4-(5,6-dimethoxy-2-phthalimidinyl)phenylsulfonyl semipiperazide as a fluorescent labelling reagent for determination of carboxylic acids in precolumn high-performance liquid chromatography.

A fluorescent labelling reagent, 4-(5,6-dimethoxy-2-phthalimidinyl)phenylsulfonyl semipiperazide, was designed for the determination of carboxylic acids by precolumn HPLC. The reagent was reacted with carboxylic acids at 100 degrees C for 15 min in the presence of an activating reagent (a mixture of triphenylphosphine, 2,2'-dipyridyldisulfide and pyridine) and produced highly fluorescent derivatives, which were separated on a reversed-phase column by fluorescence measurement at 317 nm (excitation) and 380 nm (emission). The detection limits were 4-12 fmol/injection. The reagent was used for HPLC assays of long chain fatty acids in human serum by isocratic elution.