Alkane contamination on a 6890 FID.

[Stunt]

Irritating contamination in the C20 - C40 range coming from our lab, in processed samples and blanks. I don't believe it's the instrument/gas/vials/solvent as air injections and unprocessed solvent injections are clean. Looks like fish-fin style polysiloxane septa contamination, but it is absolutely alkanes as confirmed by FID and GCMS methods. Dozens of tests inconclusive, as this stuff seems to be in everything, and is sporadic in concentration but getting worse. Has anybody seen this particular stuff before? It is provoking my ire.



Thanks,
Stunt

[Steve Reimer]

We have had problems like that where a wash bottle in the prep area was contaminated with some oil from the air. It was in quite a few samples before it was found. I can't remember the source, but it seemed odd at the time.

[seamoro]

We had the same problem. Have you tested your gloves? Your gloves your lab tech/chemist wear are in contact with everything. Thats what happened with us! false positives everywhere!. The main scource of the contamination for us was that technicans were folding filter paper with gloves on and that was the main scource!

[Stunt]

Thanks seamoro/Steve. Yeah, we tested the hell out of the gloves, and it was there. Even when we were testing without using any gloves its there. It's really bugging me, and starting to impact quality.

Anybody else?

[Peter Apps]

Do you by any chance have a vacuum pump whose outlet is venting to your lab air ? Or is anyone using house compressed air ?

Peter

[seamoro]

What are you doing your extractions with? Glass or plastic?

[lynoguchi]

Stunt,

What are the samples?
What is the GC configuration, inlet, column?
This contamination appears in the first injection after a standby period?