Dual-stopped-flow spectrophotometric determination of amiloride hydrochloride in a multicommutated flow system Original Research Article

In this work a multicommutated flow system combining a binary sampling approach with a dual-stopped-flow strategy, for the spectrophotometric determination of amiloride hydrochloride in pharmaceutical preparations is proposed. The developed methodology is based on a two-stage reaction between amiloride hydrochloride and 3-methyl-2-benzothiazolinone hydrazone (MBTH) in the presence of Ce(IV) which is monitored at 545 nm. Reaction development is favoured by the intercalation of sample and reagent aliquots accomplishing a faster sample zone homogenisation with a low dispersion pattern. The sample zone is then halted for a certain period prior to detection resulting in an increased reaction time and a concomitant sensitivity enhancement. The implementation of a dual-stopped-flow manifold enabled the simultaneous processing of two samples, thus improving the sampling rate. Beer’s law was followed for amiloride concentrations of up to 120 μg ml−1. Results were reproducible (RSD < 2.2%, n = 10) and in agreement with those obtained by the reference procedure with relative deviations from −1.2 to 2.4%. A sampling rate of about 30 samples per hour was attained.