about baseline

[edmgc7788]

hi, i am using 7890a GCFID. The column is DB1, 15m length, 0.32mm ID,0.15um .I also use temperature programme, start 40 to 360.
My question is my back column, after solvent elute, at the end of peak, it's not right angle, seem like tailing. Does it cause by liner?
thank you
rebecca chen

[Peter Apps]

Solvent peaks always tail somewhat. As long as the peaks that you are interested in are not affected, the solvent tail is not a problem. The most common cause of solvent peak tails is dirt in the inlet.

Peter

[uzman]

To decrease the solvent peak tailing , you may increase the headpressure if applicable.

[Peter Apps]

Hi Rebecca

I forgot to ask, are you injecting split or splitless ?

Increasing the pressure just to make the solvent peak narrower is not a good idea.

Peter

[edmgc7788]

hi, thank you answering my question
my inject is spiltless. I just wonder in the same condition, same type column, why only back has this problem? i run sample in the same condition, so i don't think i could change the back condition which is different from the front.
it's possible cause by liner. Because recently our company used new liner which could be recycle. The wool is longer than before. i think maybe that cause discrimination. sometimes it's good, sometimes it's worse.
thanks again
rebecca chen

[rwjohnson]

Rebecca,

My first thought is whether or not the liner (and glass wool) has been deactivated. This could cause very bad tailing with certain analytes like amines and alcohols.

I'm not use of working with recycled liners, but I would think that packing inconsistancies would cause tailing too. You might try the same liner in both front and back to rule out liner?

Ron J.

[AICMM]

Ms. Chen,

I would investigate two things. First, if the tailing is really bad, it is possible that your split valve is never opening. This should happen after about a 1/2 minute and you should see a sharp drop in the solvent peak at that point. You may have to greatly expand the solvent peak to see it. You should also be able to see the split flow out the vent (on top) jump dramatically.

Second, I would be suspicious of too much wool. I have seen this in the past where there is a lot of tightly packed wool. Try trimming away 1/2 the wool and expanding it and see if the problem goes away. (Of course this does not apply if you are using the same liner on both sides.....)

Best regards,

AICMM

[edmgc7788]

Thank you all people answering my question
I will try to take out some glasswool and to see if it's better or not. Sometimes, when the liner was change, at the first couple days, tailing is more worse. After runing some samples or rinse, it's getting better.

Have any analysts used the double side gold seal? i am doing the test right now. Is any suggestions i can share?
thank you again

rebecca chen