Pyrolysis: Instrumentation and Application

By: Ben King
What is Pyrolysis?
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A technique that is used in the analysis of
natural and artificial polymers or
macromolecules
A sample is heated up (mainly in a inert
atmosphere or vacuum) to decomposition to
produce smaller units which are carried by a
gas such as helium to the next instrument for
characterization.
Pyrolyzer is usually linked to a GC and a
detector such as MS or FTIR.
Reference 16, 2
Py-GC/MS
Auto sampler
Heated transfer
line
MS
GC
Pyrolysis
controller
pyrolyzer
http://www.csam.montclair.edu/earth/eesweb/imageU90.JPG
How Does it Work?
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Use either one of three pyrolysis designs:
Isothermal furnace, Curie Point filament
(inductively heated), and resistively heated
filament.
Sample heated to a pyrolysis temperature
slowly or rapidly and held for a few seconds.
Cleavage of chemical bonds within the
macromolecular structure producing low
molecular weight, more volatile chemical
moieties that are specific units of a particular
macromolecule.
Reference 16,2
Sample Preparation
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Normally no sample preparation is powdered or
particulate materials
Some samples require an extraction with an organic
solvent to remove any low molecular mass
components.
Some solid samples need to be dissolved in solvents
or ground up.
Amount of sample preparation depends on type of
polymer and how homogeneous the sample is.
Methylating reagents, which increase the volatility of
polar fragments, can be added to a sample before
pyrolysis.
◦ Tetramethylammonium hydroxide (TMAH) and trimethyl
sulfonium hydroxide (TMSH)
Reference 16, 2
The Three Pyrolyzers
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Each type can give reproducible results for
small samples
Furnace and resistively heated filament
pyrolyzers can be used for slow heating or
rapid heating.
Curie Point is used only in rapid heating
mode
Selectivity depends on personal preference,
experimental requirements, budget, or
availability
Reference 2
Furnace Pyrolyzer
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Small mount on the
inlet of GC
The metal or quartz
sample tube is wrapped
with heating wire and
thermally insulated
The furnace pyrolyzer
has a much larger
sample chamber than
the filament pyrolyzers
as seen in the figure.
Reference 2
Furnace Pyrolyzer Design
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Carrier gas enters from top or front to sweep
past sample inlet (carrying of the pyrolyzate)
before moving then directly into injection
port of chromatograph
Temperature is stabilized to within ±10 °C of
the desired temperature setpoint.
Thermocouple or resistance thermometer
used to indicate wall temperature
Reference 2
Furnace Pyrolyzer
http://www.sge.com/uploads/lh/_0/lh_0zRR1NSHibbVkFi
Po4A/pyrojector.jpg
Furnace Pyrolyzer Sample Introduction
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Can’ t usually admit air during sample
introduction due to GC
Heat rate dependent on sample material and
composition of sample introduction device
Liquid samples are injected by a syringe.
Solids are dissolved and injected, or injected
using a solid injecting syringe
A cool chamber is used to load samples into a
crucible which is lowered into hot zone.
Reference 2
Furnace Pyrolyzer Temperature Control
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Resistive heating element is around the
central tube of furnace
Temperature is monitored by sensor with
data feedback to the controller for
adjustments of thermal energy.
Temperature control also depends on size
and mass of sample, and residence time
inside furnace.
Reference 2
Furnace Pyrolyzer Advantages
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Inexpensive and relatively easy to use
Isothermal heating, with no heating ramp rate
or pyrolyis time unless that is the intention.
Liquid and gas pyrolysis is more easily
achieved than with filament type.
Reference 2
Furnace Pyrolyzer Disadvantages
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Since the tube is considerably larger than
sample, temperature control is more difficult
to achieve
Large volume for sample to pass through to
get to analytical device
Excessively low carrier gas flow may lead to
secondary pyrolysis
Temperature stability depends on sample
size, nature, and geometry
Reference 2
Furnace Pyrolyzer Disadvantages
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Metal systems, initial pyrolysis may produce
smaller organic fragments which encounter
hot surface of tube and undergo secondary
rxns
Generally necessitating split capillary analysis
Has longer retention times, broad peak
shapes, and interference peaks.
Reference 2, 13
Heated Filament Pyrolyzer
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Sample placed directly onto cold heater then rapidly heated to
pyrolysis temperature
Two Methods:
◦ resistance-controlled current is passed through heating
filament
◦ Inductive- current is induced into heating filament which is
made of ferromagnetic metal
Sample size limited to an amount compatible with mass of
filament. (low to high microgram range)
A sample must also be compatible for the analytical devices
that are linked up to the pyrolyzers.
◦ GC, FTIR, ICP, MS, etc.
Reference 2
Filament Pyrolyzer Examples
Fischer America
Analytix Ltd
Curie Point Pyrolyzer
Resistively Heated Filament
Pyrolyzer
Inductively Heated Filament: Curie-pt
Pyrolyzer
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Electrical current induced onto a wire made of
ferromagnetic metal by use of magnet or high
frequency coil
Continual induction of current wire will begin to
heat until it reaches a temperature at which it is
no longer ferromagnetic
Becomes paramagnetic, no further current may
be induced in it.
Heated to pyrolysis temperature in milliseconds
Reference 2
Inductive Heating Characteristics of
Alloys
Reference 13
Curie-pt Design
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Insertion:
Pyrolysis chamber which is surrounded by coil, is
opened and sample wire is dropped or place inside
Sample wire is attached to a probe which is inserted
through a septum into the chamber which is
surrounded by the coil
Reference 2, 13
Curie-pt Pyrolyzer Design
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Chamber can be attached directly to part of
GC or isolated from GC by valve
Allows for autosampling and for loading
wires into glass tubes for sampling and
inserting into coil zone.
Controls for parameters of pyrolysis wire and
also temp selection for interface chamber
housing the wire.
Reference 2, 13
Curie-pt Pyrolyzer Sample Introduction
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Sample and wire kept to low mass
Samples either coated onto filament as very thin
layer
Soluble materials dissolved in appropriate solvent
and wire dipped into.
◦ Solvent dries and leaves thin deposit
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Non-soluble:
◦ finely ground samples maybe deposited onto wire from a
suspension which is dried to leave coating of particles
◦ Applied as melt
◦ Create a trough with wire
◦ Bend or crimp wire around material
◦ Encapsulate sample with foil of ferromagnetic material
and dropped into high frequency cell chamber.
Reference 2
Curie-pt Pyrolzer: Temperature Control
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Pyrolysis temperature is determined by the
composition of the ferromagnetic material
Reproducible and accurate temp control
depends on accuracy of wire alloy, power of
coil, and placement of wire into system
Use the same manufacturer, same sample
loading, and placement to minimize variation
of sample results
Reference 2, 13
Curie-pt Advantages
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Self-limiting temperature
Rapid heating
No temperature calibration to perform
Can prepare several samples and store
Can be automated b/c no connections to wiresimple insertion
Can either clean and reuse wire or discard
Gives sharper characteristic peaks than furnace
type
Demonstrates constant pyrolysis product
composition yield even with sample weight
increases
Good heat transfer
Reference 2, 13
Curie-pt Disadvantages
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Limited temperatures to choose
Harder to optimize pyrolysis temperature
Concerns of catalytic effect of metals on very
small samples.
Range of temps 350 - 1000°C (10 - 20
specific alloys )
Can’t have linear heating
Reference 2
Resistively Heated Filament Pyrolysis
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Heat from ambient to pyrolysis temperature
quickly also with small samples
Current supplied is connected directly to
filament
A filament made of material with high
electrical resistance and wide operating
range. (Ex: Fe, platinum, and nichrome
Reference 2
Resistively Heated Filament: Design
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Sample placed onto pyrolysis filament which is
then inserted into the interface housing and
sealed to insure flow to column.
Flat strip, foil, wire, grooved strip, or coil.
Coil- tube or boat inserted into filament, like
very small rapidly heating furnace
Must be connected to controller capable of
supplying enough current to heat filament rapidly
with some control or limit
Temperature measured by resistance of material
or by external measure such as optical pyrometry
or thermocouple.
Reference 2
Resistively Heated Filament Diagram
Resistively Heated Filament: Sample
Preparation
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Solution applied to filament by syringe
Powder solids use small quartz tubes which is
inserted into coiled filament
Place in tube, held in position using plugs of
quartz wool, weighed, and inserted into coiled
element.
Rise and final temp different then directly on
filament
Not used for soils, ground rock, textiles, and
small fragments of paint
Viscous liquid applied on surface of filament or
suspended on surface of filler material.
Reference 2
Resistively Heated Filament: Interfacing
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Can be easily interfaced with other analytical
devices as long the filament is positioned
right and the probe is sealed off from air.
Need a heated interface between pyrolyzer
and column
Interface has its own heater to prevent
condensation of pyrolyzate compounds and
should have minimal volume
Valve needed between pyrolyzer and column
so insertion or removal of filament can be
done.
Reference 2
Resistively Heated Filament:
Temperature Control
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Temperature is related to current passing
through it
Conditions have to be very similar for good
reproducibility
Computers control and monitor filament temp,
control voltage used and adjusted for changes in
resistance
Use photodiode to read actual temp of filament
Can select any final pyrolysis temp and any
desired rate
Can heat as slow as .01 °C/min and as rapidly as
30000 °C/sec
Reference 2
Resistively Heated Filament: Advantages
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Can measure how materials are affected by
slow heating (TGA)
Permits interface of spectroscopic techniques
with constant scanning for 3d, time-resolved
thermal processing.
Can be inserted directly into ion source of MS
or light path of FTIR
Products monitored in real time throughout
heat process.
Reference 2
Resistively Heated Filament:
Disadvantages
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Can’t automate process since multiple samples
need same filament and multiple filaments need
same instrument
Any damage or alteration to the resistance of
part of the loop will have an effect on actual
temp produced by controller.
Introduction of some samples into heated
chamber before pyrolysis may produce
volatilization or denaturation, altering nature of
sample before degradation.
Not good heat transfer
Yields can decrease as sample weight increases
Reference 2
Slow-rate Pyrolysis
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Related to TGA, multiple step degradation
Gives time-resolved picture of production of
specific products
Programmable furnace and resistively heated
filament
50-100 °C/min to extract organics
Reference 2
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Direct/Indirect Transfer of Pyrolyzate to
Detectors
Direct
◦ Collection directly onto GC, at ambient or
subambient conditions
◦ Direct to MS or FTIR
◦ Pyrolyzer inserted into an expansion chamber,
which flushed or leaked into spectrometer, or the
pyrolyzer is inserted directly into instrument
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Indirect
◦ A trap is connected to pyrolyzer and is later
connected to analytical device
Reference 2
Reproducibility of Pyrolysis
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Sources of error- size and shape,
homogeneity, and contamination of sample
For polymers, need to make same size and
shape samples
Overloading affects rate at which sample
heats (thickness of material- thermal
gradient)
10-50 microgram samples desirable for
direct pyrolysis to GC and twice that for FTIR
Reference 2
Increasing Reproducibility by
Homogeneity
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Ground up material under cryogenic
conditions
Chop sample finely using scalpel and then
analyze small fragments together
Made into solution
Bigger samples of .1mg
Use a split mode GC injection with a large
split ratio to avoid signal saturations
Pass pyrolyzate in carrier gas through small
sample loop attached to a valve which is
interfaced to analytical unit. (clean run to run)
Reference 2
Accuracy of Pyrolysis
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Study of compositional determination of
styrene-methacrylate using Py-GC and H
NMR
◦ Standard deviation: 1-2% compared to 1% for NMR
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Accuracy effected by pyrolysis temp rise time,
sample size, sample surface area, and sample
thickness
Small sample size, little sample prep, rapid
turnaround time, relatively inexpensive, easily
operable, and can be automated
Reference 8
Accuracy of Pyrolysis
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550-650 °C yielded reproducible
fragmentation
Difference between NMR and GC pyrolysis
results are in the range of 0-4% and 0-4.8%
for styrene/n-butyl methacrylate and
styrene/methyl methacrylate
Standard deviation for py-GC was from 1.2 to
2.1 %
Reference 8
Precision of Pyrolysis
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Evaluating Emission of various materials for PAH’s
released (Py-GC/MS)
◦ Pyrolyzed at 1000 °C for 60 sec (resistively heated)
◦ RSD from 7.5% (1-methyl naphthalene) to 18%
(acenaphtene)
◦ Most abundant species RSD less than or equal to
15% , less abundant much higher
Increase of precision and repeatability if using offline
system
Shows good repeatability, limit of quantification, and
linearity
Reasonably good for properly evaluating the quantity
of PAHs emitted from different kinds of materials.
Reference 9
Precision of Pyrolysis
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Investigation of Food Stuffs (Py-Elemental
Analysis)
◦ 65 Foods analyzed
◦ RSD from 1 to 13% for Carbohydrates in each one of
the samples that also contained protein, fats, and
dietary fibers
Reference 7
Sample Amount and Selectivity
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Sample amount
◦ Milligrams or micrograms
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Selectivity
◦ Cellulose
 Altering heating conditions improve selectivity
◦ Sample vs Standards of PVC, PS, SB, PMMA, and PC
mixture
 All main marker compounds very similar
 Naphthalene peak of polymer mixture 96% recovered
relative to standards
Reference 15
Sensitivity of Pyrolysis
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Volatile elements
◦ Slurries- high sensitivity for pyrolysis temp < 400 °C,
decrease from 400-800 °C
◦ Aqueous and digested standards sensitivity plateaus across
temps
◦ Digested better sensitivity than aqueous 15% (As) & 65% (Pb)
◦ High sensitivity obtained for As is obviously related to the
presence of carbon in the plasma and increase sensitivity at
low pyrolysis temp is in agreement with above-discussed
charge-transfer mechanism.
◦ Using modifiers Pd/Mg or raising concentrations of organics
raises sensitivity at low temps.
◦ Sensitivity changes due to differences in analyte transport
from the ETV to the ICP produced by carrier effects and/or
changes in analyte ionization in the plasma.
Reference 14
Detection Limit and Quantification Limit of
Pyrolysis
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Detection Limit is dependent on analytical device
it is attached to
GC’ s detection limit
Can be as low as ng or pg
Analysis of polymer mixture Py - ETV - ICP - MS
Limit of Quantification
500ng, 10 mg / kg dry mass
Limit of Detection
150ng,
S/N=3
Linearity in a range from .5 to 100 microgram
Reference 15
Application of Pyrolysis
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Pyrolysis can be applied to the analysis of
many natural and artificial macromolecules
Natural: lignin, cellulose, chitin, etc
Artificial: PVC, acrylics, varnishes, etc
Can be used for applications similar to TGA
Used in several specific areas as well
Presence of 5-hydroxyguaicyl as Unit
Native in Lignin
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Lignin content was estimated by the Klasan
method
Curie-pt pyrolyzer, pyrolysis temp- 610 °C
Fibers were finely ground to sawdust
In samples of eucalypt, abaca, and kenaf,
compounds 3-methoxycatechol, 5-vinyl-3methoxycatechol, and 5-propenyl-3methoxycatechol were detected.
Compounds arise from the pyrolysis of 5hydroxyguaiacyl lignin moieties
Only the first one ever really detected, the other
two rarely until using pyrolysis-GC/MS technique
Reference 6
Determination of Abaca Fiber
Composition for Paper Pulping
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Nonwoody source for paper for developing
countries
Curie-pt pyrolyzer, pyrolysis temp-610 °C
Pyrolysis in presence of tetramethylammonium
hydroxide (prevents decarboxylation)
Abaca fiber is 13.2% lignin
Main compounds of lignin are p-hydroxyphenyl
(H), guaiacyl (G),and syringyl (S)
Reference 4
Determination of Abaca Fiber
Composition for Paper Pulping
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S/G-4.9
Efficiency of pulping directly proportional to
amount of syringyl units in lignin due to easy
delignification of S-lignin
syringyl
◦ S-lignin is mainly linked by a more labile ether bond
◦ S-lignin is relatively unbranched
◦ S-lignin is lower condensation degree than the G lignin
Reference 4
guaiacyl
Pyrogram of Abaca
Reference 4
Composition of Abaca Fibers
Reference 4
Composition of Abaca Fibers
Reference 4
Determination of Kenaf Fiber
Composition for Paper Pulping
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Kenaf alternative raw material for pulp b/c
renewable, inexpensive, and grown easily
Pyrolysis-GC/MS in presence of TMAH
Curie-pt pyrolyzer, pyrolyzed at 500 °C for 4
sec
Tried offline pyrolysis and low-temp pyrolysis
250 °C for 30 min
Chinpi-3: core 1.53 S/G and bast 3.42 S/G
Similar results of wet chemical method core
1.87 S/G and bast 4.71 S/G
Reference 11
Early Detection of Fungal Attack on
Industrial Pine Lignin
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Double-shot pyrolyzer, pyrolysis at 500 °C
Samples treated with laccase and others with laccase-mediator system
Py-GC/MS showed a decrease in phenolic and methoxy-bearing
pyrolysis products during the onset of incubation.
Immediately, a 22% decrease in the total phenolic lignin content,
increase in aldehyde (64%), ketone (50%), and acid groups (.21%).
After 48 hrs, 10% decrease in lignin, 10% guaiacyl units, 1% syringyl
units, 10% decrease in ethyl phenolic derivatives
Klason Lignin (KL) recovered from the laccase-mediator system (LMS)
after 48hrs of incubation shows high degree of oxidation and
depolymerization
◦ Desirable for industrial applications
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KL recovered from the laccase shows a lower degree of oxidation,
accompanied by a substantial polymerization.
◦ Used for commodity and specialty markets
Reference 3
Determination of Grass Fiber
Composition for Bio-oil Application
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15 Lolium and Festuca grasses
Speculated by researchers that reduce lignin
content will produce a more stable bio-oil by
reducing the chances of phase separation by
improving solubility, stability, and homogeneity
Pyrolysis by inductive heated coil, pyrolysis at
600 °C, .4 °C/ms
Wet chemistry- grass leaves contained 2.14 to
3.72% lignin
Abundances of key markers of lignin added up by
py-GC/MS were correlated to the amount of
Klason Lignin in each grass.
Reference 10
Determination of Tagasaste Fiber
Composition for Paper Pulping
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Found in Canary islands, Australia, and New
Zealand
Usefulness for paper pulp production
Microfurnace pyrolyzer, pyrolysis temp- 500
°C, 20 °C/min
18.9% lignin
S/G 1.6
Reference 12
Determination of Lignin Contribution in
soil-HA by Pyrolysis
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Lignin contribution to the soil Humic Acid (HA) from
maize plants
Curie-pt pyrolyzer, 600 °C for 5 sec
Pyrolysate of maize plant was dominated by ligninderived products
Py-GC/MS determined HA derived from plants was
composed of aromatic compound derived mainly for
lignin had a high S/G ratio.
Hemp and flax showed a predominance of guaiacyl
Jute, sisal, and abaca showed a predominance of
syringyl
P-hydroxycinnamic acids, namely p-coumaric and
ferulic acids, are also found in isolated lignin
Reference 1
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Early Detection of Wood Decay by Lignin
Composition
Furnace pyrolyzer
Characterization of internal wood
degradation of London-plane tree (early
detection of white rot fungal infection by
lignin degradation before cavity formation)
Use pyrolysis product composition syringyl/guaiacyl ratio
Samples from sound wood, extensively
degraded wood, and R-zone (phenolenriched barrier between infected and living).
Reference 17
S/G Ratio of Three Wood Areas
Area of Wood
Disk A
Disk B
Sound (S/G)
1.61
1.51
R-zone (S/G)
1.39
1.28
Rotten (S/G)
1.12
1.1
Reference 17
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Pyrolysis is a technique that has endless
possibilities for polymer or macromolecule
analysis.
It can give reproducible results with good
precision and with short amount of time
Py-GC/MS can be used extensively for
analysis of lignins in the composition of
plants and can be a great tool for the paper
industry and biofuel industry.
[1]Adani, Fabrizio; Spagnol, Manuela; Nierop, Klaas G. J. Biochemical Origin
and Refractory Properties of Humic Acid Extracted From Maize Plants: the
Contribution of Lignin. Biochem. 2007, 82, 55-65.
[2]Applied Pyrolysis Handbook, Wampler Thomas P., Ed. ; M. Dekker: New
York, 1995.
[3]Arzola, K. Gonzalez; Polvillo, O.; Arias, M. E.; Perestelo, F.; Carnicero, A.;
Gonzalez-Vila, F. J. ; Falcon, M. A. Early Attack and Subsequent Changes
Produced in an Industrial Lignin by a Fungal Laccase and a Laccasemediator System: an Analytical Approach. Appl. Microbiol. Biotechnol. 2006,
73, 141-150.
[4]Del Rio, Jose C. ; Gutierrez, Ana. Chemical Composition of Abaca (Musa
textilis) Leaf Fibers Used for Manufacturing of High Quality Paper Pulps. J.
Agric. Food Chem. 2006, 54, 4600-4610.
[5]Del Rio, Jose C. ; Gutierrez, Ana; Rodriguez, Isabel M.; Ibarra, David;
Martinez, Angel T. Composition of Non-woody Plant Lignins and Cinnamic
Acids by Py-GC/MS, Py/TMAH and FTIR. J. Anal. Appl. Pyrolysis 2007, 79,
39-46.
[6]Del Rio, Jose C. ; Martinez, Angel T. ; Gutierrez, Ana. Presence of 5hyroxyguaiacyl Units as Native Lignin Constituents in Plants as Seen by PyGC/MS. J. Anal. Appl. Pyrolysis 2007, 79, 33-38.
[7] Dennis, M. J.; Heaton K.; Rhodes, C.; Kelly, S.D.; Hird, S.; Brereton, P.A.
Investigation Into The Use of Pyrolysis-elemental Analysis for the
Measurement of Carbohydrates in Food Stuffs. Analytica Chimica Acta 2006,
555, 175-180.
[8]Evans, Donald L.; Weaver, Judith L.; Mukherji, Anil K.; Beatty, Charles L.
Compositional Determination of Styrene-Methacrylate Copolymers by
Pyrolysis Gas Chromatography, Proton-Nuclear Magnetic Resonance
Spectrometry, and Carbon Analysis. Anal.Chem. 1978, 50, 857-860.
[9]Fabbri, Daniele; Vassura, Ivano. Evaluating Emission Levels of Polycyclic
Aromatic Hydrocarbons From Organic Materials by Analytical Pyrolysis. J.
Anal. Appl. Pyrolysis 2006, 75, 150-158.
[10]Fahmi, R.; Bridgwater, A.V.; Thain, S.C.; Donnison, I. S.; Morris P. M.; Yates
N. Prediction of Klason Lignin and Lignin Thermal Degradation Products by
Py-GC/MS in a Collection of Lolium and Festuca Grasses. J. Anal. Appl.
Pyrolysis, 2007, 80, 16-23.
[11]Kuroda, Ken-ichi; Izumi, Akiko; Mazumder, Bibhuti B.; Ohtani, Yoshito;
Sameshima, Kazuhiko. Characterization of Kenaf (Hibiscus Cannabinus)
Lignin by Pyrolysis-Gas Chromatography-Mass Spectometry in the Presence
of Tetramethylammonium Hydroxide. J. Anal. Appl. Pyrolysis 2002, 64, 453463.
[12]Marques, Gisela; Gutierrez, Ana; Del Rio, Jose C. Chemical Composition of
Lignin and Lipids from Tagasaste (Chamaecytisus Proliferus Spp. Palmensis).
Indust. Crops Prod. 2008, 28, 29-36
[13] Oguri, Naoki; Kirn, Poongzag. Design and Applications of a Curie Point
Pirolyzer.
[14] Silva, A. F.; Welz, B.; De Loos-Vollebregt, M.T.C. Evaluation of Pyrolysis
Curves for Volatile Elements in Aqueous Standards and Carbon-Containing
Matrices in Electrochemical Vaporization Inductively Coupled Plasma Mass
Spectrometry. Spectrochimica Acta B. 2008, 63, 755-762.
[15] Tienpont, Bart; David Frank; Vanwalleghem, Freddy; Sandra, Pat. Pyrolysiscapillary Gas Chromatography-Mass Spectometry for the Determination of
Polyvinyl Chloride Traces in Solid Environmental Samples. J. Chromatography
A. 2001, 911, 235-247.
[16] University of Bristol. Pyrolysis Gas Chromatography Mass Spectrometry.
http://www.bris.ac.uk/nerclsmsf/techniques/pyro.html (Accessed Apr. 27,
2005)
[17] Vinciguerra, Vitterio; Napoli, Aldo; Bistoni, Angela; Petrucci, Gianluca;
Sgherzi, Rocco. Wood Decay Characterization of a Naturally Infected London
Plane-tree in Urban Environment Using Py-GC/MS. J. Anal. Appl. Pyrolysis
2007, 78, 228-231.
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Incendiary weapons

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