2. INTRODUCTION
Infra-red spectrum is an important record which
gives sufficient information about the structure of a
compound.
In recent years, NIR spectroscopy
has become so widespread in process analysis and
within pharmaceutical industry for raw material
testing, pharmaceutical industry in biotechnology,
genomics analysis, proteomic analysis ,textile monitoring,
food analysis, plastics, textiles, insect detection forensic lab
application, crime detection, various military applications,
4. HISTORY
The history of NIR is begins with William
Herschel in18th century. He found the radiant heat beyond the
red end while using large glass prism to disperse the sunlight
onto the three thermometers having carbon blackened bulbs.
The heat is known as “NIR radiation” and the spectrum as
“NIR Spectrum”
5. THEORY AND PRINCIPLE
Near-IR (NIR) is a spectroscopic method is based on
molecular overtones and combination vibrations of C-H,
O-H and N-H
Combinations arise by interaction of two or more vibrations
taking place simultaneously.
For a given molecule, a normal mode of vibration corresponds
to internal atomic motions in which all atoms move in phase
with same frequency but with different amplitude.
Additionally to these normal vibrations transitions corresponds
to be called overtones. Such transitions are forbidden by the
selection rules of quantum mechanics. As a result the molar
absorptivity in the near IR region is very small.
6. HOOKE’S LAW
C = speed of light,(2.998 × 1010 )gm sec-2
K = force constant (5 × 105 dynes/cm).
m1 m2 = masses of atom concerned in grams in a perticular bond
7. o Hooke’s law can be used to calculate the fundamental
vibrations for diatomic molecules in IR.
o Transition from the ground state to the first excited
state absorbs light strongly in IR region and give rise
to intense bands called the fundamental bands.
o Transition from the ground state to the second excited
state with the absorption of NIR give rise to weak
bands called 1st overtone in NIR.
o Transition from the ground state to the third excited state
with the absorption of NIR give rise to weak bands called
2st overtone in NIR.
o Like wise 3rd and 4th overtone bands
will occur based on the transition to the fourth and
fifth excited state with the absorption of NIR.
8.
NIR is comprised of combinations and overtones that is
anharmonic oscillation.
Most molecules contain covalent bonds which share
electrons between atoms. Although bonds are elastic,
they do not obey Hooke’s law exactly. The model of
anharmonic oscillation is more precise.
Harmonic oscillator can not be retained at larger
amplitudes of vibrations owing to repulsive forces
between the vibrating atoms and possibility of
dissociation..
10. FRANCK-CONDON PRINCIPLE
The Franck-Condon
Principle states that as
electrons move very much
faster than nuclei, the nuclei
as effectively stationary
during an electronic
transition.
In the ground state, the
molecule is most likely in v=0.
11. The most likely place to
find an oscillating object
is at its turning point
(where it slows down and
reverses). So the most
likely transition is to a
turning point on the
excited state.
The electron excitation is
effectively instantaneous;
the nuclei do not have a
chance to move. The
transition is represented
by a VERTICAL ARROW
on the diagram (R does
not change).
12. QUANTUM (MATHEMATICAL) DESCRIPTION OF
FC PRINCIPLE
approximately
constant with
geometry
Franck-Condon (FC)
factor
If electronic excitation is much faster than nuclei move,
then wave function cannot change. The most likely
transition is the one that has most overlap with the
excited state wave function.
14. BASIC CONFIGURATIONS OF NIR
Conf B has to be used for multichannel spectroscopy
because a wide range spectrum is being simultaneously
measured with a multichannel detector.
Conf A is commonly preferred. In the case of
interference-filter spectroscopy, it is better because
unnecessary components of the light are cut off before
the sample position.
15.
16. LIGHT SOURCES
1.LIGHT EMITTING DIODES(LED)
Gallium arsenide
Advantages: they require low power
have Long life expectancy.
2. TUNGSTEN LAMPS (incandescent bulbs)
produce heat up to 1100k.
Advantages
cheap
readily available
17. 2) MONOCHROMATOR:
1.
2.
Two typs of monochromator used
Prism
Grating
Grating monochromator is used to measure the full
visible and NIR spectrum may be in transmittance
or reflectance
It is mainly used for research or when a wide range
of different applications is required.
18. SAMPLES PRESENTAION
Transmittance: calculated by dividing the radiant power of
the light transmitted through the sample by the radiant power
of the incident light
Reflectance: calculated using the ratio of the radiant power of
reflected light to the radiant power of incident light
Transflectance: calculated by dividing the radiant power of
light that has traversed a sample twice (once right after it was
emitted, and once after if was reflected by a reflector) by the
radiant power of the incident light
19. DETECTOR
The choice of detectors depends on
Wavelength range,
Spectrometer design characterstics
detector characteristics such as photosensitivity
(responsivity),noise equivalent power (NEP),etc
Detectors using in NIR spectrometers are
1. Lead sulphide detectos (PbS),
2. Lead selenide detectors (PbSe),
3. Silicon detectors,
4. Indium antimonide detectors,
5. InGaAs, InSb, Common Charged Coupled Devices
(CCD).
21. CLASSIFICATION OF MODERN NIR
INSTRUMENTS
Filter based instruments
AOTF based instruments
Scaning grating based instruments
Fourier-transform based instruments
Multichannel Fourier-transform (MCFT)
spectroscopy
22. FILTER-BASED INSTRUMENTS
A filter allows a particular portion of the spectrum to
pass through or blocks all wavelengths below or above a
certain frequency. An interference filter consists of a
transparent dielectric spacing material separating two
partially reflective windows, allowing a specific set of
wavelengths to pass..
source
Interference filter
sample
detector
23. ACOUSTIC OPTICAL TUNEABLE FILTER
In AOTF wavelength selectors light is directed into a
crystal of TeO2 . A high-frequency acoustic wave in the
radio frequency range is coupled into the crystal by the
use of a piezoelectric material bonded to the crystal.
These acoustic waves quickly propagate through the
crystal, interact with the broadband light and generate
two monochromatic beams of light, each polarized in a
different direction.
it has no moving
parts, adjustable
intensity and
gives narrow
beams
24. TILTING FILTER
It’s first type of interference filter. The transmitted
energy at various wavelength depends on the incident
angle of light passing through the filter. In this, the filters
were mounted in an encoder wheel for greater accuracy
i.e. wavelength reproducibility.
25. FOURIER TRANSFORM -BASED INSTRUMENTS
The interferometer works on the principle whereby light from the
source is split into two segments by the beam-splitter.
One portion travels to a fixed mirror and is reflected back to the
splitter and The second portion strikes on a moving mirror and
returns to be recombined with the first portion of light.
It’s pattern of peaks/troughs is called an interferogram and by
applying mathematical calculations to these, a spectrum evolves.
Interferometers are popular in both mid-range infrared and NIR.
26. MULTICHANNEL FOURIER-TRANSFORM
(MCFT) SPECTROSCOPY
This instrument utilizes a fixed monochromator, usually
a holographic grating and an array of many small
detectors. The light is collimated onto the grating and is
thereafter dispersed into component wavelengths. The
wavelengths are then directed to a series of photo-diodes.
Photo-diode arrays are more commonly used for process
control.
Fixed monochromator
source sample
slit
detector
28.
1.
2.
3.
1.
2.
3.
4.
1.
2.
3.
4.
5.
6.
7.
Identification and qualification of raw materials and intermediates.
Library approach .
Conformity approach
Quantitative calibration models
Analysis of intact dosage forms
Tablets.
Capsules
Lyophilized products
Polymeric implants and microspheres.
Process monitoring and process control
Powder blending
Drying
Granulation .
Pelletization
Tabletting and capsule-filling
Film coating
Packaging
29. NIR AGRICULTURAL APPLICATIONS
it is in commercial use in Japan, primarily for melons and citrus
fruit.
The technology may be used to exclude fruit with internal
defects.
A portable unit would enable random checks of fruit in the field
or in the wholesale or retail store.
On-harvester estimation of grain protein content for precision
agriculture and estimation of the sugar content of fibrated sugar
cane (beet) in sugar mills.
30.
Sweet Corn - insect damage and insect detection
Coal - moisture determination
Citrus - quality attributes
Pineapples, mango's, strawberries - quality attributes
Stone fruit - quality attributes
Melons - quality attributes
Determination of pharmaceutical dosage forms
Monitoring of PVC industrial blending process
Identification of inorganic preservative-treated Wood
Analysis of polymorphs
Determination of Adulteration of African Essential Oils
Protein quantification within lipid implants
31. LYOPHILIZED PRODUCTS
Lyophilization is usually performed to increase the storage
stability of hydrolytically unstable drugs that are intended to be
used as injectables or to achieve an instantly soluble oral
dosage form.
Normally
the moisture content of lyophilized products is determined by
time-consuming methods, such as Karl Fischer titration. In
addition, the procedure requires the vial to be opened for analysis.
NIR
Moisture determination with NIR diffuse reflectance techniques
can be performed in a fast and non invasive manner through the
glass vials.
32. MEASURE THE NIR SPECTRUM OF EACH LYOPRODUCT
a) The principal set up which
to achieve the NIR spectra
in reflection mode
b) The illumination is realized
through a 40 Watt tungsten
halogen lamp which
illuminates the vial
c) The NIR reflection is
collected in a fibre optic
cable which is connected to
the NIR PDA spectrometer
with 256 diodes and a
wavelength range of 1000
nm to 2100 nm
33.
Packaging is the last step in the production line of a
pharmaceutical product. To ensure the product safety of
pharmaceuticals, a last identity check of the product on
the packaging line would be highly desirable.
Such an inspection system based on the combination of a
conventional high resolution camera with an on-line
diode
NIR spectrometer ranging from 900 to 1700 nm at 6 nm
resolution has been developed recently. The system is
supposed to perform a 100% identity check at full line
speed(i.e. 12,000 tablets per minute) before closing the
blister. The potential of this type of equipment has been
evaluated in a feasibility study .
