Determination of some catecholamines based on their reaction with periodate

An indirect kinetic-spectrophotometric method is proposed for the determination of trace amounts of levodopa, methyldopa, dopamine, and adrenaline based on their reaction with periodate in acidic media. The excess periodate that is related to the amount of catecholamines is determined by its reaction with iodide in the presence of methylene blue. The reaction is monitored spectrophotometrically by measuring the decrease in the absorbance of the solution at 665 nm with a fixed time method of 3.0 min. The relative standard deviation for seven replicate determinations of 0.5 mugmL(-1) of L-dopa, methyldopa, dopamine and adrenaline was 1.80, 1.20, 0.92 and 1.35%, respectively. The method was successfully applied to the determination of catecholamines in pure form and in pharmaceutical preparations.