An Effective Application of the Spectrophotometric and Thermodynamic Methods for the Determination of Thiamine Hydrochloride

An effective application of the spectrophotometric and thermodynamic methods have been described
for the determination of thiamine hydrochloride. The spectrophotometric method was based on charge
transfer complexation reaction using thiamine as n-electron donor and 2, 3 dichloro-5,6-dicyano -1,4-
benzoquinone (DDQ) as a π-acceptor to form a highly coloured species with 1:1 stoichiometric ratio.
The coloured product was quantified spectrometrically at 474nm under the established experimental
conditions. Beer’s law was obeyed over the concentration ranges of 5-80μg/ml. The Apparent molar
absorptivity was calculated to be 1.08 x 103Lmol-1cm-1 with the corresponding Sandell sensitivity of
2.68. The Ross equation was used for studying the thermodynamic parameters and result reveals that
ΔS was calculated to be between 67.13J/mol and 66.70J/mol , ΔH = -2.87kJ/mol. The association
constants were found to decrease from 30°C to 60°C with increase in molar absorptivity. Also high
values of association constant were seen which ranged from 500Lmol-1cm-1 to 1667Lmol-1cm-1. The
proposed methods were applied successfully to the determination of thiamine hydrochloride in pure
and commercial forms with average recovery of 96.2% ± 0.016. Statistical comparison of the results
were performed using student’s t-test and f-test at 95% confidence level.