contamination

[natalie]

we perform esterification of fatty acids using acethyl chloride. I am finding contaminating peacks even in a blank sample (with or without addition of the internal standard). Contaminating peaks appear to be stearic and palmitic acids. We performed deep cleaning and maintenance of the instrument. Any ideas?
Thank you.

[Don_Hilton]

Start with a run with no injection at all, just push the run button, as if you are doing a manual injection. This will let you know if the problem is in the GC or if it is injected into the GC.

[chromatographer1]

Please detail the GC and the 'deep cleaning' you mentioned. Different GCs are prone to different issues.

Rod

[Peter Apps]

Hi Natalie

If these are genuine contaminants, as opposed to carryover, then by far the most likely source is fingerprints on apparatus. Carryover and contamination can occur together of course.

Peter

[natalie]

Thank you for the replies. We think the contamination may derive from the tubes or caps. We use borosilicate glass tubes with polipropylene caps. Do you know any alternative tubes and caps?
Thank you.

[Steve Reimer]

Do you have "Hand Soap" in the lab? A common source for these.