Development of a Flow Injection System for Differential Pulse Amperometry and Its Application for Diazepam Determination

This work presents the development of a flow injection system for differential pulse amperometry (DPA) for diazepam determination in the presence of oxygen. The thin flow cell consisted of the bare glassy carbon electrode, reference silver/silver chloride, and stainless steel as the auxiliary electrode. Electrochemical reduction of diazepam (DZP) was characterised by cyclic voltammetry. Azomethine reduction peak was used for DZP quantification. The detector response was linear in the range 20–250 µmol/dm3of diazepam, with a calculated detection limit of 3.83 µg/cm3. Intraday and interday precision were 1.53 and 10.8%, respectively. The method was applied on three beverage samples, energetic drink, and two different beer samples, and obtained recoveries were from 93.65 up to 104.96%. The throughoutput of the method was up to 90 analyses per hour.

Evaluation of a glassy-carbon electrode for amperometric detection of selected methylxanthines in serum after their separation by reversed-phase chromatography.

We examined the relative merits of direct-current, pulse, and differential pulse amperometry at a flow-through, glassy-carbon electrode used in monitoring column chromatography. We give a rapid, simple procedure for determining theophylline (1,3-dimethylxanthine) in 20--100 microliter of blood serum. Interference by 1,7-dimethylxanthine, a metabolite of caffeine, is compared for photometric and amperometric detection, and some advantages of combined photometric and amperometric detection are discussed.