Many lipids have a free carboxylic acid group that typically requires a weak acid mobile phase to ensure retention by HPLC. Unfortunately, the presence of the acid in the mobile phase also suppresses anion formation and often leads to poor electrospray ionization and poor MS sensitivity. Cayman"s AMP+ MaxSpec(TM) Kit contains a positively charged reagent (AMP+) that can be coupled quantitatively to free carboxylic acids through an amide bond linkage. The resulting derivatized product thus contains a positively charged group that shows improved electrospray ionization and consequently improved MS sensitivity. Cayman"s derivatization reagent is stable to MS/MS fragmentation and thus isobaric derivatives undergo compound-specific fragmentation to give unique fragment ions.