Gas chromatography

[nacho]

Question:
What is the purpose of the oven which heats the column?
It is my understanding that the substance under analysis is already vapourised prior to entering the column? OR am i mistaken?

[Water]

I"m pretty sure, the purpose of the oven which heats the column is so that the sample remains as gas throughout the entire process.

[luken93]

I"m pretty sure, the purpose of the oven which heats the column is so that the sample remains as gas throughout the entire process.

Yeah, it's vaporised at the injection port

[nacho]

Also, i was wondering why it is that water can be used as a mobile phase in PC?
Wouldn't the cellulose form hydrogen bonds with the water, and then the water would also become a stationary phase?

Could someone also list factors that affect the of a substance?
(e.g size - i think... seems like a dodgy example though)

[Dr.Lecter]

adsorption

[luken93]

Also, i was wondering why it is that water can be used as a mobile phase in PC?
Wouldn't the cellulose form hydrogen bonds with the water, and then the water would also become a stationary phase?

You can use water for the splitting of polar compounds, as they will all somewhat bond to the water to be carried, but I've never heard about cellulose?

Could someone also list factors that affect the of a substance?
(e.g size - i think... seems like a dodgy example though)

- Size, as heavier substances will be slower to move
 - Temperature, as it will move faster if it is heated
 - Pressure, the higher the pressure the more it will be pushed through.

[nacho]

You can use water for the splitting of polar compounds, as they will all somewhat bond to the water to be carried, but I've never heard about cellulose?

Thanks

Paper is made of cellulose, and cellulose is polar.
Does this mean that the mobile phase will also adsorb to the cellulose is what i am wondering.

Just another follow up question,
the size of the substance would not be as relevant Cf the intramolecular forces at play are, would it?
For example, a larger component of a substance, that is polar will have a higher than a different small component of the substance which is non-polar, correct? (assuming our solvent/M.P is also polar)
But in the case where the same large component is tested twice, once where it is of low concentration and one where it is of high concentration, will the lower concentrated sample move slower?
I thought that since it was large, it would have more polar areas on it to desorb to the water, and thus a larger concentrated component would move faster.

[luken93]

You can use water for the splitting of polar compounds, as they will all somewhat bond to the water to be carried, but I've never heard about cellulose?

Thanks

Paper is made of cellulose, and cellulose is polar.
Does this mean that the mobile phase will also adsorb to the cellulose is what i am wondering.

Hmmm I don't know, I've never really seen anything of the sort in textbooks...
Even if it did, does it matter afterall, as it's still going to affect everything in the same way?