Chromatography Forum

Hello, I am wondering if anyone has had experience running an HAA5 Extraction on an HP5890 Series II Plus GC. I am having trouble with the surrogate concentration. I have created a new calibration curve and the correlation coeff. for all the compounds, IS, and surrogate are above 0.995. However, when I run a extraction the surrogation concentration is extremely high. Can anyone provide any ideas or solutions as to why this is occurring. Also, I know that I have made the concentration correctly and I am not over adding the surrogate since I am using a 10-uL syringe.

Thanks, AL

Try analyzing a sample without the surrogate added to see if there is a peak at the same retention time as the surrogate.

i would love to hear if you've made any progress on this. we do them on a 5890 too and the issue has just cropped up in the last 5 or so batches but of course during a time that a few changes were made so we can't be certain why. our curves are great with spot on qc too but the samples just keep increasing as the sequence progresses. i can share more details if you're still working on it too...

are you adding the surrogate in the acid form and then derivitizing it?

yes, the surrogate is added prior to extraction and it's processed throughout the entire procedure.

See post above about analyzing a sample without the surrogate to see if there is co-elution. When I ran HAA's, I occasionally had problem bottles of MTBE that had new and different contamination, sometimes co-eluting with the surrogate. Just injecting the MTBE didn't show it, I had to run it through the derivatization process for the contamination to show up.

I have read that mtbe can be contaminated with peroxides which will show up as extra peaks in your chromatography. This could be what is causing your problem??