State of the compound at initial oven temperature

[kalidassa]

Hai every one

I have one doubt can any one please clarify me. We are injecting the compounde in higher temperature (minimum 100°C to 150°C) when this compounts entering in to the column at initial oven temperatue which very low than the injection temperatue ( 40°C, 50°C or 60°C). What may be the actual state(phase) of the compound in our column while travelling at this lower oven temperature. Because we are suddenly changing the temperature oto lower.

Thank you
KALIDASS

[Peter Apps]

Any compound travelling through a GLC column is in two states: as a vapour mixed with carrier gas, and as a solution on the stationary phase.

Peter

[kalidassa]

Thank you for answering. Can you please explain well is there any mechanism is there for that.

Thank you
KALIDASS

[Jumpshooter]

Kali: when your analyte is first injected at the 150C it is likely transformed from a liquid state (dissolved in organic solvent) into a gaseous state, then when your oven is set at 50C the compound condenses back to a "liquified" state where it becomes "dissolved" into the column's liquified stationary phase. It "sits" there until the input of energy (heat) is sufficient to make it "boil off" the stationary phase and disperse into the carrier gas (mobile phase). Then swept into the detector.
There are complex mathematical formulae that describe this process in terms of partitioning coefficients, free energy, heats of vaporization, and the like---but suffice it to say that your compound remains tucked in the stationary phase until there is sufficient energy input that causes it to "wiggle" free and partition itself into the gas phase.

[Peter Apps]

Try googling Gas Chromatography mechanism, or search the forum archives.

Peter

[DR]

While you're at it, google "cold trapping"