68 468
Assignments Done
98,6%
Successfully Done
In December 2018

Answer to Question #39058 in Physical Chemistry for edward ton

Question #39058
dear sir
I HAVE A QUESTION ABOUT GAS CHROMATOGRAPHY.WHEN WE USE CONSTANT PRESSURE OR CONSTANT FLOW FOR COLUMN OR IN MAKE METHOD FOR ANALYSIS?
BEST REGARDS
TONE
Expert's answer
If you're doing a relatively minor temperature program (say from 50C to 150C), then you won't notice much difference between constant flow and constant pressure modes. If you're doing a more "dramatic" temperature program (say from 35C to 350C), then the differences will be significant due to the relatively large reduction in column flow as you reach higher oven temperatures. Personally, I've just become used to using constant flow mode and that's what I normally default to when doing method development now.
With a more "dramatic" temperature program (larger temperature range), then you will see a reduction in retention time for late eluting compounds in constant flow mode. Additionally, you may see an improvement in resolution for late eluters in const flow mode as well, depending upon initial conditions. This is because there can be very significant changes in carrier gas linear velocity in constant pressure mode for temp programs with a large temperature range.

Need a fast expert's response?

Submit order

and get a quick answer at the best price

for any assignment or question with DETAILED EXPLANATIONS!

Comments

No comments. Be first!

Leave a comment

Ask Your question

Submit
Privacy policy Terms and Conditions