Extractive spectrophotometric determination of α-methyldopa in bulk dosage and in its formulations

A simple, sensitive, extractive spectrophotometric method for determination of α-methyldopa in both pure form and in pharmaceutical formulations is described. The method is based on the reaction of diazotized p-aminoacetophenone with α-methyldopa in basic medium to yield an orange-yellow-coloured product having an absorption maximum at 440 nm. The orange-coloured species was extracted in isopentanol. The coloured species obeyed Beer’s law in the range of 0.05–0.5 µg/mL. The molar absorptivity as obtained from Beer’s law data was found to be 0.3736 × 106 L mol−1 cm−1, while Sandell’s sensitivity was found to be 0.00064 µg cm−2. Common excipients did not interfere with the proposed method. The result obtained by the proposed method compares favorably with other reported methods. The proposed method offers the advantages of simplicity and higher sensitivity over the other existing methods.