Fourier transform infrared spectrometry (FTIR) for qualitative and quantitative analysis of azodicarboxamide and its potential impurities

Azodicarboxamide was determined by Fourier Transform Infrared (FTIR) attenuated total reflectance spectrophotometry (FTIR-ATR) in dimethyl sulfoxide (DMSO) solutions. Validation of the method was made as well on the raw material and on dosage forms (capsules). The linear range for azodicarboxamide determination was from 10 to 40 mg ml−1 with a correlation coefficient of 0.9998 (n=15). The presence of flowing agents in the dosage form did not impair the results. The detection and quantitation of impurities in azodicarboxamide (diethylazodicarboxylate, 1,2-dicarbethoxyhydrazine and ethyl formate), which are residual by-products coming from the drug synthesis was performed by transmission FTIR spectrometry in C2Cl4 and CHCl3 solutions. These impurities contain an ester function which make them soluble in non polar solvents unlike azodicarboxamide. The linear ranges for the determination of these impurities were validated from 0 to 1000 μg ml−1 with linear correlation coefficients >0.9994 (n=18). Impurities may be detected down to 5.0 μg g−1 and quantified down to 15 μg g−1.