gas pressure in the reactor was measured with a capci-tance manometer and the fTow monitored with a mass fTow controT-ler. The typical gas flow rates were 15 cc/min (STP) and the maximum conversion was 1% based on integration of hydrocarbon products. The hydrocarbon products were analyzed by gas chromatography (temperature programmed chromosorb 102, FID). 

Flame ionization detector (FID), 126-129 Flash chromatography, 222, 280 Fast LC, 200 Flow, measurement of, 63 Flow programming, 8, 150 Flow resistance parameter, 64 Fluorescence detector, 207-208 Frontal analysis, 6... 

Flow programming is not as effective in reducing the elution time of well-retained components and tends to cause increased band dispersion it is, however, more gentle than temperature programming and would be chosen when separating thermally labile materials. The complexity of the theoretical treatment depends on whether the mobile phase is compressible or not. In gas chromatography, the mobile phase is compressible, and this must be taken into account in the first theoretical treatment. 

Flow programming offers advantages such as reduced separation lime, less column bleed, and lower eluting temperature for labile compounds but has not been widely used in gas chromatography because temperature programming is experimentally easier to perform. In 1990, electronic pressure control (EPC) [30J was developed, which allows operation in the constant-pressure, constant-flow, and pressure-programming modes. Whether temperature programming will be re-... 

Oka, K, Dobashi, Y, Ohkuma, T, and Hara, S. (1981) Liquid column switching extraction and chromatography for programmed flow preparation J, Chromatography 217, 387-398... 

Gas chromatography on a 200 cm. by 0.6 cm. column packed with 10% Apiezon L on Chromosorb W (AW, DMCS) using a flame-detector instrument, at a 40 ml./minute helium carrier gas flow rate, gives a trace peak at 9.9 minutes (diphenylmethane), a major peak at 11.7 minutes (1,1-diphenylethane), and a trace peak at 15.4 minutes (1.1-diphenylethanol) when the oven is held at 190° for 10 minutes and then programmed at 10°/minute to 290°. 

Gel Permeation Chromatography. The instrument used for GPC analysis was a Waters Associates Model ALC - 201 gel permeation chromatograph equipped with a R401 differential refractometer. For population density determination, polystyrene powder was dissolved in tetrahydrofuran (THF), 75 mg of polystyrene to SO ml THF. Three y -styragel columns of 10, 10, 10 A were used. Effluent flow rate was set at 2.2 ml/min. Total cumulative molar concentration and population density distribution of polymeric species were obtained from the observed chromatogram using the computer program developed by Timm and Rachow (16). 

The separation nuaber is the only column efficiency par2uaeter that can be deterained under teaperature progr2uued conditions [45,46]. The critical parameters that aust be standardized to obtain reproducible SM values for coluans of different length are the carrier gas flow rate and the temperature program. The SN is widely used as part of a standardized test method to evaluate the quality of open tubular columns for gas chromatography (section 2.4.3). 

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