Validated spectral manipulations for determination of an anti-neoplastic drug and its related impurities including its hazardous degradation product.

Innovative and specific double dual wavelength, dual ratio subtraction spectrophotometric methods were carried out along with a successive ratio subtraction spectrophotometric method for determination of dacarbazine and its related impurities including toxic and hazardous ones. For determination of dacarbazine by the double dual wavelength method, the absorbance differences between 323 and 350 nm of the zero order absorption spectra of dacarbazine were used. The values of absorbance difference between 267.2 and 286.2 nm of the zero order spectra of 5-amino-imidazole-4 carboxamide were used for its determination by the dual ratio subtraction method. The zero order absorption spectrum of 2-azahypoxanthine at 235 nm was used for its determination after applying the successive ratio subtraction method. ICH guidelines were followed for validation of the developed methods, where linear relationships were obtained in the range of 4-20, 1-16, and 2-20 μg mL for dacarbazine, 5-amino imidazole-4-carboxamide and 2-azahypoxanthine, respectively. Accurate, precise, and specific results were obtained upon applying the proposed methods according to ICH guidelines. Furthermore, the developed methods were successfully applied for determination of dacarbazine in its pharmaceutical formulation. Comparing the results of the developed methods with those of the official USP spectrophotometric method statistically showed no significant difference. The developed methods don't need any sophisticated techniques so they are considered cost effective methods. Moreover, the introduced methods have the advantages of being green where water was used as a solvent. The methods proved to be more economic, fast and simple than other reported HPLC methods.