FLOW-THROUGH POLAROGRAPHIC CELL FOR FLOW-INJECTION ANALYSIS - DETERMINATION OF NIFEDIPINE IN PHARMACEUTICAL FORMULATIONS

A simple design of a polarographic flow-through cell is proposed in wh ich a conventional dropping mercury electrode (DME) is used as working electrode, and a mercury pool and a platinum wire are used as the ref erence and counter electrodes, respectively. The mercury droplets fall ing from the DME coalesce with the pool, and a fairly constant hold-up cell volume is achieved by controlled removal of the mercury from the pool at an equivalent flow rate than that of the DME. The analytical features of the cell are illustrated by flow-injection (FI) determinat ion of the nitro derivative nifedipine in pharmaceuticals. The flow-th rough defector can be used either amperometrically, under continuous f low operation, or voltammetrically in quiet solution, under continuous flow-stopped flow mode. Under continuous flow operation of;he eel!, t he sampling rate obtained was 120 h(-1). The repeat-ability of the ana lytical signals, expressed as RSD, was always lower than 2.1%. The rec overy of nifedipine in synthetic tablet formulations was 99.8 +/- 0.6% . (C) 1997 John Wiley & Sons, Inc.