On-line conversion and determination of aspirin using a flow injection-capillary electrophoresis system

A novel, rapid, and simple capillary electrophoresis (CE) method has been developed for the determination of aspirin by on-line treatment with alkali. Such on-line reaction with 0.20 mol/L NaOH solution for 2.5 min at 45degreesC automatically and reproducibly converts aspirin into its hydrolysis product salicylic acid. Analysis is carried out in less than 12 min after conversion of aspirin in a flow injection (FI) system coupled to a CE instrument via a split-flow interface cell, and a sampling frequency of 9 h(-1) is achievable. The on-line conversion method has been used to determine aspirin in four commercial pharmaceutical preparations, and the results are satisfactory.