By: Ben King

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

What is Pyrolysis?

http://www.csam.montclair.edu/earth/eesweb/imageU90.JPG

Auto sampler

pyrolyzer

Pyrolysis controller

Heated transfer line

GCMS

Py-GC/MS

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

How Does it Work?

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

Sample Preparation

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

The Three Pyrolyzers

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

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 Design

http://www.sge.com/uploads/lh/_0/lh_0zRR1NSHibbVkFiPo4A/pyrojector.jpg

Furnace Pyrolyzer

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 Sample Introduction

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 Temperature Control

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 Advantages

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

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

Furnace Pyrolyzer Disadvantages

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

Heated Filament Pyrolyzer

Analytix Ltd

Resistively Heated Filament Pyrolyzer

Fischer America

Curie Point Pyrolyzer

Filament Pyrolyzer Examples

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

Inductively Heated Filament: Curie-pt Pyrolyzer

Reference 13

Inductive Heating Characteristics of Alloys

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 Design

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 Design

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

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 Pyrolyzer Sample Introduction

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 Pyrolzer: Temperature Control

Self-limiting temperature Rapid heating No temperature calibration to perform Can prepare several samples and store Can be automated b/c no connections to wire-

simple 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 Advantages

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

Curie-pt Disadvantages

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 Pyrolysis

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: Design

Resistively Heated Filament Diagram

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: Sample Preparation

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: Interfacing

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/secReference 2

Resistively Heated Filament: Temperature Control

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: Advantages

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 increasesReference 2

Resistively Heated Filament: Disadvantages

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

Slow-rate Pyrolysis

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

Indirect◦ A trap is connected to pyrolyzer and is later

connected to analytical device

Reference 2

Direct/Indirect Transfer of Pyrolyzate to Detectors

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

Reproducibility of Pyrolysis

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

Increasing Reproducibility by Homogeneity

Study of compositional determination of styrene-methacrylate using Py-GC and H NMR◦ Standard deviation: 1-2% compared to 1% for NMR

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

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

Accuracy of Pyrolysis

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

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

Precision of Pyrolysis

Sample amount◦ Milligrams or micrograms

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

Sample Amount and Selectivity

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

Sensitivity of Pyrolysis

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

Detection Limit and Quantification Limit of Pyrolysis

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

Application of Pyrolysis

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-3-methoxycatechol, and 5-propenyl-3-methoxycatechol were detected.

Compounds arise from the pyrolysis of 5-hydroxyguaiacyl lignin moieties

Only the first one ever really detected, the other two rarely until using pyrolysis-GC/MS technique

Reference 6

Presence of 5-hydroxyguaicyl as Unit Native in Lignin

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

S/G-4.9 Efficiency of pulping directly

proportional to amount of syringyl units in lignin due to easy delignification of S-lignin◦ 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

Determination of Abaca Fiber Composition for Paper Pulping

syringyl

guaiacyl

Pyrogram of Abaca

Reference 4

Reference 4

Composition of Abaca Fibers

Composition of Abaca Fibers

Reference 4

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/GReference 11

Determination of Kenaf Fiber Composition for Paper Pulping

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

KL recovered from the laccase shows a lower degree of oxidation, accompanied by a substantial polymerization.◦ Used for commodity and specialty markets

Reference 3

Early Detection of Fungal Attack on Industrial Pine Lignin

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 Grass Fiber Composition for Bio-oil Application

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 Tagasaste Fiber Composition for Paper Pulping

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 lignin-

derived 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 ligninReference 1

Determination of Lignin Contribution in soil-HA by Pyrolysis

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 (phenol-enriched barrier between infected and living).

Reference 17

Early Detection of Wood Decay by Lignin Composition

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

S/G Ratio of Three Wood Areas

Reference 17

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 Laccase-mediator 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 5-hyroxyguaiacyl Units as Native Lignin Constituents in Plants as Seen by Py-GC/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, 453-463.

[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. Pyrolysis-capillary 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.