Spectrophotometric determination of the methyldopa and levodopa through oxidative coupling reactions using the prepared reagent [2-amino-5-(para-aminophenyl)-1,3,4-oxadiazole],Mosul, Iraq

This study involved the spectrometric determination of primary amine-containing pharmaceutical compounds. 2-amino-5-(para-aminophenyl)-1,3,4-oxadiazole was synthesized and used as a reagent for the analysis of the pharmaceutical compound's methyl-dopa and levodopa using the oxidative coupling method. The UV-spectra for methyl-dopa and levodopa give light brown and brown color in solution after treatment with oxidizing agents with λMax of 404 nm and 417 nm respectively. The optimal concentrations determined with the best reagent volume of 0.75 mL for methyl-dopa and 1.0 mL for levodopa was 40 µg/mL and 30 µg/mL, respectively. Moreover, Potassium dichromate was found to be the most effective oxidizing agent. In addition, the limit of detection (LOD) obtained for both drugs was1.021 µg/mL and 4.125 µg/mL, while the limit of quantitation (LOQ) obtained was 2.762 µg/mL and 8.143 µg/mL, respectively. The average percentage recovery for each drug was almost 99.663 and 100.06%, with relative standard deviations of (1.357, 1.246) %, respectively. The developed method was applied to pharmaceutical preparations with accuracy and high precision.