I am derivatizing GSH with ABD-F to make the glutathione fluorescent. I am using TCEP to reduce GSSG. When I run a blank control with just water (ultrapure) instead of GSSG the TCEP appears to react with ABD-F and produce several new fluorescent products seen on UPLC as different peaks. The TCEP is in borate buffer. These side reactions were totally unexpected and frustrating. Any thoughts?