Specific retention volumes, retention indices, and family‐plot regressions of aliphatic, alicyclic, and aromatic hydrocarbon solutes with OV‐101 poly (dimethylsiloxane) stationary phase
“…Those eluting between the n 1-alkene and the n cis-2-alkene were labeled "alkenes" (i.e., straight chain). The assignment of carbon number and identity was based on elution orders represented by the retention indices tabulated for nonpolar columns by White et al (1992) and Laub and Purnell (1988).…”
C 1 -C 30 products from Fischer-Tropsch synthesis, conducted in a supercritical n-hexane medium over an Fe catalyst in a fixed-bed reactor, are analyzed using on-line gas chromatography. A Hewlett-Packard 5890 Series II gas chromatograph (GC) is modified to minimize the effects of condensation of the on-line sample in the transfer lines. The GC is configured with a Supelco Petrocol DH capillary column connected to a flame ionization detector (FID) and two 1.83 m × 3.18 mm stainless steel columns placed in series, packed with 80/100 mesh HayeSep D, connected to a thermal conductivity detector (TCD). It is shown that pressure and temperature affect the elution order of oxygenates relative to hydrocarbons in the nonpolar capillary column. This phenomenon is exploited for obtaining improved resolution; several distinct methods produce similar elution orders. Ar, added to the syngas feed, is used to calculate syngas conversion. All compounds eluting before hexane (C 1 -C 5 , other than 2-methylpropene/1-butene and propanal/ propanone) and nearly all the major peaks eluting after hexane are resolved in the capillary column. H 2 , Ar, CO, CH 4 , CO 2 , and H 2 O are resolved in the packed columns. The method provides excellent quantitative measurement of component mole fractions that are within the range of calibration.
“…Those eluting between the n 1-alkene and the n cis-2-alkene were labeled "alkenes" (i.e., straight chain). The assignment of carbon number and identity was based on elution orders represented by the retention indices tabulated for nonpolar columns by White et al (1992) and Laub and Purnell (1988).…”
C 1 -C 30 products from Fischer-Tropsch synthesis, conducted in a supercritical n-hexane medium over an Fe catalyst in a fixed-bed reactor, are analyzed using on-line gas chromatography. A Hewlett-Packard 5890 Series II gas chromatograph (GC) is modified to minimize the effects of condensation of the on-line sample in the transfer lines. The GC is configured with a Supelco Petrocol DH capillary column connected to a flame ionization detector (FID) and two 1.83 m × 3.18 mm stainless steel columns placed in series, packed with 80/100 mesh HayeSep D, connected to a thermal conductivity detector (TCD). It is shown that pressure and temperature affect the elution order of oxygenates relative to hydrocarbons in the nonpolar capillary column. This phenomenon is exploited for obtaining improved resolution; several distinct methods produce similar elution orders. Ar, added to the syngas feed, is used to calculate syngas conversion. All compounds eluting before hexane (C 1 -C 5 , other than 2-methylpropene/1-butene and propanal/ propanone) and nearly all the major peaks eluting after hexane are resolved in the capillary column. H 2 , Ar, CO, CH 4 , CO 2 , and H 2 O are resolved in the packed columns. The method provides excellent quantitative measurement of component mole fractions that are within the range of calibration.
“…2a), but there are some differences between both chromatograms. On the TIC chromatogram there seems to (2001); (2) Hayes and Pitzer (1985); (3) prediction using the method of Zenkevich (1998); (4) HaagenSmit Laboratory (1997); (5) Laub and Purmell (1988); (6) Lubeck and Sutton (1984); (7) Helmig et al (1996); (8) Bermejo et al (1987); (9) Andrade et al (2000); (10) (2000); (15) Madruga and Mottram (1998); (16) Weber (1986) be a band 0.4 s above the lowermost band (i.e. the alkane band).…”
Abstract.During the MINOS campaign in August 2001 comprehensive two-dimensional gas chromatography (GC×GC) was applied to the in situ measurements of atmospheric volatile organic compounds (VOCs) at the Finokalia ground station, Crete. The measurement system employs a thermal desorption unit for on-line sampling and injection, and a GC×GC separation system equipped with a flame ionization detector (FID) for detection. The system was optimized to resolve C 7 − C 14 organic components. Two-dimensional chromatograms from measurements of Finokalia air samples show several hundred wellseparated peaks. To facilitate peak identification, cartridge samples collected at Finokalia were analyzed using the same GC×GC system coupled with a time-of-flight mass spectrometer (TOF-MS). The resulting mass spectra were deconvoluted and compared to spectra from a database for tentative peak identification. About 650 peaks have been identified in the two-dimensional plane, with significant signal/noise ratios (>100) and high spectra similarities (>800). By comparing observed retention indices with those found in the literature, 235 of the identifications have been confirmed. 150 of the confirmed compounds show up in the C 7 − C 14 range of the chromatogram from the in situ measurement. However, at least as many peaks remain unidentified. For quantification of the GC×GC measurements, peak volumes of measured compounds have been integrated and externally calibrated using a standard gas mixture.
“…In this report, we show that, in a constant-pressure mode, the combined effect of the temperature dependences in t M and θ char is a reduction in the spread of R T,opt . Particularly, for over 180 solutes (12 n -alkanes and 12 pesticides from our experiments and over 150 solutes from the literature , ) examined a our previous study 1 , the correlation between t M and θ char reduces a relative standard deviation of distribution of R T,opt by a factor of ∼2.…”
mentioning
confidence: 74%
“…Equation 5 also suggests a simple way of finding of R T,opt for a single-ramp temperature program with a given r opt . 1 Characteristic thermal constants, θ char , of light hydrocarbons, n -alkanes, pesticides, and miscellaneous solutes 6 versus their characteristic elution temperature, T char . A line represents the least-squares fit of the function eq 4.…”
mentioning
confidence: 99%
“…Characteristic thermal constants, θ char , of light hydrocarbons, n -alkanes, pesticides, and miscellaneous solutes 6 versus their characteristic elution temperature, T char . A line represents the least-squares fit of the function eq 4.…”
In a temperature-programmed analysis, the solutes that elute at higher temperatures have generally larger characterisitic thermal constants, theta(char). The change approximately matches the temperature-related increase in a carrier gas viscosity. Accounting for the effect allows reduction in the uncertainty of prediction of theta(char) by a factor or f approximately 2 and, in a constant-pressure mode, description of a linear heating ramp by the same dimensionless rate for all solutes.
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