Flow injection chemiluminescence determination of medazepam

A new flow injection chemiluminescence method for the assay of medazepam is explored. The method involves the use of permanganate in sulfuric acid for the oxidation of medazepam with the emission of chemiluminescence detected by a photomultiplier tube. A simplex procedure was employed for optimising the conditions for high sensitivity detection, which were found to be 1.03 × 10^-3 mol L^-1 permanganate, 0.153 mol L^-1 sulfuric acid and 3.43 mL min^-1 flow rate. The linear calibration range was 3.7 × 10^-5 to 1.7 × 10^-3 mol L^-1. The detection limit (3σ) and the sample throughput were 1.85 × 10^-5 mol L^-1 and 100 per hour, respectively. The relative standard deviation for 5 replicate determinations of 1.9 × 10^-4 mol L^-1 medazepam was 0.15%. Common excipients (starch, glucose, maltose, lactose) used in pharmaceutical preparations had no effect.