Question about azeotropes(sp?)(and a little side GC question)

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Thearchitect

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If I have an azeotrope(let's say a 50/50 mixutre), it's impossible by fractional distillation to get a pure compound of the lower boiling point one? Because it at some point it will start to boil at a set ratio and stay that way until the lower BP one is gone then it will just be 100% the higher bp one, right?

Also, does anyone know how to obtain the retention time from a gas chromotograohy read out, with the chart speed being set at 2cm/min. I have the chart and the areas of the peaks, but I don't know what I'm supposed to do to get the retention time.
 
Thearchitect said:
If I have an azeotrope(let's say a 50/50 mixutre), it's impossible by fractional distillation to get a pure compound of the lower boiling point one? Because it at some point it will start to boil at a set ratio and stay that way until the lower BP one is gone then it will just be 100% the higher bp one, right?

Also, does anyone know how to obtain the retention time from a gas chromotograohy read out, with the chart speed being set at 2cm/min. I have the chart and the areas of the peaks, but I don't know what I'm supposed to do to get the retention time.


For retention time, find the distance from the beginning of the graph to the peak. If the distance is 5 cm, the retention time will be 2.5 min (cause ur rate was 2cm/min). However, make sure that you are calculating retention time, and not adjusted retention time for which you find the distance between air peak (or mobile phase peak) and your compound.

I don't quite understand your azeotrope question. Can you put in a better way? Sorry.
 
Thearchitect said:
If I have an azeotrope(let's say a 50/50 mixutre), it's impossible by fractional distillation to get a pure compound of the lower boiling point one? Because it at some point it will start to boil at a set ratio and stay that way until the lower BP one is gone then it will just be 100% the higher bp one, right?

Yes, that's correct.
 
Thanks guys. If that's how I find the retention factor, though, I wonder why we are suppose to record the areas of the peaks. hmm.
 
The areas of the peaks tell you the amount of your compound. Bigger area = more amount of that compound
 
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