Chromatography Forum

Or not?

My guess is you have a hit. It is not unlikely to have co-extracted material cause peak shape degradation or RT shifting (almost always later).

To verify, I would spike the sample with 1260 to approximately double the concentration in the extract. If the peaks are doubled (and my bet is they will be), then it's the PCB, if you see both sets of peaks, then it's clearly something else. I once saw a biphenyl sulfide material that eluted about the same time as the PCBs, but without a pattern match, ran it on an ELCD and the peaks disappeared.

A few things to remember with waste analysis, you also have 1262 and 1268 out there, and at times DCB was used on its own.

Greg

Agree with gpronger that you probably have a hit. However, you still have to prove it. Imagine explaining to an auditor the basis for calling it based on my opinion..... I'm so glad I don't do that anymore. Also agree with gpronger that an overspike makes a lot of sense.

You might also think about just diluting the sample a bit. Comparing 10 ppm to sample, it looks like you have enough signal to do that. Also, is this after cleanup?

Finally a comment. You seem to have some tailing on your peaks which makes me wonder about your injection and initial temp. Do you mind posting those conditions.

Best regards.

Also, is this after cleanup?

No cleanup on this - it was an oil sample if you're curious. I just did a quick sulfuric acid wash and extracted with hexane.

Finally a comment. You seem to have some tailing on your peaks which makes me wonder about your injection and initial temp. Do you mind posting those conditions.

Inlet temp 250C
Initial temp 170C

5C/min to 260C hold 2 mins
10C/min to 280C hold 5 mins

I did spike the sample with 1260, and I would say it's a hit (Tried to post a screen shot, but something's wrong with my network here). This is one of the first samples I analyzed where I really questioned it - (that is, it didn't look EXACTLY like a 1248, 1254 or 1260 standard).

Thanks,
John