Post on 23-Dec-2021
The Leader in Spectroscopy
Výběr z aplikací infračervené spektrometrie
Ján Pásztor, Nicolet CZ s.r.o.
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Fourier Transform Infrared Spectroscopy
• IntroductionElectromagnetic radiation
Vibrational spectroscopy
• Instrumentation Interferometry
The Fourier Transform
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10 10 10 10 10 10 10 109 7 5 3 1 -1 -3 -5
Wavenumbers
x-rays
ultraviolet
visible
near-IR
mid -IR
far-IR
microwave
radio waves
Wavelength in microns
nuclear electronic vibrational
10 10 10 10 10 10 10 10
transitions
-5 -3 -1 1 3 5 7 9
rotational
Electromagnetic Spectrum
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Harmonic Vibrations
• The vibration of a diatomic molecule can be approximated by the vibration of a spring
• The wavenumber of the vibration equals:
with m=
1
2x
c
k
m1m2
m1 + m2
m
RRee--DDRR RRee RRee++DDRR
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Quantized harmonic, anharmonic
hh/2/2pp ((k/k/M).(M).(νν+1/2)+1/2)
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Selection Rules for Infrared Activity
• The frequency of the light must be identical to the frequency of the vibration (resonance)
• The dipole of the molecule must change during the vibration
• The direction of the dipole change must be the same as the direction of the electric field vector
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Cl H N N
Dipole Change
• To absorb energy, the dipole must change when the transition occurs
• The intensity of the absorption is proportional to the magnitude of the dipole change
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C CC C
Stretching Deformation
Bending Twisting
C
+ -
15
20
25
30
35
40
45
50
55
60
65
70
75
80
85
90
95
100
%T
1000 1500 2000 2500 3000 3500 4000
cm-1
Molecular Vibrations
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1000 1500 2000 2500 3000 3500
Wavenumbers (cm-1)
Fingerprint region
Functional groups
Polyatomic Molecules
• The spectrum becomes more complex as the number of bonds increases
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Non-linear Triatomic Molecule (H2O)
• 3 normal vibrations (3N-6)
• Coupling of vibrations bendingbending
(1595 cm(1595 cm--11))
symmetricsymmetric
stretchingstretching
(3657 cm(3657 cm--11))
asymmetricasymmetric
stretchingstretching
(3756 cm(3756 cm--11))
E1
E2
E E
En
erg
y
Fre
qu
en
cy
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Fixed Rotations in a Lattice (-CH2)
scissoringscissoring
(~1463 cm(~1463 cm--11))
twistingtwisting
(~1300 cm(~1300 cm--11))
waggingwagging
(~1280 cm(~1280 cm--11))
+ +
+-
CHCH22 rocking at 720 cmrocking at 720 cm--11
• Since the atoms are fixed in a skeleton, more bending vibrations occur
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Overtones
Occur close to INTEGER
MULTIPLES Of FUNDAMENTAL Bands.
For example: C-H Overtones Will Occur Near:
First Overtone
2960 cm-1 (C-H Stretch) * 2 = 5920 cm-1
Second Overtone
2960 cm-1 (C-H Stretch) * 3 = 8880 cm-1
The intensity of the absorption depends on the degree of
anharmonicity and gets weaker with increasing overtones
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Combination Bands
COMBINATION Bands Appear Near The Sum Of
Two Or Three FUNDAMENTAL Bands
For Example: A C-H Combination Will Occur Near…
2960 cm-1 (C-H Stretch) + 1460 cm-1 (C-H Bend)
= 4420 cm-1
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NIR spectrum
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0.5
700 900 1100 1300 1500 1700 1900 2100 2300 2500
Wavelength (nm)
Ab
so
rban
ce (
Lo
g 1
/R)
Combination
1st Overtone
2nd Overtone
3rd Overtone
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Sources, Beamsplitters and Detectors
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Source, Beamsplitter, and Detector Combinations Depend on Application
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FT-IR System
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+ =
+ =
Wave Interactions (Interference)
• In-phase Constructive
interference
• Out-of-phase Destructive
interference
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DetectorDetector
Michelson Interferometer-1
Fixed mirrorFixed mirror
l 0 -l
InterferometerInterferometer
Moving mirrorMoving mirror
IR IR
SourceSource
BeamsplitterBeamsplitterBM
Path difference = 0
BMBF =
BF
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Michelson Interferometer-2
Detector
Fixed mirrorFixed mirrorInterferometerInterferometer
Moving mirrorMoving mirror
l 0 -l
IR IR
SourceSource
BeamsplitterBeamsplitterBM
Path difference = 1/4
BM - 1/8 BF =
BF
DetectorDetector
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Michelson Interferometer-3
Fixed mirrorFixed mirror
DetectorDetector
InterferometerInterferometer
Moving mirrorMoving mirror
l 0 -l
IR IR
SourceSource
BeamsplitterBeamsplitter
Path difference = 1/2
BM - 1/4 BF =
BM
BF
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Fixed mirrorFixed mirror
BeamsplitterBeamsplitter 0 0 --
DetectorDetector
InterferometerInterferometer
IR IR
SourceSource
Michelson Interferometer-4
Moving mirrorMoving mirror
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Path difference
Signal at the Detector
Vo
lta
ge
0 1/4 1/2 3/4
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The Interferogram
One Wavelength Many Wavelengths
020406080100120140
-1.0
-0.5
0.0
0.5
1.0
010002000300040005000
-3
-2
-1
0
1
2
3
4
Data Points Data Points
Vo
lts
Vo
lts
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Sampling the Interferogram
Source
He-Ne laser
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Dynamic Alignment
Fixed mirror
x 0 -x
Beamsplitter
Laser diodes
He-Ne laserMoving mirror
XYR
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Dynamic Alignment Advantages
• Better short term stability
• Better long term stability
• Better spectral line shapes
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5001000150020002500300035004000
5
10
15
20
25
30
35
40
Wavenumbers
Fast Fourier Transformation
FFT
010002000300040005000
-3
-2
-1
0
1
2
3
4
Data Points
V
o
l
t
s
Interferogram Spectrum
E
m
i
s
s
i
v
i
t
y
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Transmission Spectrum
170018001900210022002300
-3
-2
-1
0
1
2
3
4
Data Points
Vo
lts
170018001900210022002300
-3
-2
-1
0
1
2
3
4
Data Points
Vo
lts
5001000150020002500300035004000
5
10
15
20
25
30
35
40
Wavenumbers
Em
issiv
ity
5001000150020002500300035004000
5
10
15
20
25
30
35
40
WavenumbersE
mis
siv
ity
bkg: FFT
sam: FFT
5001000150020002500300035004000
20
30
40
50
60
70
80
90
Wavenumbers
Tra
nsm
itta
nce
Ratio
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Summary
Advantages of FT-IR Instruments
• Multiplex advantage (Felgett’s) All wavelengths are measured simultaneously
• Throughput advantage (Jacquinot’s) Higher energy throughput (larger apertures)
• Precision advantage (Connes’) Internal calibration is derived from He-Ne laser (precision = 0.01 cm-1)
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Technique Choice
• Analytical goals Quantitative
Qualitative
• Sample dependent factors Size
Chemical makeup of sample
• Optimization
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Sampling Techniques and Applications
• Transmission
• Attenuated Total Reflectance - ATR
• Diffuse Reflectance – DRIFTS
• Gas Analysis
• Semiconductor
• Oil Analysis
• GC/FT-IR
• TGA/FT-IR
• Mobile/Portable FT-IR
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Advances in Accessory Design
• Automatic set-up of system parameters and experiment
• Rugged, permanently aligned, plug & play design
• On-line help and tutorials
• Design for fast purge
• Operation integrated with spectrometer and software
• Automatic tests ensure proper accessory operation
• System checks ensure high quality spectra are collected
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Transmission Analysis
• Requires sample preparation
• Proper pathlength required Strong absorbers - short pathlength
Weak absorbers - long pathlength
• Solids, liquids, gases
• Qualitative analysis
• Quantitative analysis
• Maximum sensitivity
• Low cost
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The peak at 3651 cm-1
was used to quantify the
antioxidant butylated hydroxy
toluene (BHT) in the poly-a-olefin
(PAO) lubricant
Analysis of Antioxidant Levels in Lubricating Oil
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Attenuated Total Reflectance
• Versatile and non-destructive technique for infrared sampling
• Requires minimal or no sample preparation
• Useful for surface characterization
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Considerations for ATR Analysis
• Refractive index of ATR and sample
• Pathlength requirements
• Spectral range of interest
• Phase of sample: solid, liquid, gel
• Chemical properties
• Hardness of sample
d p =
2p natr (sin2 q) -nsample
natr( )2[ ] 1/2
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Attenuated Total Reflectance ATRSingle Bounce vs Multi-bounce
• Small sampling area
• Use for strong absorbers
• Solid samples
• Broad sampling area provides
greater contact with the sample
• Use for weak absorbers or dilute
solutions
ZnSe Internal Reflection Element
Penetration depth
up to two micronsPlunger
Crystal Cap
IR Beam
Crystal
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Properties of ATR Crystals
Material
ATR Spectral
Range (cm-1)
Refractive
Index
Depth of Penetration (µ)
(at 45º & 1000 cm-1) Uses
Germanium 5,500 - 675 4 0.66
Good for most samples.
Strong absorbing
samples, such as dark
polymers.
Silicon8,900 - 1,500 &
360-1203.4 0.85
Resistant to basic
solutions.
AMTIR 11,000 - 725 2.5 1.77Very resistant to acidic
solutions.
ZnSe 15,000 - 650 2.4 2.01 General use.
Diamond 30,000 - 200 2.4 2.01
Good for most samples.
Extremely caustic or hard
samples.
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Analysis of Fibers Using Single Bounce ATR
• No sample preparation
• Non-destructiveto the sample
• Shallow depthof penetrationgood for dark polymers
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Identifying Fiber Threads Inside An Automotive Hose
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ATR Summary
• Ease-of-use
• Rapid qualitative and quantitative analysis
• No sample preparation
• Multiple crystals for various sampling needs
• Best technique for condensed phase samples
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Diffuse Reflectance (DRIFTS)
• A multi-modal technique Specular Reflectance
Diffuse Specular Reflectance
“True” Diffuse Reflectance
• Kubelka-Munk equation Absorbance-like results
R = reflectance with infinite depth
K = molar absorption
S = scattering coefficient
F(R) = (1-R)2
2R =
KS
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Compound Parabolic Concentrator
• Independent of sample height
• Reduces sample packing effects
• Minimizes front surface reflection (specular component)
• Efficient high throughput collection optics
• Sample positioned below optics
• No damage to optics from sample spills
Input / output optics
CPC
Powder sample cup
CPC Design
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DRIFTS Analysis of Pharmaceutical Powders
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DRIFTS Analysis of Pharmaceutical Powders
Analytical Goal
• Simplified sample preparation
• Identification of key ingredients
Ibup ro fen Powder
0.3
0.4
0.5
Lo
g(1
/R)
Nap roxen Sodium Powder
0.2
0.4
0.6
Lo
g(1
/R)
Ps eudoephedrine H Cl Powder
0.50
0.55
0.60
0.65
0.70
0.75
Lo
g(1
/R)
600 800 1000 1200 1400 1600 1800
Wav enumbers (cm-1)
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Benefits of Diffuse Reflectance
• Good choice for dilute powders
• Analysis of non-reflective materials
• Minimal sample preparation
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FT-IR Gas Analyzer
• Detects pollutants CO, NOx, HC
NH3, HCN, N2O
• Nexus Gas Analyzer 2 meter gas cell
MCT-A detector
• Detection limits – less than 1 ppm
• 0.09 cm-1 resolution
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NOx Reduction in Diesel Exhaust
• Diesel engines are run “lean,” i.e. with excess air during combustion
• “Naturally” low hydrocarbon and CO emissions but high NO and NO2
emissions
• “Urea” with catalyst can reduce NO and NO2
• However, concern is that HCN is generated
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HCN Emissions
• “Urea” injection reduced NO and NO2 and can be tuned to minimize HCN generation
Abs
HCN 97 ppm in exhaustHCN 0.6 ppm in exhaustHCN standard
-0.2
-0.0
0.2
0.4
0.6
0.8
1.0
3250 33003350cm-1
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Semiconductor Wafer Analysis
• Semiconductor devices are manufactured on silicon wafers, using successive layers of metals and insulators
• Many devices are produced from each wafer. As many as 300 PentiumTM like devices, or more than 800 memory chips, can be produced from a single 8” or 12” diameter wafer
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Semiconductor Analysis
• The samples were analyzed using the Nicolet® ECO 3000
• Samples were scanned in transmission (silicon is transparent to infrared radiation)
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Si-H Variation
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Conclusion
• Hydrogen concentration can effect the dielectric constant in these films
• Customer was able to identify a heating problem with the wafer platen in the deposition system, based on the shape of the center region of the profile
• After adjusting the temperature parameters in the system, uniform films were produced and device yields reached 98%
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Approaches for Lubricant QCTotal Process Checking
• Incoming ingredient testing Base oil and add-pack lot consistency
• Blended product analysis Additive levels
• Outgoing product verification Assure product correct for shipment
• Used Oil Analysis Engine Monitoring
• Edible Oil Analysis Product Consistency
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Integra Oil Analysis
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Spectral Regions of Interest for Used Oil
0.2
0.3
0.4
0.5
0.6
0.7
0.8
Absorbance
1000 1500 2000 2000 3000 4000
Wavenumber
Water
CarboxylCarboxyl
Soot
NitroSulfate
Glycol
Fuel
Phosphate
Anti-wear
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Polymer Additive Identification by GC/FT-IR
• Reverse Engineering Customer wants to deformulate competitive product
Product is complex polymer with several additives
GC analysis alone was inconclusive
• Infrared spectroscopy was necessary for identification of additives
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Nicolet® Nexus® GC/FT-IR System
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Polymer Additives by GC/FT-IR
Real-Time Display
8 cm-1 Resolution
0.74 sec/spectrum
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GC/FT-IR Peak Identification
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TGA/FT-IR Rubber Gasket Characterization
•High pressure and temperature application
•Gasket from backup supplier fails
•TGA only reveals small difference
•TGA/IR reveals compositional differences
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TGA/FT-IR System
• TGA
• FT-IR spectrometer
• TGA/IR interface
• OMNIC Series software
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TGA/IR Data of Rubber Gaskets
• 8 cm-1 resolution
• DTGS detector
• 10.0 sec time resolution
• OMNIC Series software
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TGA/IR Spectra of Rubber Gasket Samples
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Library Search Results
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Mobile and Portable Infrared Analysis
• Incident Preparedness and Response (IPAR)
•First Responders
•Fire Fighters
•Clandestine Lab Investigators
•WMD/CST
•US Army/US Navy
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Implementation
• Mobile system offers full sampling flexibility in a small footprint
Expandability and flexibility
AC power necessary
GLP or 21 CFR Part 11 software tools
• Portable system offers rapid setup and simplicity of operation
Compact, integrated, transportable system
Flexible power sources - AC, 12 volt or battery
Laptop computer compatibility via USB
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Mobile Solution
Dynamic Interferometer alignment
Rugged--Sealed and desiccated or Purgeable
Smart accessories ease sample preparation
Full OMNIC capability
IR Microscope ready
GLP, Validation
21 CFR Part 11 Compliance tools
Full laboratory capability in a small footprint
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Hazardous Sample Analysis Accessory
• Smart Golden Gate Diamond ATR
• Natural Type IIa diamond
• Diamond brazed to tungsten
carbide disk
• Top plate removable for glove box
loading
• Sample anvil isolates sample from
environment
• Extremely easy-to-use and simple
decontamination
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Hazardous Materials Analysis Mustard HD
-0.00
0.01
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0.05
0.06
0.07
0.08
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0.10
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0.13
0.14
Ab
so
rba
nce
1000 1500 2000 2500 3000 3500
Wav enumbers (cm-1)
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Conclusions - Sampling Techniques
• Thermo Electron FT-IR spectrometers provide a broad range of analytical solutions
• We develop new sampling technologies based upon your sampling needs
• Speed, resolution and sensitivity of our systems can be tuned to your experiment
• Let us know how we can help solve your analytical problems
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Human Hair Analysis
• Verify the fiber to be consistent or inconsistent with hair fromthe suspect
• FT-IR microscope w/ ATR objective
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Surface Analysis of Hair
• ATR, excellent surface analysis tool
• Maximizes surface response
Hair without Hairspray
Hairspray on Hair
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
Ab
sorb
an
ce 1000 2000 3000 4000
Wavenumbers (cm-1)
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Surface Analysis of Hair
• Difference FT-IR bands consistent with PVA hair spray
• ATR microscopy - surface sensitive, non-destructive
Subtraction Result: Hairspray on hair - hair
PVA from Library
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
Ab
sorb
an
ce 1000 2000 3000 4000
Wavenumbers (cm-1)
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Fiber from Crime Scene
• Fiber Diameter - 20 microns
• ATR Objective Sample Area - 7 microns
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Micro ATR Fiber Spectrum
20 micron diameter fiber by Micro-ATR
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
A
b
s
o
r
b
a
n
c
e
1000 1500 2000 2500 3000 3500 4000
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Paint Chip Analysis
• Automotive Paint Identification
• Multilayered, 20-25 microns each
• Redundant Aperturing Required
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View-Thru Aperturing - 15x15 microns
Analyze !Both Apertures
Lower ApertureNo Apertures
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Paint Spectra
Grey Layer - 25 microns thick
Red Layer - 17 microns thick
Clear Layer - 25 microns thick
-0.4
-0.2
0.0
0.2
0.4
0.6
0.8
1.0
1.2
A
b
s
o
r
b
a
n
c
e
1000 1500 2000 2500 3000 3500 4000
Wavenumbers (cm-1)
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NIR Spectroscopy
Advantages
• Easier Remote sampling
• No sample preparation
• Glass is “transparent”
• Quick data collection
Disadvantages
• Difficult or impossible to interpret spectra
• More complex to develop methods
• Difficult to add extra compounds to a sample ID method
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SabIR Near-IR Fiber Optic Accessory
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NIR Fiber Optic Sampling
Aspirin Tablet in Packaging
0.5
1.0
Abso
rbance
6000 8000
Wavenumbers (cm-1)
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Polyvinyl Chloride / Vinyl Acetate Copolymers
PVC100
PVC/AC 90/10
PVC/AC 87/13
PVC/AC 81/17
-0.10
-0.05
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
Abs
orba
nce
5000 6000 7000 8000 9000 10000
Wavenumbers (cm-1)