Determination of integrated absorption cross-section, oscillator strength and number density of caffeine in coffee beans by the integrated absorption coefficient technique.

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.