Greetings,

I run one of our drug molecules on Waters LC/MS, and did not have any MS trace signals even with UV trace of about 1.6 V signal.

moble A: 0.05% TFA
moble B: ACN
MS + mode

Please let me know possible reasons for this lost of MS signals. Is it because some molecules are extremely hard to ionize? I cleaned cone and cone gas nozzle, but still did not get MS signals.

Thanks a lot