The extraction techniques could not completely remove
the possible interferences with caffeine spectra. Therefore,
extracting qualitative and quantitative information from
the spectra composed of unresolved bands is impossible.
The interfering bands were observed at wavelength
308 nm as shown in Fig. 8. From the literature report the
compounds that absorbed in these regions are belong to
chlorogenic acid related compounds (p-coumaroyquinic
acid) (Martin, 1970; Clarke et al., 1985). It has been
reported that the chlorogenic acid makes complexes with
Caffeine. To eliminate these interference spectra Gaussian
fit was applied. It is assumed that the line shape of interferences
spectra has a Gaussian function. Fig. 7 shows the
spectra of caffeine in coffee seeds extracted by dichloromethane
before Gaussian fit while Fig. 8 shows the spectra
of caffeine with Gaussian fit and Fig. 9 the spectra of caffeine
after the best Gaussian fit is subtracted. As it is seen
in Fig. 9, the line shape of the spectra after Gaussian fit is
subtracted exactly similar to the shape of spectra of the
pure caffeine dissolved in dichloromethane.
Further to compare this spectra with pure caffeine the
two spectra were overlapped. Fig. 10 shows the normalized