DETERMINATION OF CAFFEINE IN SOLID PHARMACEUTICAL SAMPLES BY FTIR SPECTROSCOPY

Fourier transform infrared spectroscopy has been used for the quantita tive determination of caffeine in several pharmaceutical products: ace tyl salicylic acid, paracetamol and propyphenazone. The method is simp le, rapid and selective, and allows the determination of caffeine with out sample pretreatment and without separation from the matrix. Two te chniques for measuring the infrared spectra of caffeine are described: transmission through pellets and diffuse reflectance from powder (DRI FT). In both methods, samples were diluted (1%) with KBr. Caffeine in pharmaceutical matrices was recovered within 5% error in pellets and 1 0% by DRIFT. Relative standard deviations were generally less-than-or- equal-to 1.5% for repeated measurements on a single pellet and less-th an-or-equal-to 5% for measurements on different pellets. DRIFT in the vacuum mode gave rather large RSDs. The limit of detection of the pell et technique was about 0.5% caffeine in the original sample.