Integration Methods for TPH/ TRH using GC-FID
Posted: Thu Mar 17, 2011 10:12 am
I've seen many different techniques for integrating the bands in total petroleum hydrocarbon analysis and some I think are not correct. The reason for this thread is for people to comment on their methods for integrating the hydrocarbon bands. Some examples of those bands are C10-C16, C17-C26, C27-C36 or >C10-C16, >C16-C34 and >C34-C40 and other variations. I have two methods and each has advantages.
1) A consistent feature of the chromatogram is picked out prior to the solvent peak. The intensity value (y-axis) is noted and each band is integrated horizontally at that intensity. A blank must be used to subtract extraneous peak area not associated with hydrocarbons. This is an easy method but has a little bit uncertainty associated with the intensity that the chromatogram settles to after the solvent peak and also slight drifts up and down.
2) The chromatogram intensity just before C10 is chosen so the start point and several minutes after C40 as the end. The integrated baseline does not need to be horizontal but must be straight and generally goes through the chromatogram baseline. Each band is integrated based on recording X and Y positions when the whole chromatogram baseline is drawn and then integrating each band based on those pre-recorded coordinates. The downside is that I think a little of the lower molecular weight bands is slightly reduced - generally is more fool-proof than option 1.
Please provide tips and integration methods for comment.
1) A consistent feature of the chromatogram is picked out prior to the solvent peak. The intensity value (y-axis) is noted and each band is integrated horizontally at that intensity. A blank must be used to subtract extraneous peak area not associated with hydrocarbons. This is an easy method but has a little bit uncertainty associated with the intensity that the chromatogram settles to after the solvent peak and also slight drifts up and down.
2) The chromatogram intensity just before C10 is chosen so the start point and several minutes after C40 as the end. The integrated baseline does not need to be horizontal but must be straight and generally goes through the chromatogram baseline. Each band is integrated based on recording X and Y positions when the whole chromatogram baseline is drawn and then integrating each band based on those pre-recorded coordinates. The downside is that I think a little of the lower molecular weight bands is slightly reduced - generally is more fool-proof than option 1.
Please provide tips and integration methods for comment.