Column Bleed correction and integration

[rajaijah]

Hi guys, new to the forum.

I did go through few threads that related to the question I have but decided to post my question to get a better straight answer.

I use GC-FID for F24 heavy hydrocarbon fraction analysis (Oil in sample). I do keep a blank made of same solvent mixture as my sample and get the values for Column bleed corresponding to each fraction (F2, F3, F4). Than analyze my sample and integrate them with same method and subtract the column bleed.

When the sample is integrated automatically, it's not counting the area from the base line ( I mean zero) but from the valley of previous fraction. Do I have to manually integrate so I calculate the area from '0' ? I am confused because if I am going to subtract column bleed eventually shouldn't I also include the area below the valley all the way to zero so the column bleed subtracts it.

Please let me know if you guys need more info to help me here.

Thanks a lot guys.

[GasMan]

You need to give some details on the GC and Data system that you are using, as things may be different from supplier to supplier. In the Agilent 6890 and 7890, the column bleed is subtracted in the GC, and the resulting signal is then fed to your data system where the integration is carried out.

Gasman

[rajaijah]

We have a HP 6890 series GC and use Agilent MSD chemstation data analysis. Thanks