Curve flattening 8270E
Posted: Tue Feb 24, 2026 7:17 pm
Hello,
I'm running 8270E analysis on a 6890A GC and 5973 MS. Splitless injection. I just installed a brand new column and did source maintenance, like I have done a million times before, and I'm getting some really odd lines of fit for my curves on analytes that I don't normally have trouble with. I had a couple of ideas that I wanted to run by anyone here:
-My response values have been in the process of skyrocketing over the last year. A year ago when I changed a column, the response of the last analyte on my list had a response value of just over 3,500,000 on the high point of my curve. On the curve I ran yesterday, this value was 7,500,000. The earlier eluting analytes of my curve are raising, too, but not nearly as high. I think it's worth noting that that later eluting compound curves look better (still not great though), despite me using that as an example. The naphthalene photo I provided is just the worst example of my normally good looking PAHs.
-My repeller value is kind of high, at 34.81 on the DFTPP tune that I did, so I am going to switch that out.
-It's also been a second that I've changed the split-vent trap, so I'm changing that, too.
-I read up on posts on various website about curve flattening and they mentioned that I could be oversaturating my source/column. I find that hard to believe since I have been making the same curves and running on this same instrument for almost 5 years now. Don't know why/how I could suddenly be doing anything different, but I could obviously be wrong.
-I admittedly have an air leak somewhere. I've been trying to nail it down for a while now, but everytime I think I get it, I don't. This could obviously be the root of all issues, but in the time I've had this leak, I've not had my curves be this bad.
Thanks
I'm running 8270E analysis on a 6890A GC and 5973 MS. Splitless injection. I just installed a brand new column and did source maintenance, like I have done a million times before, and I'm getting some really odd lines of fit for my curves on analytes that I don't normally have trouble with. I had a couple of ideas that I wanted to run by anyone here:
-My response values have been in the process of skyrocketing over the last year. A year ago when I changed a column, the response of the last analyte on my list had a response value of just over 3,500,000 on the high point of my curve. On the curve I ran yesterday, this value was 7,500,000. The earlier eluting analytes of my curve are raising, too, but not nearly as high. I think it's worth noting that that later eluting compound curves look better (still not great though), despite me using that as an example. The naphthalene photo I provided is just the worst example of my normally good looking PAHs.
-My repeller value is kind of high, at 34.81 on the DFTPP tune that I did, so I am going to switch that out.
-It's also been a second that I've changed the split-vent trap, so I'm changing that, too.
-I read up on posts on various website about curve flattening and they mentioned that I could be oversaturating my source/column. I find that hard to believe since I have been making the same curves and running on this same instrument for almost 5 years now. Don't know why/how I could suddenly be doing anything different, but I could obviously be wrong.
-I admittedly have an air leak somewhere. I've been trying to nail it down for a while now, but everytime I think I get it, I don't. This could obviously be the root of all issues, but in the time I've had this leak, I've not had my curves be this bad.
Thanks