Abstract

The integrated absorption cross-section of caffeine in water and dichloromethane, in the wave number regions of  20,000 – 39,062 cm^-1 at room temperature, were  (4.44 ± 0.18) × 10⁷ and  (4.32 ± 0.11) × 10⁷  L mol^-1 cm^-2, respectively. The corresponding calculated values for oscillator strength of caffeine in water and dichloromethane were 0.19 × 0.01 and 0.18 ± 0.01, respectively. In addition, the number densities of caffeine in different coffee beans were reported using integrated absorption coefficient technique. The number density of caffeine calculated in different coffee varieties were (3.53 – 4.76) × 10^-5 mol L^-1. The new applied technique has an advantage over other techniques in that it provides more information about the nature of the absorbing molecules and establishes accurate evaluation of the UV-Vis absorption intensity.

Key words: Caffeine, number density, integrated absorption coefficient, integrated absorption cross-section, oscillator strength.