Flow injection-spectrophotometeric determination of some catecholamine drugs in pharmaceutical preparations via oxidative coupling reaction with p-toluidine and sodium periodate Original Research Article

A new spectrophotometric flow injection method has been established for the determination of some catecholamine drugs (methyl dopa I, dopamine.HCl II and adrenaline III). The method is based on the oxidative coupling reaction of catecholamine with p-toluidine and sodium periodate to form an orange water-soluble dye product that has a maximum absorption at 480 nm. Linearity was observed in the range of 1–50, 2–50 and 5–70, with a limit of detection (S/N = 3) of 0.4, 0.2 and 0.7 μg ml−1 for I–III, respectively. The method was applied successfully to the determination of I–III in pharmaceutical preparations with a good precision and accuracy.