PerkinElmer 350 ATD -- Reproducibility??

[rubyfan]

We had a PerkinElmer 350 automated thermal desorption system connected to an Agilent 6890 with 5973 MSD. We are experiencing considerable issues with peak size reproducibility. We've tried spiking several tenax tubes with 1uL of the same standard and the peak area variability can range from 10-30%. Just wondering how other users of this system have found reproducibility to be? In general, we've found the system to not be that great. The o-rings, even though they are supposedly the highest quality perfluoroelastomer o-rings that PerkinElmer provides, bleed terribly. We always gets at least 5 or 6 peaks with area counts >15,000,000 per run, and these peaks are attributed to o-ring bleed from the PerkinElmer ATD. This is still after weeks of conditioning the o-rings, and several replacements.

Anyway, if anyone has any thoughts on reproducibility with the ATD, please let me know.

Thanks,
Aaron

[MikeD]

Aaron

Do you have evidence on another system that you can spike Tenax tubes with good repeatability ? On our Perkin Elmer 650 system it's normally < 1% rsd spiking aromatic hydrocarbons in 5 ul methanol. Could you give more details of your spiking method, such as purge volume, flow etc. and what you are trying to measure.

I can't help with the bleed problem. I have never seen it on our system.

[MikeD]

Aaron

Do you have evidence on another system that you can spike Tenax tubes with good repeatability ? On our Perkin Elmer 650 system it's normally < 1% rsd spiking aromatic hydrocarbons in 5 ul methanol. Could you give more details of your spiking method, such as purge volume, flow etc. and what you are trying to measure.

I can't help with the bleed problem. I have never seen it on our system.