stearic and palmitic contamination during lignin analysis

[CanuelLab]

In our lab, we run many FAME's, sterols, alcohols, and alkanes through a DB_5MS column on a 7890AGC/5975CMS. Recently we have begun to analyze lignin. When the standards are shot, we are not seeing any peaks for the internal standard, but we are seeing a stearic acid peak, a palmitic acid peak, and many alkane peaks. The samples/standards are shot in a pyridine solvent with BSTFA. When we shoot the pyridine by itself, we dont' see any of these peaks, when we shoot hexane we don't see any of these peaks, when we shoot other standards in any other solvent we don't see any of these peaks, it's only in these lignin samples. I don't think it's a product of the BSTFA in the sample because we use BSTFA in our sterol samples and have never run into this issue. None of the standards are expired (and everything in the lab is glass, no plastic is used anywhere, however we do where nitrile gloves).

Samples shot about a year ago never had any of these issues, it has just presented itself recently. Nothing is different in the process so the source of the contamination is a mystery.

If anyone has any suggestions or thoughts as to where this kind of contamination could come from I would greatly appreciated the feedback!! Thanks!!

[dhdh]

What range or fraction are the alkane peaks...are they mainly n-alkanes?
Could those 2 FA's come from fingerprints? (if it was fingerprints, you'd also get smaller peaks for cholesterol and squalene.)

What form is the lignin in (anhydrous white powder?), how pure is the material? Lignin, isn't that what makes old newspaper turn yellow?

[Don_Hilton]

Run the full procedure with and without lignin in the samples. Could it be the lignin? Do you have a sample from another source and is there risk that the sample has been contaiminated, particularly if it has sat for a year? It has been known for the "clean" spatula to move around the lab - and leave a trail.