Indirect spectrophotometric determination of folic acid based on the oxidation reaction and studying some of the thermodynamic parameters

Indirect spectrophotometric determination of folic acid based on the oxidation reaction and studying some of the thermodynamic parameters

Nabeel S. Othman1, Shlear H. Hasan2 & Kafia M. Surchi3

1 Chemistry Department, College of Science, Mosul University, Mosul, Iraq.

2 Department of food technology, College of Agriculture, University of Salahaddin, Erbil, Iraq.

3 Chemistry Department, College of Science, University of Salahaddin, Erbil, Iraq.

E-mail: blndmuh@yahoo.co.uk






Article info
Original: 02 Oct. 2014
Revised: 14 Nov. 2014
Accepted: 10 Dec. 2015
Published online:  
             20 March  2015

Key Words:
Spectrophotometry
Folic acid
2,2'-Bipyridyl/FeCl3
Thermodynamic
parameters 


Abstract

A simple and sensitive indirect spectrophotometric method was developed for the determination of folic acid in pure form and in its pharmaceutical formulations. The method was based on the oxidation of folic acid by iron (III) in acidic medium, then reaction of liberated iron (II) with 2, 2'-bipyridyl to produce a red complex which is water-soluble, stable, and has a maximum absorption at 520 nm against the reagent blank with a molar absorptivity of 2.8338 x 105 L .mol-1.cm-1. Beer’s law is valid over the concentration range of 0.5-18.0 µg/ml folic acid. The values of some thermodynamic parameters [free energy change (ΔG), enthalpy change (ΔH), and entropy change (ΔS)] were estimated from the values of stability constants (K) at different temperatures .It was found  that  colored product formation was spontaneous, exothermic and accompanied by an increase of random. The proposed method has been applied successfully to determine folic acid in different pharmaceutical preparations.

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