Transmission FTIR derivative spectroscopy for estimation of furosemide in raw material and tablet dosage form

A Fourier transform infrared derivative spectroscopy (FTIR-DS) method has been developed for determining furosemide (FUR) in pharmaceutical solid dosage form. The method involves the extraction of FUR from tablets with N,N-dimethylformamide by sonication and direct measurement in liquid phase mode using a reduced path length cell. In general, the spectra were measured in transmission mode and the equipment was configured to collect a spectrum at 4 cm(−1) resolution and a 13 s collection time (10 scans co-added). The spectra were collected between 1400 cm(−1) and 450 cm(−1). Derivative spectroscopy was used for data processing and quantitative measurement using the peak area of the second order spectrum of the major spectral band found at 1165 cm(−1) (SO(2) stretching of FUR) with baseline correction. The method fulfilled most validation requirements in the 2 mg/mL and 20 mg/mL range, with a 0.9998 coefficient of determination obtained by simple calibration model, and a general coefficient of variation <2%. The mean recovery for the proposed assay method resulted within the (100±3)% over the 80%–120% range of the target concentration. The results agree with a pharmacopoeial method and, therefore, could be considered interchangeable.