Quality control Fourier transform infrared determination of diazepam in pharmaceuticals

A quality control procedure has been developed for the determination of diazepam in pharmaceuticals using Fourier transform infrared (FTIR) spectroscopy. The method involves the off-line extraction of diazepam with chloroform by sonication and direct determination in the extracts through peak area measurement in the interval between 1672 and 1682 cm−1 using a baseline correction defined between 1850 and 1524 cm−1. For standardization it was used an external calibration line established from standard solutions of diazepam in chloroform. The method provides a limit of detection of 0.04 mg per tablet (n = 5), a relative standard deviation (R.S.D.) of 0.5% for 5 independent measurements of a standard solution at a concentration level of 0.76 mg g−1 and a sampling frequency of the whole procedure of 4 h−1, being required only 45 s for the measurement step. Results obtained by FTIR agree with those obtained by a reference methodology based on ultraviolet spectrometry and thus the developed procedure offers a good alternative for the determination of diazepam in pharmaceuticals.