主题：【讨论】lcms problems

I have some questions about sensitivity and stability of LCMS.(Thermo TSQ Vantage)

Question 1:

An analyte can be recognized in optimization, but it cannot be detected when run the LCMS.

Ways that I tried :

-tried new mobile phase, standard, column

-removed the column and inject directly

-optimization again

-changed the collision energy

- injected the sample with and without sample pretreatment (same as hk)

Question 2:

After a few days,Another analyte ‘s area decreased significantly after an overnight injection. It was good before. However, its d8 internal standard is still normal.

Ways that I tried :

-prepared new standard

-changed the gradient

-injected without column

-clean and sonicate the MS

-bake the ion source

Question 3:

All analytes' stability is not very good when injecting the same sample many times.

After trying the above methods, the problems are not solved yet. And the engineers can not tell the reasons as well, especially Question 2. I am looking forward to seeing your reply. Thank you very much.