Capillary electrophoresis with post-column addition of terbium and sensitized lanthanide-ion luminescence detection for the determination of diflunisal and salicylic acid

A detection scheme based on the Post-column addition of terbium followed by sensitized luminescence detection has been developed. Two model Compounds- saliculic acid and diflunisa- were separated by capillary electophoresis in an alkaline phosphate buffer. A Solution containing terbium and CTAB was added post-column via a “home-built” reactor resulting in the rapid fromation of the strongly luminescent terbium-salicylic acid and terbium-diflunisal complexes in a reaction capillary. Following complexationn in the reaction capillarty, the 325 nm line from a HeCd laser was used to excite the analytes which efficiently transfer their energy to terebium. Resuulant luminescence of terebium was liner of 2 orders of magnitude. This novel and practical system enables the detection of micromolar concentrations of diflunisal and salicylic acid- a 10 fold improvement over UV absorbance detection in the same system. Post-column addition of terbium also eliminates the problems associated with strong adsorption of the lanthanide ion to the silica walls of the separation capillary and the formation of metal-ligand complexes with different coordination numbers.