Analytical study for the charge-Transfer complexes of gabapentin

Abstract

Studies were carried out, for the first time, to investigate the charge-transfer reactions ofgabapentin as n-electron donor with the σ-acceptor: iodine and various π-acceptors: 7,7,8,8-tetracyanoquino-dimethane (TCNQ), 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), 2,5-dichloro-3,6-dihydroxy-1,4-benzoquinone (chloranilic acid, pCA), tetracyanoethylene (TCNE) and 2,3,5,6-tetrachloro-1,4-benzoquinone (chloranil). Different colored charge-transfer complexes and radical anions were obtained. Different variables affecting the reactions were studied and optimized. The formations of the colored complexes were utilized in the development of simple, rapid and accurate spectrophotometric methods for the analysis ofgabapentin in pure form as well as in its pharmaceutical preparation. Under the optimum reaction conditions, linear relationships with good correlation coefficients (0.9995 - 0.9999) were found between the absorbance and the concentrations of gabapentin in the range of 6.0 - 200 µg ml-1. The limits of assays detection ranged from 0.39 to 7.59 µg ml-1. No interference could be observed from the additives commonly present in the pharmaceutical preparation. The methods were success-fully applied to the analysis of pharmaceutical preparation that contain gabapentin, with good accuracy and precision; the percentages recovery ± S.D. ranged from 99.29 ± 0.651 to 100.36 ± 1.56. The results were compared favorably with the reported method. Key words: Charge-transfer complexes, gabapentin, pharmaceutical analysis, spectrophotometry.