The UV–vis absorption spectrum of caffeine in water is
found to be in the region of 243–302 nm at room temperature.
It is clearly shown in Fig. 1 that the spectral intensity
of caffeine drops to zero at wavelength greater than
302 nm, on the other hand a new peak absorbance is
noticed at a wavelength below 243 nm. This new spectrum
is expected to be the peak absorbance due to the solvent.
The peak absorbance of the solution is found to be
A = 1.224 at the maximum wavelength kmax ¼ 272 nm.
The maximum peak absorbance for caffeine observed in
these experiments was quite similar to those reported by
Clarke and Macrae (1985). The molar decadic absorption
coefficient measuring the intensity of optical absorption
at a given wavelength was calculated using Beer–Lambert’s
equation (Liptay, 1969). The molar decadic absorption
coefficient of caffeine in water is computed and value of
emax = 1115 m2 mol1 is obtained. The transitional dipole
moment of the dissolved molecule, which is related to the
molar decadic absorption coefficient by the integral