BASICS OF INFRARED AND RAMAN SPECTROSCOPY · NIR spectrum Spectroscopy: instrumentation 31 RAFA 2013 (Prague, 5 November2013) Dispersive instruments (NIR, MIR & Raman) (Williams and

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RAFA 2013 (Prague, 5 November 2013)

Vincent Baeten, Juan Antonio Fernández Pierna, Philippe Vermeulen, Pierre Dardenne

Département Valorisation des Productions Agricoles

Unité Qualité des Produits

Walloon Agricultural Research Centre

(CRA-W, Belgium)

[email protected]

BASICS OF INFRARED AND RAMAN SPECTROSCOPY

2nd RAFA workshop on : Infrared spectroscopy, Raman spectroscopy

and chemometrics for monitoring of food and feed products, lab-to-

the-sample

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Nickolay Lamm

Source : http://www.lesoir.be/

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- 1st generation

Example : Kjeldahl

chemical reaction + physical separation

- 2nd generation

Example : chromatography techniques

physical separation + physical detection

- 3rd generation

Example : spectrometer/sensor

physical detection + data treatment/chemometrics

Evolution of analytical solutions

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Pará, Brasil

(30/12/2012)

Look, a rainbow!

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Violet: 400 - 420 nm

Indigo: 420 - 440 nm

Blue: 440 - 490 nm

Green: 490 - 570 nm

Yellow: 570 - 585 nm

Orange: 585 - 620 nm

Red: 620 - 780 nm

The rainbaw colours … 7 … are you sure?

Source : wikipedia, http://teaching.shu.ac.uk/hwb/chemistry/tutorials (2012)

Wavelength (nm)

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Discovery of Near InfraRed Radiation

• 17 March 1800

• William Herschel,Astronomer Royal attemptsto find out the spectralregion responsible for heatformation in his telescope.

•The NIR is discovered.

•Philosophical Transactionsof the Royal Society 90:255-83

(Source : Ian Murray, 2012)

The electromagnetic spectrum …

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� Absorption occurs when energy from the radiative source is absorbed by the material. (e.g. infrared absorption, UV and DAD detectors)

� Reflection occurs when incident radiation is reflected by a material. (i.e. internal reflection)

� Emission occurs when radiative energy is released by the material. (e.g. Fluorescence, fluorescence detector)

� Elastic scattering occurs when incident radiation is scattered by a material. (e.g. Rayleight scattering, ELSD detector)

� Inelastic scattering occurs when the is an exchange of energy between the radiation and the matter that shifts the wavelength of the scattered radiation. (e.g. Raman scattering)

� … (Coherent, resonance, impedance, …)

Nature of the interation of radiation with

materials (molecules)

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Greenglass

Internal

reflected ray

Transmitted ray

red-blue

attenuated(Source : Ian Murray, 2012)

Nature of the

interation of

radiation with

materials

(molecules)

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Greenglass

i i

r

reflection refraction dispersion absorption

r

iRI

sin

sin=

Aλ = log1/T ∝ conc*path


Nature of the interation of radiation with materials (molecules)

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groundgreenglass

Indicatrix of diffuse+specularreflected light

scattering

No lightAλ= log1/R ∝ conc*path


Nature of the interation of radiation with materials (molecules)

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Ia

I0

Ir

ABSORBANCE oABSORBANCE or optical densityr optical density

====

R

1LogA

REFLECTANCEREFLECTANCE IrR=

I0Opaque samplesPowdersNIR & MIR (Raman)

TRANSMITANCETRANSMITANCE ItT=

I0Clear samplesGases, liquidsNIR & MIR (Raman)

Ia

I0

It

====

T

1LogA

ABSORBANCE ABSORBANCE or or opticaloptical densitydensity

Mode of measure of spectra

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• If vibration changes the dipole moment then bond can absorb photons

• A photon of exactly the right frequency is absorbed & excites the bond to a higher vibrational state

• Frequency = qualitative analysis:IDENTITY

• Amplitude = quantitative analysis:AMOUNT

C H

• Covalent bonds share electrons between atoms in a molecule

E=hν

1.09 Å

• Bonds have length, strength & direction unique to each pair of atoms

• Bonds act like springs joining atoms

• Bonds vibrate at unique frequencies due to atomic masses & ‘stiffness’

C H

+_


Nature of the covalent bond

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(So

urc

e : I

an M

urr

ay, 2

012)

Potential energy associated to a molecule

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UV VIS IR Microwave Radio

Frequency

Wavelength (nm)

Wavenumber (cm-1)

800 2500

4000 400

� Near-infrared spectroscopy

(NIR)

� Mid-infrared spectroscopy

(MIR)

Fundamental vibrationsOvertone and

combination vibrations

∂ µ /∂q ≠ 0 ∂ µ /∂q ≠ 0

12500

25000

Energy


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• Organic compound exposed to electromagnetic radiation, can absorb energy of only certain wavelengths (unit of energy)– Transmits or scatters energy at other wavelengths

• Changing frequencies to determine which are absorbed and which are transmitted produces an absorption spectrum

• Energy absorbed is distributed internally in a distinct and reproducible way

Mid-infrared (MIR/IR) spectroscopy - theory

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An example of near infrared (NIR) spectra

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0,3

0,8

1,3

1,8

1.100 1.300 1.500 1.700 1.900 2.100 2.300 2.500A

bso

rba

nce

(Lo

g 1

/R)

Wavelength (nm)

Wheat (15.8 %)

Wheat (21.3 %)

Water (100 %)

NIR spectra : main spectral bands

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0

0,5

1

1,5

2

1.100 1.300 1.500 1.700 1.900 2.100 2.300 2.500

Ab

sorb

an

ce (

Log

1/R

)

Wavelength (nm)

Honey (Rapeseed)

Saccharose

Water

NIR spetra : honey spectrum

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0

0,1

0,2

0,3

0,4

05001.0001.5002.0002.5003.0003.5004.000

Ab

sorb

an

ce (

Log

1/R

)

Wavenumber (cm-1)

Mid-IR

Mid-IR

Example of mid infrared (IR, MIR) spectra

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Raman theory : Raman effect

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1

3

hνν νν

RA

Y

hνν νν

R(S

t)

hνν νν

R(a

St)

2

1

0

E

1st

electronic

excited state

Virtual

states

Ground

electronic state

hνν νν 0

hνν νν 0

hνν νν 0

hνν νν I

R

Figure : Energy level diagram showing the basic transitions involved in

infrared, Rayleigh & Raman effects. (Adapted from Nakamoto, 1986;

Baranska, 1987 and Bulkin, 1991)

Raman scattering


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Raman scattering

� Origin = same type of vibrations as infrared spectroscopy

� Appears when a molecule irradiated with a monchromatic light

– some photons scattered at same frequency (Rayleigh scattering)

– some photons scattered at different frequencies (Raman scattering)

– Rayleigh scattering frequency – Raman scattering frequen cy = corresponds to energy of vibrational transition

� Some characteristics : any monochromatic light can be used, Raman effect is instantaneous (vibrational absorption is fast but slower thanRaman)


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0

0,1

0,2

0,3

0,4

0,5

0,60

0,1

0,2

0,3

0,4

0,5

0,6

0 500 1.000 1.500 2.000 2.500 3.000 3.500 4.000

Ab

sorb

an

ce (

Log

1/R

)

Wavenumber (cm-1)

Mid-IR

Raman

Sca

tte

rin

g i

nte

nsi

ty

Example of mid infrared (NIR) and Raman spectra

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Mathematical

model+

Data-base

Reference

values

Spectrum

Mathematical

modelPredicted

values+

Quantitative analysis

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Feed & Feed ingredients

Large spectroscopic and microscopic data-bases

Merging data-bases :

CRA-W (BE) & AUNIR

(UK) data-bases

Network of Network of

instruments instruments

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Quality control for different companies

- Cereals based companies (e.g. flour, bread or beer

producers)

- Reception stage - During the production stages (on-line)- Final products

- Bioethanol companies

- Screening tool to optimize the segregation of raw material - Track the fermentation and conversion - Rapid analysis of by-products

- Breeding programs

- Unique tool that allow the analysis of the cereals in the field

- Able to handle the huge number of samples

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Norm : example

for seeds and

kernels (Cereals,

Oil seeds, …)

EN 15048

“Cereals - moisture

and protein -

Near-Infrared-Spectr

oscopy in whole

kernels”

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See FEED module of the course

Norm : example

for seeds and

kernels (Cereals,

Oil seeds, …)

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Wavelengthselector

Sample

Wavelengthselector

Detector

Source

Source Sample

Detector

Detector

a) Transmission mode

b) Reflection mode

Polychromatic radiation

Polychromatic radiation

Wavelength (nm)

NIR spectrum

Spectroscopy : instrumentation

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Dispersive instruments (NIR, MIR & Raman)

(Williams and Norris, 2001)32


Dispersive NIR instruments

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Fourier Transform (FT) NIR instruments

(NIR, MIR & Raman)

(Williams and Norris, 2001)

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(NIR, MIR & Raman)

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http://www.perkinelmer.com/


(NIR, MIR & Raman)

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(NIR, MIR & Raman)

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(NIR, MIR & Raman)

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200-1100 nm1100-2500 nm

STATIONARY GRATING

Diode array instruments

Data treatment

sabs

λ

InGaAs detector

128 diodes

GratingSource

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Diode array instruments

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Step3

Step4

Step5

Step1

Step2

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At-line, on-line & in-line instruments

Sébastien Gofflot, CRA-W

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Source : Kaiser

optical systems

www.kosi.com

Ethanol bio-transformation – on-line Raman

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Schematic of the n-around-1 fiber-optic probe.

(Mc Creery, 2000)


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http://www.perkinelmer.com


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NIR

GPS

Field application

Dr Georges Sinnaeve, CRA-W

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0 200 m100100

Protein (% DM)

11.25-11.5011.51-11.7511.76-12.0012.01-12.2512.26-12.5012.51-12.7512.76-13.0013.01-13.2513.26-13.50

Dr Georges Sinnaeve, CRA-W

Field application

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And more instruments …

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TruScan* Handheld Raman for Material Identification

http://www.thermoscientific.com


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Intensity information

(i.e. absorbance)

Frequency information

(i.e. wavelengths)

Spatial information


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At your service …

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A team at your service

Dr Vincent Baeten Mrs Claudine Clement

Dr Juan A. Fernández Pierna Mrs Anne Mouteau

Ir Philippe Vermeulen Ms Sandrine Mauro

Ing Bernard Lecler Ms Emma Mukandoli

Dr Ouissam Abbas Mr Marie Collard

Dr Pascal Veys Mr Nicolas Crasset

Dr Marie-Caroline Lecrenier Ms Marianne Flahaut

Ing Olivier Minet Mr Quentin Arnould

Ir Quentin Ledoux Mr Benoît Scaut

Mr Alexandre Quoitot Mr Nicaise Kayoka Mukendi

Ir Damien Vincke Mr Stéphane Brichard

Dr Pierre Dardenne (Head of the Department)

Dr Georges Sinnaeve, Ir Frédéric Dehareng, Ir Clément Grelet (U14)

Dr Gilbert Berben, Dr Olivier Fumière (U16)

Documents

BASICS OF INFRARED AND RAMAN SPECTROSCOPY · NIR spectrum Spectroscopy: instrumentation 31 RAFA 2013 (Prague, 5 November2013) Dispersive instruments (NIR, MIR & Raman) (Williams and