Chromatography Forum

We have an older Autotrace ( going on 7 years). Starting in Feb every extract has what NIST says is undecane in it. I am in the process of testing everything I can think of and have no clear answers as yet. The closest I've come to finding it is when I blow down 1:1 EA/ MeCl that has been collected from the sample pathway ( thru sample lines, pumps ect.) I get a trace of the undecane and quite a siloxane peak ( thru all 6 channels). I'm gearing up to redo this test using MeOH in case the mystery peak is polar.
And yes I've tested solvents, blow down equipment, different N2 tanks, multiple SPE lots .
I'm left thinking maybe my pump heads are breaking down.

Anyone seen what I am?

I've never used one but based on the steps you have taken I would say you are right to assume it's in the pump somewhere. The AutoTrace specs say it's a ceramic head etc., but I'm sure there's a rubber gasket somewhere that must be coming in contact with your sample now. Are you using teflon tubing etc. or other? Do you have any "rubber" parts inline, perhaps of the aftermarket sort?

I would assume that over time EA:MeCl2 could degrade certain parts. The vendors specs say not to use Acetone at all through the pump system and I think EA:MeCl2 would be similar in polarity/degradation potential. Please correct me if i'm wrong about any of these statements because I'm fairly unfamiliar with this system.

All my parts are from the manufacturer. The unit was rebuilt 24 months ago. That included all new piping, new syringes and a new 12 port rotor ( I think). A sample solenoid was replaced as it had a small leak.
Nothing was done to the pumps . I was told the only time pumps are dealt with is if they are not working.

Ummmmmmmmm
Update. I'm embarased to say thet it seems that the alkane is from our methanol. I changed lots when the compound showed up! It still is in a fresh bottle recieved 2 days ago.

May be changing suppliers.

Ahhh... Makes sense. I am also currently chasing some solvent contamination issues. However, mine are contaminated with my analytes through some human error of someone in my lab (myself being the only one).

I've had good luck with EMD chemicals in the past. They seem to be both cheap and clean.

Ah yes, why is it always the last thing checked ?
I concentrate 25 mls to about 1 to check my Ea and MeCl before use but not MeOH! Assumed ( there's a gotcha) since MeOH passed through the bed without being collected I would be fine, ha didn't think of what the MeOH would leave behind. Plus have been using the same MeOH fore more than a decade with no issues ( that I was aware of). The unit uses about 5-8 mls of MeOH to wet the bed and I add 5 ml to each sample as well.
I tested some P&T MeOH I use for 524 and it is fine. I'll be switching to this MeOH.

As far as the Autotrace solvents the manufacturer said I could clean with acetone as long as it is rised away with another solvent right after.

Follow up question.
I have been using Fisher Optima ( A 454) for years without issue. The two latest lots I have contain this contaminant. Has anyone else seen what I am?

For the time being I'll be using my B&J volatile grade MeOH.