The volatile oils are complex mixture systems. The IR spectra
show a total overlap of each absorption spectrum of various components.
The IR characteristic fingerprint peaks for the cinnamon
samples are mostly in the range of 1800–600 cm−1 (Fig. 3a and b).
The typical spectra in Fig. 3a of cinnamons were analyzed and several
characters can be extracted, such as the peak at 1727 cm−1,
corresponding to the aldehyde of a saturated fat, and the peaks
at 1679 cm−1 and 1626 cm−1, which correspond to the stretching
vibration of an aldehyde carbonyl C O. These main peaks correspond
to high levels of cinnamaldehyde and aldehydes in the
volatile oil of cinnamon bark. The peak at 1573 cm−1 is assigned to
the aromatic ring C C skeleton vibration of an aromatic substance.
The peak at 1450 cm−1 is very characteristic for an alcohol C OH
within the bending vibration absorption. The peak at 1294 cm−1
is attributed to the CH2 alkanes that face the swing and the aromatic
ring C H for the in-plane bending absorption, and the peak
at 1248 cm−1 corresponds to the aromatic acid ester C O C symmetric
expansion and the stretching vibration of the phenolic C OH
groups, which displays the characteristic absorptions of esters and
eugenol in volatile oil. The peaks at 1124 cm−1 and 1070 cm−1
are attributed to the stretching vibrations of C O and the C OH
deformation vibration. The peak at 973 cm−1 is assigned to the
C H bending vibration absorption, and the peak at 748 cm−1 is
assigned to benzene rings CH vibration absorption. The peak at
685 cm−1 corresponds to the vibration absorption of alkenes. The
volatile oil compounds exhibit much complexity and diversity, as
shown in Fig. 3b. However, the spectra for all of the samples in
the range of 1800–600 cm−1 are quite similar. The 16 common
peaks were observed in all the IR spectra of the 9 studied cinnamon
samples. Because the chemical composition fingerprints have high