Spectrophotometric Determination of Amlodipine Besylate in Pure Forms and Tablets

ABSTRACT

Two simple and sensitive spectrophotometric methods for the determination of amlodipine besylate (ADB) in pure forms and tablets are described. These methods are based on the formation of an ion association complex between the drug and an acidic dye, Bromothymol blue, which is extractable into chloroform and has an absorption maximum at 405nm (Method-A), or by the formation of an oxidative coupling product with 3-methyl-2-benzothiazolinone hydrazone hydrochloride (MBTH) in the presence of ceric ammonium sulphate (absorption maximum at 630nm (Method-B)). Beer's Law limits for Methods A and B are 5 to 40 μg/ml. All variables in these methods are optimised and the reaction mechanisms are presented. No interferences were observed from tablet additives and the applicability of the methods was examined by analysing tablets containing ADB. The quantities determined were 99.5–100.2% of the expected value.

KEY WORDS:

• Visible spectophotometry
• amlodipine besylate
• 3-methyl-2-benzothiazolinone hydrazone hydrochloride
• bromothymol blue
• ion association complex
• oxidative coupling