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- Posts: 7
- Joined: Thu Feb 20, 2014 5:13 am
I´ve been recently injecting quite a lot of standards with a GC-QqQ system and I´m facing some interesting issues with amino acid standards; when I start working with amino acids I get a nice peak(s) from the first injection but then nothing from the second one, even if I´m just re-injecting the first sample. If I inject something different, such as fatty acids, for while I again get a nice peak(s) from the first injection but nothing from the following injection. Peaks in the first injection are nice and sharp, no fronting or tailing and no detector saturation. Injector is performing as it should be as I have no problems with other classes of chemicals. I´m using Rxi-5Sil MS column. For derivatization I´m using methoxyamine and MSTFA.
Any ideas on what I might be doing wrong?
So far I have tried to:
- change liner (RESTEK deactivated)
- change septa
- vary sample concentration
- use deactivated vials
- different split value
Cheers,
Otto