problem with baseline

[munio]

Can you help me I have a little problem my baseline i GC 6890 start at 25 pA now it is starting at 45 pA it strange till no I thought that 25 pA is too much but I couldn't done enything ofcourse I used a trap change liners cut column and many other things, please help me!!

[Mark]

Munio,
Hard to say where to start, there are many things that can raise the baseline. Make sure that the detector temperature is not above the max temp for the column, you don't want to bleed phase into the detector. Another possibility is that something eluted through the column into the detector and ahs contaminated the collector in the FID, might give a fairly constant higher background signal. Do you analyze TMS derivatized compunds?, maybe thay have contaminated the detector also. More info an the compounds you have put through the instrument might help with the problem.

Regards,
Mark

[munio]

Thanks a lot Mark

[Ron]

Try removing the column from the detector and sealing the bottom with a column nut and no hole ferrule, then compare the baseline signal with the signal with the column installed. If the baseline stays the same the detector is contaminated. If the signal drops with the column removed then the contamination is coming into the detector through the column. Once you determine where the contamination is coming from you can start to solve the problem.

Good luck.