sample not injected!!

[che313]

I try many times but it's repeating!!
I extract THC from urine and dervtize with BSTFA
alaways it gives clear TIC no chromatogram at all. All other samples are ok!!

GC-MS: Agilent 6980N, MSD 5975B
Column: HP-5ms, 30m, 25 id, .25 thick
Inection 250 C 2uL
Carier He 1ml/min

[Consumer Products Guy]

If all your other samples and standards are OK, I'd suspect too much water carried over in your extraction, using up all your BSTFA reagent. I'd increase the ratio of BSTFA to samples; if you don't see too much with m/z 73 in your sample, you didn't have enough derivatizing agent to overcome the amount of hydroxy compounds in your sample, usually water.