Reducing and Oxidizing Columns in the Flow Injection Determination of Nitrazepam in Pharmaceutical Formulations

Abstract

Two flow injection analysis (FIA) systems for determining nitrazepam (NZP) in pharmaceutical formulations using two kinds of solid-phase reactors were developed. The first system involved on-line oxidation of the reagent using a mini column containing PbO₂ immobilized on cellulose acetate, while the second one involved on-line reduction of drug using a mini-Jones reductor. Both methods are based on spectrophotometric method involving oxidative coupling reaction to phenothiazine with reduced NZP in the presence of a suitable oxidizing agent to form a green color product measured at 615 or 589 nm for the two methods, respectively. The calibration graphs were linear over the range 0.5 to 45 and 10 to 250 μg/mL with a relative standard deviation less than 3.6% (n = 32) and 2.4% (n = 35) for the two methods. Solid-phase reactors can be applied for the determination of NZP in a FIA with high sensitivity and significant advantages over conventional procedures.