8270 Calibration Problems

[ae]

I have a 5890 with a 5972 MS. I run sem-volatiles on this instrument with a RESTEK RTX5-MS column. I have recently replace this column with a new one (same type) and cleaned my source (I have also had a service call recently). Now when I run calibration, all of my PAH's, phthalates, and some pesticides are going quadratic. Any suggestions?
Thanks,
Amy

[Ron]

It sounds like you are overloading either the column or the ion source. The 5972 has a somewhat limited linear range, and if you exceed this range the curve have lower response factors at high concentration, and may give a better fit with a quadratic curve. If you are doing splitless injections raise the column in the liner about 5 mm. This allows less material on column and may resolve the problem.

[Answer Man]

From my experience, quadratic curves are caused by not enough sensitivity at the lower conc's. An inverse quadratic curve (flatter at the higher conc's) is usually a sign of overload.

In addition, most instruments are fairly linear up to a 40-fold calibration range, anything larger may be exceeding the instruments limit.

[ae]

Thanks for the help. I repositioned the column a little higher in my inlet, and that helped the PAHs and phthalates a bunch. I have some other problems now, but I will repost as a second question.
Amy