Chromatography Forum

Greetings,
I noticed that acetone solvent is not eluted within 4 min. I had no such problem at all before I attached a guard column to my HP-5ms column. The guard column is 0.53mm ID, internetiate Polarity fused silica SUPELCO guard column.

codition of my experiment is:
splitless, purge time 1min with 50mL/min purge, 900uL liner, 47-230 C, 20 C/min, 1ml column flow, it almost took 10min for acetone's abundance to drop down below 40000.

if with split 100:1 mode, it also took about 9 min before I can have a flat baseline.

Please help!

Hi Ziman

How is your guard column connected to the analytical column ?

Peter

If your HP column is also 0.53mm, your flow could be higher. It's taking ~1min (or more depending on how long the ret. gap is) for anything to get to the column.

Thanks for your reply.
I used metal connector with double tapered graphite ferrule to connect guard column and HP column.
my HP column is 0.25mm ID.

I had this problem with acetone. but if I switched to 2-propanol, my base line was flat right after solvent delay (4 min). For acetone, after solvent delay, base line started at a fairly high abundance 1e5, then dropped to about 20000 after 10 min. I thought maybe the stationary phase in the guard column was soluble in acetone?

thanks.
ziman

Hi Ziman

Use a press-fit connector instead of a compression union - the acetone is absording - desorbing on the graphite ferrule.

When you change connectors cut about 50 cm off the beginning of the analytical column and 5 cm off the end of the retention gap, because it is very likely that you have introduced particles of graphite into the columns.

Peter

Thank you so much Peter, I am going to try press-fit connector.

Hi Peter,
you are great. I tried a press-fit connector and that huge solvent delay was gone. Thanks a lot!

ziman