Chemistry Reference
In-Depth Information
Table 21.3
Amide I and II related IR signals.
Spectral Region (cm
−1
)
Functional Group Vibration
Amide
1690-1665
C
=
O stretching
I
1670-1640
N-H bending
I
1665-1630
C-N stretching
I
1590-1565
C-N stretching
II
1575-1550
N-H bending
II
Table 21.4
Nucleic acid IR signals.
Spectral Region (cm
−1
)
Functional Group Vibration
1705-1660
C
=
O stretching
1625-1600
C
=
C stretching
1605-1575
N stretching
1265-1220 PO
2
−
asymmetric stretching
1160-1120 C-O stretching
1105-1080 PO
2
−
asymmetric stretching
1065-1000 C-O stretching
C
=
the case of nucleic acids the asymmetric and symmetric phosphate stretching, and in-plane double-bond
vibrations of bases have been reported as the most important IR spectral features. Some of the mid-IR signals
are shown in Table 21.4.
Although all the above discussions about the capabilities of IR spectroscopy in analysis of bio-active
chemical are really useful and interesting, there is a fact which concerns us about our goals and path. Almost
all the clinical and medicine related bio-samples to be analyzed by IR spectroscopy are a combination of
these chemicals and it is nearly impossible to separate and analyze them singularly. Thus we need to define
some strategies which could enable the analyst to conduct a diagnostic process, taking into account all the
probable variations in any of the chemical ingredients in bio-samples. When a medicine researcher decides to
analyze a bio-fluid, such as blood, by IR spectroscopy, it is impossible to provide a separation system which
can perform the quantitative analysis of sugar apart from other constituents which will probably cause some
interference. Thus we need to discuss the capabilities of IR spectroscopy in case of complex samples.
Application of IR spectroscopy for analysis of single analytes in body fluids and IR spectral pattern recognition
are the introductions to this subject.
21.3
Medical analysis of body fluids by infrared spectroscopy
IR spectroscopy is very useful for clinical investigative analysis of bio-fluids according to its advantages
which were discussed during the introduction of this chapter. The main procedure in a biodiagnostic route is
to record the IR spectrum of the body bio-fluid sample, converting the spectral data to interpretable medical
information and finally making a medical decision. The common mandatory steps are:
1) To remove the data which are not reliable due to the serious deviations from the other data which is called
'outlier detection' and to build a model of calibration, consisting of spectra from samples with known
characteristics. The aim is to obtain a logical correlation between the spectral data and the object of the
