HAA5 Extraction

[ALO]

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

[bluejay]

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

[lovemymoe]

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...

[mjh32586]

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

[lovemymoe]

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

[bluejay]

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.

[mjh32586]

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??