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Title: ANALYTICAL PYROLYSIS


1
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
2
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?

3
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
4
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)
5
Analytical instrumentation
  • Typical on-line analytical instrumentation
    includes

1. Helium source 2. Pyrolysis equipment 3. Gas
chromatograph 4. Mass spectrometry 5. Data
handling
6
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

7
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
8
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

9
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

10
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

11
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
12
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.

13
Forensic applications
  • E.g. hit-and-run crimes in traffic

Who was that _at_ idiot with some white car
in the parking place?!!
14
Forensic applications
Py-GC of paint flake samples
Evidence
Suspect A
Suspect B
15
THANK YOU ALL!!
Be careful in the traffic and especially on the
sea today...
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