Strange Response Factors

[Tristan]

G'day All!

I am currently trying to optimize a derivatization method for 3,5,6-trichloro-2-pyridinol (TCP) using GC/MS. I have TCP and pyrene (IS) in toluene and add MTBSTFA and then allow this to react for 45 mins at 60 degrees and inject 0.5 microlitres in splitless mode (0.5 min hold time). I am using a DB-5ms column. I have found that on the first injection my RRF is about 1.2 and then this decreases (to ~1) in following injections. Any ideas on what could be causing this?

Thanks in advance!!

[Peter Apps]

Hi Tristan

Most likely the derivative is unstable.

Peter

[chromatographer1]

Tristan,

Since the peak area for TCP is increasing, the most likely reason In My Humble Opinion (IMHO) is that you are deactivating sites in the injector or column that are decomposing the derivitive or that the reaction is not complete at the first injection but continues and is completed for later injections.

Best wishes,

Rod