A pulsed sequential injection analysis flow system for the fluorimetric determination of indomethacin in pharmaceutical preparations

This works reports the development of a pulsed flow sequential injection analysis (SIA) system based on the utilisation of pulse generating solenoid micro-pumps, which replace the conventional solutions propelling units commonly used in SIA systems. The influence on sample/reagent zones interpenetration and reaction zone formation of the reproducible pulsed flow produced by micro-pumps operation, which is characterised by a chaotic solutions movement, was comparatively evaluated with the typical laminar flow conditions of conventional SIA systems. The enhanced sample/reagent mixing provided by the controlled pulsed flow was favourably applied in the implementation of a SIA methodology for the fluorimetric determination of indomethacin in pharmaceutical preparations upon alkaline hydrolysis in micellar medium. Linear calibration plots were obtained for indomethacin concentrations up to 10-5 mol l-1 with a 3σ detection limit of about 1.6 x 10-8 mol l-1. The obtained results complied with those furnished by the reference procedure (RD ≤ 2.3%) and exhibited good reproducibility (RSD < 1.2%, n = 15). Sampling rate was about 30 samples per hour