Temperature Programming for High-Speed GC

Abstract

Fast temperature programming (20-50 °C/min) is used with relatively short separation columns to achieve high-speed separations of mixtures covering a wide boiling point range. A cryofocusing inlet is used to obtain narrow injection plugs. High-speed temperature-programmed chromatograms are evaluated by considering local peak capacity as a function of carbon number and boiling point for the normal alkanes in the range C(8)-C(19). The peak capacity generation rate (peaks per second) as a function of carbon number and the total cumulative peak capacity as a function of time are also considered for various column lengths and carrier gas flow rates. Column lengths in the range 3.6-25.4 m and average carrier gas velocity values in the range 50-200 cm/s are considered. For a 6.8-m-long, 0.25-mm-i.d. column operated at an average carrier gas velocity of about 100 cm/s and using a nominal programming rate of 50 °C/min, C(19) elutes in 178 s with a total peak capacity of 168 peaks. If the programming rate is reduced to 20 °C/min, the C(19) elution time more than doubles but the total peak capacity increases by only 20%. For a 25.4-m-long column using a nominal 50 °C/min programming rate, the C(19) retention time is 262 s with a peak capacity of 279 peaks. The use of average carrier gas flow rates greater than about 100 cm/s, which is common in isothermal high-speed GC, results in a considerable loss in total peak capacity with remarkably little reduction in analysis time.

How Cells Respond to Interferons

“…The adenovirus E1A and human papilloma virus E6 and E7 proteins inhibit the production and action of IFN at the level of transcription (66,(191)(192)(193)(194). For E1A, the effect on the transcription of ISGs is mediated, in part at least, through a reduction in functional p48 (192,193) and probably also by sequestering p300/CBP, required for transcriptional activation through STAT2 (82).…”

“…For E1A, the effect on the transcription of ISGs is mediated, in part at least, through a reduction in functional p48 (192,193) and probably also by sequestering p300/CBP, required for transcriptional activation through STAT2 (82). A similar inhibition at a transcriptional level of IFN production and action is mediated by the Kaposi's sarcoma herpes virus through the production of an inhibitory mimic of IRF (169).…”

Evaluation of split/splitless operation and rapid heating of a multi-bed sorption trap used for gas chromatography analysis of large-volume air samples

“…These values were chosen to give a temperature change of about 208C during an interval equal to the column holdup time. Previous studies have shown that larger temperature changes result in substantial losses in resolution [29,30]. To prevent loss of resolution for the early-eluting components, isothermal operation at 308C was used for 120 s for (a) and (b), 60 s for (c) and (d), and 30 s for (e) and (f).…”

Hadamard‐Transformations‐Flugzeitmassenspektrometrie: gesteigerte Signalintensität bei gleicher Messzeit

“…Diese Tatsache begrenzt die Spektrenaufnahmegeschwindigkeit des Massenspektrometers. Werden die Signalbreiten der eluierten Verbindungen schmaler ± wie bei Mikrochiptrennungen, [15] bei schnellen gaschromatographischen Trennungen [16] oder bei der ultraschnellen Kapillarelektrophorese [17] ± kann der massensensitive Detektor unter Umst‰nden mit der Trenngeschwindigkeit nicht Schritt halten. Man erh‰lt dann drastisch verzerrte Signale.…”