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

Integrated absorption cross-section and oscillator strength of caffeine in water and dichloromethane were reported by UV-Vis spectrometer in the wave number regions of 20,000-39,062 cm(-1) at room temperature. The integrated absorption cross-section of caffeine in water and dichloromethane in these wave number regions were (4.44 +/- 0.18) x 10(7) and (4.32 +/- 0.11) x 10(7) L mol(-1) cm(-2), respectively. The corresponding calculated value for oscillator strength of caffeine in water and dichloromethane were 0.19 +/- 0.01 and 0.18 +/- 0.01, respectively. In addition number densities of caffeine in different coffee beans were reported using integrating absorption coefficient technique. The calculated number density of caffeine for different coffee varieties were varying from (3.53-4.76) x 10(-5) mol L(-1). The new applied technique has an advantage over other techniques in that it provides additional information about the nature of the absorbing molecules and establishes accurate evaluation of the UV-Vis absorption intensity. (C) 2009 Elsevier Ltd. All rights reserved.