Colorimetric Determination of Stability Constant of Acetaminophen-Cu(II) complex by Classical Equation Depending on Stoichiometric Curves


  • O. V. Ikpeazu Abia State University, Uturu, Abia State, Nigeria
  • Ifeanyi E. Otuokere Michael Okpara University of Agriculture, Umudike, Abia State,Nigeria
  • K. K. Igwe Michael Okpara University of Agriculture Umudike, , Abia State Nigeria


Acetaminophen, copper, complex, stability constant


Communication in Physical Sciences 2020, 5(3): 371-377

Authors: V. Ikpeazu, I. E. Otuokere and K. K. Igwe

Received 15 April 2020/Accepted 28 June 2020

Acetaminophen is a nonsteroidal anti-inflammatory drug (NSAID) that is used for the treatment of pain, fever and headache. Classical equation has been used in the calculation of stability constant of acetaminophen-Cu(II) complex depending on the theoretical explanation of the stoichiometry, continuous variation and mole ratio methods.The formation of Cu(II) complex with acetaminophen was studied colorimetrically at an absorption maximum of 630 nm at 25 and 40 oC. The data showed that Cu(II) and acetaminophen combine in the molar ratio of 1:1  at pH 7.4 with ionic strength maintained using 0.1M KNO3. Calculated stability constants values were 1.18 x 102 and 1.11 x 102 using continuous variation method and 1.25 x 102 and 1.11 x 102 using mole ratio methods at 25 and 40 oC respectively. Calculated ∆GƟ for the complex were - 1.18 x 104 and-1.23 x 104 J using continuous variation method and - 1.20 x 104 J and -1.23 x 104 J using mole ratio method at 25 and 40 oC respectively. The stoichiometry, stability constant and Gibbs free energy results suggested that acetaminophen used in the study is a good chelating agent and can be an efficient antidote in the therapy of Cu(II) overload or poisoning


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Author Biographies

O. V. Ikpeazu, Abia State University, Uturu, Abia State, Nigeria

Department of Biochemistry

Ifeanyi E. Otuokere, Michael Okpara University of Agriculture, Umudike, Abia State,Nigeria

Department of Chemistry


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