FT-MIR analysis
FT-MIR spectra of samples were obtained using Nicolet 6700
FTIR spectrometer (Thermo Nicolet Corp., Madison, WI) with HATR
crystal of ZnSe 45 equipped with deuterated triglycine sulphate
(DTGS) as detector, potassium bromide (KBr) as beam splitter
and controlled with the Omnic Software (Version 7.0 Thermo Nicolet).
The measurements were directly carried out by putting oil
samples on HATR surface at controlled room temperature (20 C)
in MIR region of 4000–650 cm1
, by accumulating 32 scans with
the resolution of 4 cm1
. These spectra were subtracted from reference
spectrum of air, acquired by collecting a spectrum from the
cl cleaned blank HATR crystal before the measurement of each oil
sample replication. The sample spectra were collected in triplicate
and displayed as the average spectra. At the end of every scan, the
surface of HATR crystal was cleaned with hexane twice and dried
with special soft tissue, cleaned with acetone, and finally dried
with soft tissue following the collection of each spectrum.