Dear members, I could not explain APCI-MS for squalene. There are two M/Z, 411 and 440. 411 should be M*H+, but where is the 440 from? The mobile phase is IPA, Methanol with ammnium acetate. Thank you all. Michelle Add a Message This is a private posting area. A valid username and password combination is required to post messages to this discussion. Username: Password: