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

In this work a multicommutated flow system combining a binary sampling appr oach with a dual-stopped-flow strategy, for the spectrophotometric determin ation of amiloride hydrochloride in pharmaceutical preparations is proposed . The developed methodology is based on a two-stage reaction between amilor ide hydrochloride and 3-methyl-2-benzothiazolinone hydrazone (MBTH) in the presence of Ce(TV) which is monitored at 545 nm. Reaction development is fa voured 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 a n increased reaction time and a concomitant sensitivity enhancement. The im plementation of a dual-stopped-flow manifold enabled the simultaneous proce ssing of two samples, thus improving the sampling rate. Beer's law was foll owed for amiloride concentrations of up to 120 mu g ml(-1). Results were re producible (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. (C) 2000 Elsevier Science B.V. All rights reserved.