Chromatography Forum

We have noticed an issue the signal graph generated by ChemStation. The GC it is connected to is generating a positive signal off of its FID in the range of tens of pA. We can bring up the relivant signal-in infromation in ChemStation that is likewise reporting values of tens of pAs. The graph is being drawn with a lower bound of -100 pA and the line representing the signal response stays below 0 pA, as though somehow 100 pA is being subtracted from our signal.

We have gone through the method and can see no evidence of any subtractions being done.

How to I restore the chart to reflect the actual signal values?

Did you check on GC that you don't have column compensation turned on. It is not method setting but instrument and during the run it will subtract current value from stored

Did you check on GC that you don't have column compensation turned on. It is not method setting but instrument and during the run it will subtract current value from stored

Yes, we checked the instrument settings too; I've always considered instrument setting part of the method, since that where ChemStation saves those settings. We do not have column compensation turned on.

Do you get negative baseline on online plot during the run or just in report? what if you chose test plot for signal, is it also negative?