Abstract
Diphenhydramine HClis a weakly fluorescent drug having tertiary amine group forming ion pair complex with eosin Y in dichloromethane at pH 5 in disodium hydrogen phosphate-citric acid buffer solution. The complex formation was the basis for the development of new analytical method for determination of active diphenhydramine in pharmaceutical formulations. The stoichiometric ratio between diphenhydramine and eosin Y was studied by mole ratio method and found to be 2:1. The ion-pair complex showed maximum fluorescence emission intensity at 554 nm with excitation at 259 nm. The linear dynamic range was obtained in the concentration range of 2-22 µg mL-1 with a linear equation of FI = 0.361 + 13.675 C. The apparent Gibb’s free energy (ΔGº) was calculated and found to be -80.783 KJ mol-1, confirmed the feasibility of the reaction. The proposed method was successfully applied to the determination of diphenhydramine HCl in pharmaceutical formulations and in good agreement with the reference method.
Highlights
Diphenhydramine hydrochloride is chemically known as 2-(Diphenylmethoxy)-N,N-dimethylethylamine hydrochloride (CAS: 147-24-0; M.W.: 291.82)
The assay of diphenhydramine hydrochloride is described in British Pharmacopoeia [2], United States Pharmacopeia [3] and Indian Pharmacopoeia [4] based on potentiometric titration, high performance liquid chromatographic method and volumetric titration, respectively
Eosin Y acted as a fluorescent probe and formed fluorescent ion-pair complex with diphenhydramine in the presence of disodium hydrogen phosphate-citric acid buffer solution of pH 5.0
Summary
Diphenhydramine hydrochloride is chemically known as 2-(Diphenylmethoxy)-N,N-dimethylethylamine hydrochloride (CAS: 147-24-0; M.W.: 291.82). The complex was extracted in dichloromethane provided fluorescence emission intensity at 554 nm after excitation at 259 nm. The fluorescence emission intensity of the associated ion pair complex in organic layer was recorded at 554 nm after excitation at 259 nm and the linear regression equation was developed for the estimation of active diphenhydramine in pharmaceutical formulations.
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