• Wallada H. Ibrahim Department of Pharmaceutical Chemistry, College of Pharmacy, University of Mosul, Mosul, Iraq
  • Hana Sh. Mahmood Department of Chemistry, College of Science, University of Mosul, Mosul, Iraq



Captopril, Atenolol, Metoprolol, neutral red, bleaching reaction


Three antihypertensive drugs Captopril (CPL), Atenolol (ATL), and Metoprolol (MTL) have been estimated sensitively and selectively by a single spectrophotometric method using neutral red dye NLR. The method is based on oxidation of the drugs by known excess of N-bromosuccinamide (NBS) in the first reaction step followed by the oxidation of NLR dye with the exceed ed amount of NBS, as the concentration of the drug compounds increase, the color of the dye increase, the dye exhibits absorbance peak at 523 nm. The linearity range was from 1 to 10 µg/ml for the three drugs, the molar absorptivity values were 2.1164 × 105, 1.9202× 104, and 57.934× 104 for CPL, ATL, and MTL respectively, the sensitivity index of Sand’ll were 0.0102, 0.0138, and 0.01182 µg/cm2 for CPL, ATL, and MTL respectively. LOD values for the three drugs ranged from 0.00405 to 0.00547 and LOQ values were ranged from 0.0135 to 0.0182 respectively, the method exhibits good applicability to the dosage forms and high confidence as compared with standard method and standard addition method.


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