ANALYTICAL PYROLYSIS

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Christmas Seminar Cruise 4.12.2003
ANALYTICAL PYROLYSIS A fingerprinting tool for
complex organic samples
Tero Lehtonen Environmental Chemistry Department
of Chemistry University of Turku Finland
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Short introduction to analytical pyrolysis

• What is it?

• Why is it a powerful method for complex and
  difficult organic samples like natural materials
  and polymers?

• How is it performed?

• What kind of practical applications?

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What is analytical pyrolysis?

• study of organic molecules by rapid thermal
  fragmentation in the absence of oxygen followed
  by a GC/MS analysis of those fragments

Chromatogram
Mass spectra
Sample molecule
Pyrolysis products
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Benefits of analytical pyrolysis TOP 5
1. Minimal sample preparation (usually only
drying and homogenisation) 2. Minimal sample
consumption (from few to several hundreds of
micrograms) 3. Suitability for complex mixtures
and composites (component molecules behave
independently in pyrolysis and generate some
very specific products) 4. Selectivity for
organic constituents (allow analysis of impure
high ash/inorganic content samples) 5. High
reproducibility (if sample handling and analysis
correctly made)
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Analytical instrumentation

• Typical on-line analytical instrumentation
  includes

1. Helium source 2. Pyrolysis equipment 3. Gas
chromatograph 4. Mass spectrometry 5. Data
handling
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Pyrolysis instrumentation

• In practise
• sample is weighed in the small quartz tube placed
  into the Pt coil of the pyroprobe
• probe is inserted into the differentially heated
  interface (150-200oC) connected directly to the
  GC injector
• pyrolysis probe is resistively and very rapidly
  heated to pyrolysis temperature (e.g. 600oC /
  10s)
• released volatile fragments are swept (He as a
  carrier gas) into the GC or optionally collected
  in the cryogenic trap

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What is pyrolytic fingerprint?

• as a result each organic sample generate an
  unique pyrolytic fingerprint (chromatogram
  including released pyrolysis products) to study

some specific individual fragments
OR
total product distributions
Carbohydrate descriptors (III) 4.3 Protein
descriptors (III) 6.2 Aliphatics (IV) 28.5
Lignin descriptors (V) 19.7 Other
aromatics (VI) 32.1
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Applications of analytical pyrolysis

• Most common applications include

• Industrial applications purity tests, polymer
  analysis, compositional analysis of pulp
  products, analysis of cigarette smoke etc.
• Environmental/biological/geological
  applications analysis of organic matter in
  water, soil and air particles, analysis of
  bio-polymers, chemotaxonomic studies of
  micro-organisms etc.
• Cultural applications analysis of materials in
  art and archaeology
• Forensic applications comparative analysis of
  different forensic evidences

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Cultural applications

• Valuable art and archaeological objects are
  often complex materials and difficult to analyse
  because you cannot destroy them with chemical
  methods like solvent extraction
• Even if pyrolysis itself is destructive method,
  analytical pyrolysis is virtually non-destructive
  because of extremely small sample sizes needed

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In archaeology

• Why do the Egyptians look so pretty after so many
  years?
• Py-GC/MS fingerprinting can give us valuable
  hints about constituents of ancient embalm
  materials, which are usually some complex natural
  waxes and have extreme low volatility after their
  ageing process

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In art and restoration

• Why did Titian paint so much better than most of
  our modern artists?
• Py-GC/MS fingerprinting of different varnish and
  paint layers can be used to clarify paint recipes
  and techniques of old masters, to select
  appropriate restoration methods or to find out if
  the painting is later re-worked

Madonna of the cherries, 1516-1518 Titian
(Tiziano Vecellio), Venice, Italy
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Forensic applications

• Many forensic evidence materials present a
  problem to the common methods of analytical lab
  because they are small, non volatile and contain
  also inorganic constituents.
• Py-GC/MS fingerprinting is appropriate method
  for discriminative and comparative analysis of
  traces of paints, textile fibers, cosmetics,
  explosives etc.

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Forensic applications

• E.g. hit-and-run crimes in traffic

Who was that _at_ idiot with some white car
in the parking place?!!
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Forensic applications
Py-GC of paint flake samples
Evidence
Suspect A
Suspect B
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THANK YOU ALL!!
Be careful in the traffic and especially on the
sea today...