I'm trying to identify melatonin and seratonin. When I run the standards, each one has it's respective peak but it's the molecular parent ion, not a fragmentation that shows up. I'm currently using ESI as the ion source, but it seems like APCI may be a better fit given the problems I've run into. Before purchasing the APCI ion source, I want to know if there are other ways to trouble shoot this issue, with changing parameters, etc. Thank you!