Chromatography Forum

I recently changed the column in my Agilent 5890 (split inlet with EPC and MS detector).
Now the max flow through the split vent I can get is only about 10 mL/min.
(I was able to get up to 100 mL/min plus with the previous column set up.)

I am wondering the best approach to trouble shoot this problem.

I don't seem to have an air leak since there is no evidence of that in the MS spectrum
so I assume the column is properly installed in the inlet.

The column I removed was a MolSieve, 30m, 0.32mm
The new column is a DB1, 40m, 0.18mm. I've set the head pressure to 25psi at 100deg C.

Any suggestions to approach this problem are appreciated.




setting total flows
for

Step 1, check that all the column dimension settings in the GC setup are correct for the new column.

Step 2. Measure the split and septum purge flows with an independent flow meter, not the on-board pneumatics, and measure the hold up time for an injection of an unretained substance (e.g. air).

Step 3. Check the gas saver settings in terms of time and flow rate.

Are you running with constant pressure, or constant flow, and if it is constant flow are you setting linear flow velocity or volume flow ?

For the split ratio; are you setting total flow or split ratio ?, what are the values of the settings ?

Peter

edfead,

Make sure you do not have an Aux EPC (C, D, E... etc...) that is your total flow controller upstream of your column EPC. I have seen this configuration before and if the Aux is not high enough you will never supply the column with enough flow to get what you want.

Best regards,

AICMM