TO-15 Calibration Problem

Discussions about GC-MS, LC-MS, LC-FTIR, and other "coupled" analytical techniques.

3 posts Page 1 of 1
Hi all,

Our lab has been running TO-15s for a number of years, successfully calibrating 0.05-50ppbv with little issue. One instrument even had a calibration last 4 years. We now have to routinely drop the 50, 20 or even the 10ppbv point for many heavy weight compounds including BTEX. We see complete saturation at these levels, with no difference in response. This is across 5 systems, and this only started about two years ago. Entech7200/7890/5975c. We also have other preconcentrators, a 5973, etc.

I can guarantee what we're seeing is not column or analyzer overload. I'm convinced it's something with the preconcentrator, either bad traps being overloaded, or heated/cooled zones not working properly. Any suggestions would be greatly appreciated.
Regards,

Christian
Has the electron multiplier been recently changed or is it old?

If it is old and running at a higher voltage, then you will lose some linear range and will saturate more quickly.

If it is saturating the column instead of the detector, you may want to look to see if the split/splitless inlet is working properly and giving the amount of split you are expecting or closing the splitless valve when it is supposed to and not sticking or leaking.
The past is there to guide us into the future, not to dwell in.
Would we see saturation for only high MW compounds? The EM has not been changed recently and I couldn't tell you right now what they're running at. I suppose I could swap one out for a new one and see if there's improvement. I work with two mass specs daily and what I'm seeing is completely new to me. Some compound responses actually drop off the higher the concentration which seems like trap breakthrough. We're running a couple tests to try and determine if there's a heated zone problem in the preconcentrator.

I'm curious if the split vent has anything to do with this type of "injection" because it's a heated transfer directly to the analytical column inside the oven. I would think problems with the split vent or inlet would only present itself with flow problems and retention time shifting.
Regards,

Christian
3 posts Page 1 of 1

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