Chromatography Forum

Is MeOH your solvent or is it an analyte? What solvent are you using? Liquid injection? Why such a high inlet temperature? Highest temp your column is rated to (program temp)?

You can try using a 1 meter piece of 0.25mm retention gap as the restrictor column, or if you don't have any uncoated tubing, a piece of a wax column with 0.25mm ID.

I have used up to 3 meters of restrictor tubing.

best wishes,

Rod

thank you
my problem is still there. my column is new and recently both back and front show the tailing. Today i change the gold seal, liner and clean the inlet. My instrument setup is the same as ohters. I use splitless and temperature programme. My column is DB1. Before this year, i don't have this problem. I feel so frustrated.
Can you tell me what should i do ?
thank you
rebecca

Can you tell me what should i do ?
thank you
rebecca

Hi Rebecca

Take the time and trouble to read back through the thread and answer the questions about your setup and procedures that have been asked of you. Nobody can solve your problem if you do not provide the necessary information.

Peter

Rebecca,

It seem this topic got a little confusing since people started answering Mike's questions as well. However, Peter is right that we need a little more info. It was mentioned earlier that the split-vent line (copper tube on 6890/7890s) and the trap at the end of it may be contaminated. You said you would look into that possibility. Have you looked at it yet or cleaned it? If not then at the very least remove the copper line and clean it with a series of different polarity solvents. I usually end with something volatile like acetone or methylene chloride then I gently heat it (no open flames!) to drive any solvent out of it and purge it with N2 or He for a few minutes before re-installing it. Chances are you have contamination in this line if you are running dirty samples.

Let us know where you are at.

Tailing peak...solvent....FID...i suspect 3 things:

- Column installation at detector is to short
- Leak at jet bottom
- Make-up flow is off or too low

hi,
according to suggestions you gave to me, i changed the vent filter and split vent line for both back and front . Here is my rinse(DCM:HEXANE=1:1). The problem is still there. by the way ,i scan the chroma, but i don't know how to post or attach it
There is another question: i am usign 5975 GC-MS. I use HS to inject sample(split ratio=50), sample to to one column which analyse c6 to c10, another column is connection MS. The initial tem is 60, aggetate tem is 90. I ran cals std very day. now the problem is i spike 50ul of 200ppm cals to a vial which has 10ml solvent used 20g sodium bisufate dissolve in 4L ioniazed water. I detect c6,c10 and toluene using FID. c10 is always low, sometimes is half response to c6 and toluene. I also spike 15ul of 200ppm to a vial which has 10ml same solvent. The all respond is close. I change gold seal, clean syringe,change liner and column, the problem is still there. Other instruments have the same problem,but it's not stable, sometime is good, sometimes is bad.
could you please give me some suggestions?
thank you so much
rebecca