FT-IR Spectroscopy Applied for Identification of a Mineral Drug Substance in Drug Products: Application to Bentonite

Table 2

IR bands characteristic of the purified bentonite spectrum.

Transmission vibrational frequency (cm^−1)	Strength	Functional groups
3632	Medium	OH stretching
3437	Medium	H2O stretching
1638	Weak	H2O bending
1042	Broad	Si-O stretching
915	Broad	Al-OH-Al bending
884	Medium	Al-OH-Fe bending
842	Medium	Al-OH-Mg bending
795	Weak	Si-O stretching of quartz and silica
622	Weak	Al-O + Si-O out-of-plane vibration
522	Broad	Al-O-Si bending