FTIR-PHOTOACOUSTIC SPECTROSCOPY
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Niina Koivikko, Christian Hirschmann, Satu Ojala, Riitta L. Keiski
Mass and Heat Transfer Process Laboratory
Department of Process and Environmental Engineering
University of Oulu
POKE workshop 3
Tallinn 11.-12.12.2013
INTRODUCTION TO
PHOTOACOUSTIC SPECTROSCOPY
• The photoacoustic effect is based on the absorption of infrared
radiation by the sample which is heated up and the absorbed
heat is transferred into the surrounding gas.
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• pressure waves are
created in the surrounding
gas which are detected by
a sensitive microphone
and converted into an
electrical signal. (Bruker)
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INTRODUCTION TO
PHOTOACOUSTIC SPECTRSCOPY
• Set-up for FTIR transmission spectrometer
• Set-up for FTIR Photoacoustic spectrometer
Light
source FTIR
Sample gas
Photoacoustic
detector
Gas
cell
For solid, semi-
solid, liquid and
gaseous samples
ADVANTAGES OF PAS OVER
TRADITIONAL FTIR SPECTROSCOPY
Versatile and easy sampling Suitable for different kind of samples and no sample preparation
needed
Zero- background method Long term stable
Small optical path length
Small sample volume (contactless and nonconsuming)
Linear signal
Capability for depth profiling
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FTIR VS. FTIR-PAS
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MEASUREMENT DEVICE IN MASS AND
HEAT TRANSFER PROCESS LABORATORY,
UNIVERSITY OF OULU
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VERTEX 80V FTIR (BRUKER) PA301(GASERA)
Uotila et al. 2010
BRUKER FTIR WITH PA301
• Measures solid, semi-solid and liquid samples.
• Hard crystalline materials or powders can be measured.
• Hightly absorbing ”black” samples can be measured also.
• For sample surface morphology and depth profiling
measurements.
• Ultra-sensitive optical microphone based on a MEMS cantilever
sensor coupled with a laser interferometer to measure
microscopic movement of the cantilever sensor.
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BRUKER FTIR WITH PA301
Dark samples
pharma quality control
soil samples
paper and wood analysis
oil analysis
tissue and hair samples
polymers
paint and pigment analysis
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REFERENCES
• J. Raittila, C. Hirschmann, A. Helle, J. Tenhunen, S. Ojala, K. Rahkamaa-Tolonen R- L.
Keiski, Measurement of Volatile Organic Compounds in Hot Emission Streams with
Cantilever Enhanced Photoacoustic Detector, Pittcon, Orlando 12.3.2012.
• C. Hirschmann, N. Koivikko, J. Raittila, J. Tenhunen, S. Ojala, K. Rahkamaa-Tolonen,
R. Marbach, S. Hirschmann, R. L. Keiski (2011), FT-IR-cPAS - New Photoacoustic
Measurement Technique for Analysis of Hot Gases: a Case Study on VOCs, Sensors 11
(2011) 5270-2589.
• Gasera, www.gasera.fi
• Bruker, www.bruker.com
• J. Uotinen, J. Raittila, I. Kauppinen, J. Kauppinen, Cantilever Enhanced Photoacoustic
FTIR Challenges ATR and Diffuse Reflectance Techniques, Pittcon, Orlando 2010.
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FTIR PHOTOACOUSTIC GAS SPECTROMETER PROTOTYPE MEASUREMENTS FTIR-CPAS
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Case study on VOCs
FTIR PHOTOACOUSTIC GAS SPECTROMETER PROTOTYPE MEASUREMENTS FTIR-CPAS
• Prototype measurement device for industrial measurements.
• The PA cell and all parts heated up to 200 degrees.
• Case study on Volatile Organic Compounds.
• What needs to be taken into account:
A) VOC compounds mixture selectivity+ability to
measure multicomponent gas mixtures
B) water vapour subtraction of water+linearity
C) Trace concentrations sensitivity
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Hirschmann et al., 2011
Acetone
Ethanol
Isobutanol
Isopropanol
Methanol
n-butanol
Perchloroethylene
Methoxypropanolacete
Methylacetate
Methylethylketone
o-xylene
m-xylene
p-xylene
Dimethylformamide
Dichloromethane
Butylacetate
Toluene
Christian Hirschmann
Cantilever-enhanced photoacoustic
spectroscopy in the analysis of volatile
organic compounds
Doctoral defense 14.12.2013
(University of Oulu)
Electronic version available at:
http://www.vtt.fi/vtt_search.jsp?target
=julk&form=sdef&search=%28py%3E2011+
AND+jt=c1%29
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