PBDE on GC-MSMS

The lower masses are fine and all peak shapes look nice.

I can give those suggestions a try when I get things back up and running. I am experiencing a sensitivity loss and need to figure out if it is standards, or the new column I installed.

If the lower mass peaks are fine...it's not a mass spec problem.  OK, it's 99.9% that it's not a mass spec problem as long as the temperatures are correct. 

Are the higher mass peaks reproducibly higher?  Maybe make a new batch of standards...taking all the care required. The person I know running PBDEs says that most issues he sees have come back to standards. 

Thanks again. 

We resolved the issue of sensitivity, a bad column (although brand new). The patterns of the PBDEs weren't what they should be. After much testing we concluded the column has a defect. I have now installed a different column that we had on hand that is different than the previous but still one suggested from an Agilent application. 

With the mass-labelled standards, I did get a chance to try upping the source to 325C and didn't have any luck (even with this other column - I did test on both). I can give a try to the injection parameters next week (I tested it on the "bad" column with no success).

I did try to inject a standard with ONLY mass-labelled vs a low standard and found that it looks like enhancement happens even with a minor amount of native added. It isn't very noticeable with the lower congeners but definitely when they get higher, around the Hepta - Deca.

When we run a full calibration there is a slight increase in area counts for the lower masses but nothing like the high ones. The low masses it can only be noticed between the low and high standard but with higher congeners, it is a positive linear response between all the calibration points.

The peak shapes all look great with baseline resolution for everything in the test mix.

I did a few more experiments today with no success.

Decreased the time on the pulsed pressure program and the oven temperature to allow more equilibration time

Tried the source at a hotter temperature (325C) - Last week

Started using a new column (HP-5MS vs HP-Ultra1) - Last week

Tried to use the back inlet of the 8890 and did a spitless injection (isocratic temperature)

There is still the difference in the high congeners (Hepta-Deca) with all these tests for the mass-labelled analytes, increasing as the concentration of the native increases. The mid and low ones seem fine still, reproducible.

Two different type inlets are the same. The early eluters are good. The method looks reasonable. The tunes are good.   I'm sorry, but I think we've exhausted about all we can do here on this forum.  The next step would be to contact Agilent (Contact Us)  and setup a consultation with someone who can look directly at your sample preparation, methods, and the data on your system.    There is every chance that this is normal for these compounds, too, and someone who knows that would be the best person to answer.

Thank you for your patience and persistence.

Hi,

I went ahead and ordered the 6mm extractor lens. Unfortunately, it isn't compatible with the HES source (I might've forgotten to mention). Nonetheless, there is only a 4 mm available for the HES, would this still be worthwhile?