Flow-Injection Spectrophotometric Determination of Methimazole in Pharmaceuticals Using a Charge Transfer Complex Cu(I)‒Neocuproine

In this work an accurate, fast and high throughput flow procedure was developed in order to determine methimazole in pharmaceutical formulations. The method is based on reduction of Cu(II) to Cu(I) by methimazole in the presence of 2,9-dimethyl-1,10-phenanthroline (neocuproine), followed by the generating a yellow charge-transfer complex that was spectrophotometrically monitored at 455 nm. The methimazole analytical curve was linear in a concentration range from 4.0 × 10^–5 to 1.5 × 10^–4 M. The sample throughput was 90 h^–1 and the relative standard deviation was 0.3% for a methimazole solution. The average recovery was 99%. The developed method is economic due to reduced consumption of samples and reagents. Samples can be analyzed without special pretreatment or using of organic solvents.