Seperation of gasses and early eluting compounds

[JonKlar]

Hey guys, Im having a problem seperating the peaks that elute before my temp program kicks in. I am testing for VOCs under EPA method 624 and the compounds giving me trouble are vinyl chloride, chloroethane, ethanol, bromomethane, and a few others.

I am using a 7890A
HP-5MS column .25um by 30mm
Constant flow rate of 1.2 ml/min
Front inlet temp 230C
1:20 Split
holding 35C for 4 minutes


I was previously running a 1:100 split and constant pressure of 19(mmtorr i think?) which had my flow rate up to 2.4, but was also giving me better seperation.

Any insight would be appreciated, thanks!

[LindseyPyron]

If you download the app note below and use the GC conditions and column listed, you should be good to go....

http://www.estanalytical.com/presentati ... 20Note.pdf

[JonKlar]

Funny, I just changed to the column (20x.18) described in that article last night. I will try these parameters today, thanks!

Jon

[chromatographer1]

Jon

You are running at twice optimum flow at 1.2 mL per minute.

You need plates. Set your flows at near optimum for more plates, or go to a smaller id COLUMN.

best wishes,

Rod

[JonKlar]

The new column is working great. Best calcurve ive had in a long time, thanks for all of your guys help! The parameters given were spot on and the flow was definitely too high.


Jon