Thermal stability studies of 5‐fluorouracil using diffuse reflectance infrared spectroscopy

5‐Fluorouracil is one of the oldest chemotherapy drugs and it has been in use for decades. It is an active medicine against several types of cancer and effectively blocks the replication of DNA viruses. The present study assessed the potential of diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy to determine the thermal stability of 5‐fluorouracil. Infrared spectra of the drug before and after exposure to thermal radiation at different temperatures were collected in diffuse reflectance mode using a Fourier transform infrared (FTIR) spectrophotometer. Differential scanning calorimetry (DSC) and X‐ray diffraction (XRD) analysis were carried out simultaneously to confirm and support the results of infrared spectroscopy. The DRIFT spectra reveal that the drug shows good thermal stability up to 275 °C and undergoes complete thermal breakdown at about 285 °C. The results of DSC and XRD analysis also give the same information, which support the implementation of diffuse reflectance infrared spectroscopy for the determination of thermal stability of 5‐fluorouracil. Copyright © 2009 John Wiley & Sons, Ltd.