why got weired strong baseline after replacing column

[xueshisx@gmail.com]

Hello everyone,
I just replaced second column for our instrument since I have peak tailing for the 2ed dimension. now I only run a pyridine. However, it seems I got a much high intensity solvent line. and the second dimension retention time also shift. What's the possible reason for this?
I use DB 5MS for 1st column, DB 17 MS for the 2ed column.
when I inject nothing, it also have a very strong intensity solvent line.

[Peter Apps]

My guess at the most likely cause is that you had a leak before you changed the column.

Peter

[xueshisx@gmail.com]

My guess at the most likely cause is that you had a leak before you changed the column.

Peter

Thanks, now there is no leak for the system, I baked the column for 1 hours. It still have problem

[Peter Apps]

Did the second dimension retention get longer or shorter ?

Please do not answer by editing the first post.

Peter

[xueshisx@gmail.com]

Did the second dimension retention get longer or shorter ?

Please do not answer by editing the first post.

Peter

It is longer than replacing column before.
it is the similar between injecting pyridine and inject nothing

[Peter Apps]

Did the second dimension retention get longer or shorter ?

Please do not answer by editing the first post.

Peter

It is longer than replacing column before. So not a previous leak that is no longer there then. Maybe a piece of ferrule in the end of the second (or first) column ??
it is the similar between injecting pyridine and inject nothing How are you measurine second dimension retention ? -if you inject nothing then there is no retention to measure ?

Are you sure that the new 2nd column is the same length, diameter and film thickness as the old one ?

Peter

[xueshisx@gmail.com]

Did the second dimension retention get longer or shorter ?

Please do not answer by editing the first post.

Peter

It is longer than replacing column before. So not a previous leak that is no longer there then. Maybe a piece of ferrule in the end of the second (or first) column ??
it is the similar between injecting pyridine and inject nothing How are you measurine second dimension retention ? -if you inject nothing then there is no retention to measure ?

However, when I inject nothing, there is still a strong solvent line on the image(so I can check the retention time). It looks like it has very strong baseline.

Are you sure that the new 2nd column is the same length, diameter and film thickness as the old one ? the length probably a little bit longer. others are the same

Peter

I don't know why I cannot attach image here.

[Peter Apps]

How long was the original 2nd dimension column, and how long is the new one ? What was the old retention time and what is the new one ?

To measure retention you have to know the difference between the injection time and the time that the peak elutes. If you have no injection you cannot have an injection time. What exactly are you doing when you "inject nothing" ?

How are you measuring the retention of only the second dimension column ?

When you say "solvent line on the image" are you referring to a peak on a chromatogram ?

Peter