No signal at negative mode

[Jasmine]

Dear All,

We are using an API2000 in our lab. Recently, we encountered a "weird" problem. During the tuning of a certain compound, we tried to do both positive and negative mode. Our signal with positive mode is very good. However, we didn't get a signal using the negative mode. Even running the solvent alone did not produce even a tiny bit of signal. Could you please advice what the probable cause could be? What should we do?

Appreciate any advice. Thanks!

[gmnydn]

I suggest you to conduct diognostic tests for quadrupoles if there is of your instrument. There may be problems in DC energy ramps of Q1 and Q3 for negative mod.