THERMOGRAVIMETRIC ANALISYS SDT 650

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Thermogravimetric Analysis (TGA)
Theory and Applications
Presented by Kadine Mohomed, Ph. D
Applications Manager
TA Instruments – Waters LLC
© TA Instruments
1

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TGA: Theory and Applications
Part 1
2
What is TGA?
Calibration and verification
Instrument hardware
Experimental design

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Part 2
3
General Applications
Improving Resolution
Kinetics and Activation Energy
Evolve Gas Analysis

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What is Thermogravimetric Analysis (TGA)?
•Thermogravimetric Analysis
(TGA) measures weight/mass
change (loss or gain) and the rate
of weight change as a function of
temperature, time and
atmosphere.
•Measurements are used primarily
to determine the composition of
materials and to predict their
thermal stability. The technique
can characterize materials that
exhibit weight loss or gain due to
sorption/desorption of volatiles,
decomposition, oxidation and
reduction.
4

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What TGA Can Tell You
5
•Thermal Stability of Materials
•Oxidative Stability of Materials
•Composition of Multi-component Systems
•Estimated Lifetime of a Product
•Decomposition Kinetics of Materials
•The Effect of Reactive or Corrosive Atmospheres
on Materials
•Moisture and Volatiles Content of Materials

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Mechanisms of Weight Change in TGA
6
•Weight Loss:
Decomposition: The breaking apart of chemical bonds.
Evaporation: The loss of volatiles with elevated
temperature.
Reduction: Interaction of sample to a reducing atmosphere
(hydrogen, ammonia, etc.).
Desorption.
•Weight Gain:
Oxidation: Interaction of the sample with an oxidizing
atmosphere.
Absorption.
All of these are kinetic processes (i.e. there is a rate at which
they occur).

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Thermal Stability of Polymers
1: Gas 1 (N2)
2: Ramp 20ºC/min to 650ºC
3: Gas 2 (air)
Gas Switch
7

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Oxidative Stability (Polypropylene)
431.95°
C
285.40°
C
0
20
40
60
80
100
120
Weight
(%)
0 200 400 600 800 1000
Temperature (°
C)
PP Resin Nitrogen
–––––––
PP Resin Air
– – – –
Universal V4.3A TA Instruments
8

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TGA of Drug A Monohydrate
9
4.946%
(0.7505mg)
-2
0
2
4
6
Deriv.
Weight
(%/min)
80
85
90
95
100
105
Weight
(%)
0 50 100 150 200 250 300
Temperature (°
C) Universal V3.4C TA Instruments
Sample: Drug A Monohydrate
Size: 15.1740mg
Heating Rate: 10°
C/min
Water weight loss
Decomposition

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TGA Data Shows That Acetylsalicylic Acid is
Decomposing Prior to Apparent Melting Point
10

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400 450 500 550 600
0
200
400
600
800
1,000
-10
10
30
50
70
90
110
Temperature (°
C)
Activation
Energy
(kJ/mol)
[
]
Weight
(%)
Polytetrafluoroethylene
Modulated TGA – Decomposition Activation
Energy and Lifetime Kinetics
11

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TA Instruments TGA Models
12

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TGA 5500 Discovery TGA Q500/50
Temperature Range Ambient to
1200°
C
Ambient to
1200°
C
Ambient to
1000°
C
Isothermal Temperature
Accuracy
±1°
C ±1°
C ±1°
C
Heating Rate Range 0.1 to 500°
C/min
(Linear)
1600°
C/min
(Ballistic)
0.1 to 500°
C/min
(Linear)
1600°
C/min
(Ballistic)
0.1 to 100°
C/min
(Linear)
Sample Weight
Capacity
1000mg 750 mg 1000 mg
Dynamic Weighing
Range
1000mg 100 mg 1000 mg
Baseline Dynamic Drift
(50-1000°
C)
10 µg 10 µg 50 µg
Discovery TGA and Q500/50 Specifications
13

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Thermogravimetric Analyzers
•A TGA must accurately:
control heating rate (furnace)
measure the change in temperature (thermocouple)
measure the mass of a sample and the change in mass as it is
heated or held at an isothermal temperature (balance)
14

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TGA: Schematic Diagram
15
Photodiodes
Infrared LED
Meter movement
Balance arm
Tare pan
Sample platform
Thermocouple
Sample pan
Furnace assembly
Purge gas outlet
Heater
Elevator base
Purge gas inlet
Sample pan holder

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TGA Balance and Operation
16
• The balance operates on a
null-balance principle. At the
zero, or “null” position equal
amounts of light shine on the
2 photodiodes.
• If the balance moves out of
the null position an unequal
amount of light shines on the
2 photodiodes.
• Current is then applied to the
meter movement to return the
balance to the null position.
• The amount of current
applied is proportional to the
weight loss or gain.

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TGA Furnace Options
17

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TGA Calibration and Verification
•A TGA measures the change in mass of a material with respect to
temperature, time and atmosphere.
•A TGA is calibrated for mass (user), temperature (user) and gas flow
rate control (manufacturer).
•A calibration is affected by
Purge gas and flow rate
Type of specimen pan
Heating rates
18

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International Standards
19
•American Society of Testing and Materials, ASTM
www.astm.org
•International Organization of Standards, ISO
www.iso.org
•Deutsches Institut für Normung/German Institute for Standardization,
DIN
www.din.de/en

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ASTM/ISO Standards for TGA Temperature and
Mass/Weight Calibration
20
•ASTM E 1582 - Standard Practice for Calibration of Temperature
Scale for Thermogravimetry
•ASTM E 2040 - Standard Test Method for Mass Scale Calibration of
•ISO 11358 – Thermogravimetry (TG) of Polymers

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Requirements Prior to Calibration
21
•The TGA pan should be cleaned prior to calibration procedures. If
using platinum or alumina pans, a flame torch can be used to burn off
organic residue.
•The purge gas flow rate setting should be set (flow rates differ
depending on furnace design and internal volume). The flow rate
should not deviate by more than +/- 5ml/min.
•Use high purity reference materials for calibration

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ASTM E 2040 - Mass Scale Calibration of
22
•The mass signal generated by a TGA is compared to the mass of a
reference material traceable to a national reference laboratory. A linear
correlation using two calibration points is used to relate the mass (or
weight) signal generated by the TGA and that of the reference
material.
• This test method calibrates or demonstrates conformity of
thermogravimetric apparatus at ambient conditions. Most
thermogravimetry analysis experiments are carried out under
temperature ramp conditions or at isothermal temperatures distant
from ambient conditions. This test method does not address the
temperature effects on mass calibration.
•TA Instruments uses a zero tare, then a 100mg and 1000mg mass
standard to calibrate the TGA.

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Calibration – Weight (Manual)
23
Enter the mass of the calibration
weight

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Simply reload the mass to verify – mass
difference of ~ 0.005%

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Discovery TGA 5500 Baseline Performance
26

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Q 500/50 Baseline Performance
27
26.87µg
Q500 TGA w/ EGA Furnace @ 20°C/min
Using Recommended Flowrates
Sample Purge 90ml/min of He
Balance Purge 90ml/min of He
60
70
80
90
Sample
Purge
Flow
(mL/min)
0
10
20
30
40
50
Balance
Purge
Flow
(mL/min)
-20
-10
0
10
20
Weight
(µg)
0 200 400 600 800 1000
Temperature (°C)

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ASTM E 1582 - Calibration of Temperature
Scale for Thermogravimetry
28
•The standard describes two methods by which the TGA can be
calibrated for temperature; by melting point or magnetic transition.
The most common approach for a TGA would be the magnetic
transition approach.
•Curie Point Temperature - that temperature where the material loses
its magnetic susceptibility - defined as offset point.
•Paramagnetic - a material that is susceptible to attraction by a magnet
•Temperature Calibration points are determined by comparing the
measured melting onset temperature to the literature value
•TA Instruments software allows for up to 5 temperature calibration
points
Generally, these should bracket the temperature range of interest
for subsequent samples

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TGA: Temperature Calibration
Magnet
Vertical Balance Configuration
Sample
Tare
Attraction of Magnetic Sample to Magnet Results
in Initial Weight Gain, which is lost at the Curie
Transition Temperature
%
temp
Offset
29

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Curie Temperature Reference Materials
30
•International Confederation for Thermal Analysis and
Calorimetry (ICTAC) developed a set of six certified and
traceable Curie temperature reference materials for the
calibration of TGA and SDT.
•The set consists of Alumel®, nickel, cobalt and three
cobalt/nickel alloys.
•The materials permit temperature calibration in about 200 °
C
intervals over the range of 150 to 1120 °
C.
•TA Instruments is the exclusive worldwide distributor for
these certified and traceable Curie point materials.

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Reference Products for TGA
31
Curie Temperature Reference Materials
TA Instruments is the exclusive worldwide distributor for a
set of six certified and traceable Curie temperature
materials developed by ICTAC.
Six curie point standards are available
Alumel 153°
C
Nickel 358C
Ni83Co17 555°
C
Ni63Co37 747°
C
Ni37Co63 931°
C
Cobalt 1116.0°
C

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Curie Standards with ICTAC traceability
32

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Calibration – Choose Calibrant, Method is
Automatically Generated
33

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TGA – Temperature Calibration
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TGA – Temperature Verification
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Calibration – Standard Reference Materials
36
•Should I expect to obtain the same uncertainty values
observed by the certifying agency?
•Not necessarily!
•What should my uncertainty value be? Where do I start?
•A good place is the precision and bias section associated
with the ASTM method for the analysis – in this case
ASTM E1582.
•ASTM Statement:

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How Often Do I Calibrate?
37
•Protocol is determined by your lab and needs, but there is
no substitute for sound analytical chemistry!
•You simply have to be confident that the data you provide
is correct.
•TA recommends verification on a regular basis.
•Verification is running a known reference material in the
standard operating mode and determining the Curie Point
for temperature and …
•Simply placing a known weight on a tared pan and
checking the mass measured by the balance.
•Control charts allow for statistical monitoring of instrument
performance.

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How Often Do I Calibrate? – The Case for
Control Charting
38
•Example:
Laboratory A has TA Instruments come in for a preventive maintenance
visit every January. This visit includes calibration of the temperature and
mass.
No further calibration or verification is performed until September of the
same year when an internal customer questions the data.
A check of the calibrations shows that the instrument is reading 20 °
C too
high and the mass 20 mg too low.
When did the calibration change?
With no verification protocol in place, all of the data for the previous 9
months is considered unreliable. Some protocols require that each client
be notified about the potential discrepancies in their data.
A weekly verification protocol and control chart maintenance would
minimize the amount of suspect data.
Verification of an alumel / nickel calibration takes about 20 minutes.
Verification of the mass calibration using the supplied differential masses
takes less than 10 minutes

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Calcium Oxalate “Standard” Analysis
39
•Although Calcium Oxalate is not generally accepted as a
“Standard Material,” it does have practical utility for
INTRA-laboratory use
•Carefully control the experimental conditions; i.e. pan type,
purge gases/flow rates, heating rate
•Particularly control the amount (~5mg) and the particle
size of the sample and how you position it in the pan
•Perform multiple runs, enough to do a statistical analysis
•Analyze the weight changes and peak temperatures and
establish the performance of YOU and YOUR instrument
•When performance issues come up, repeat the Calcium
Oxalate analysis

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Calcium Oxalate Decomposition
40
•1st Step CaC2O4
•H2O (s) CaC2O4 (s) + H2O (g)
Calcium Oxalate Monohydrate Calcium Oxalate
•2nd Step CaC2O4 (s) CaCO3 (s) + CO (g)
Calcium Oxalate Calcium Carbonate
•3rd Step CaCO3 (s) CaO (s) + CO2 (g)
Calcium Carbonate Calcium Oxide

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Calcium Oxalate Repeatability
41
0.0
0.6
[
–––––––
]
Deriv.
Weight
(%/°
C)
20
40
60
80
100
Weight
(%)
0 200 400 600 800
Temperature (°
C)
Overlay of 8 runs, same conditions

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Calcium Oxalate Repeatability
42
Transition 1 Transition 2 Transition 3
Wt Change Peak Temp Wt Change Peak Temp Wt Change Peak Temp
Run # % °
C % °
C % °
C
1 12.13 156.68 18.78 493.37 29.62 684.33
2 12.22 153.60 18.75 494.17 29.56 680.43
3 12.20 155.40 18.76 495.6 29.63 684.11
4 12.21 155.58 18.77 495.98 29.69 688.11
5 12.21 154.05 18.75 494.72 29.54 684.28
6 12.20 154.91 18.73 495.62 29.58 684.83
7 12.21 155.09 18.77 494.71 29.61 683.92
8 12.20 153.52 18.77 493.84 29.57 681.85
Ave 12.20 154.85 18.76 494.75 29.60 683.98
Std Dev 0.028 1.08 0.016 0.93 0.048 2.24
Theoretical 12.3 19.2 30.1
Accuracy 0.8% 2.3% 1.7%
Precision 0.2% 0.1% 0.2%

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Instrumental Considerations

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Instrument Hardware and Gas Selection
Considerations
44
Gas Delivery Module – Discovery TGAs
• Nitrogen - inert, inexpensive and readily available
• Helium - inert, commonly used when performing TGA-MS,
often provides best baseline but will make furnace work
harder at high temperature
• Air/Oxygen - used when studying oxidative stability of
materials, can sometimes improve resolution of weight
loss events
• Gas mixing for specific atmospheres – hydrogen, carbon
dioxide and other gases
TGA Heat Exchanger
• Check cleanliness (no algae growth) once every 3 months
• To clean: empty old water, fill with DI water and add
conditioner (algae growth suppressor) if available
• For Q series, after filling, in software choose “Control
Prime Exchanger”

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TGA: Purge Gas Plumbing
45
•Mass Flow Controllers
The gas 1 port purges both sample and balance areas. Gas
1 should be an inert gas (N2, He, Ar)
The gas 2 port is used when a different purge gas is
required or gas switching is used. Typically this is air or O2.
Gas type is assigned to Mass Flow Controller in the
Instrument section of the control software and chosen
before on the setup page.
Copper oxalate can be used to detect
any oxygen contamination

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Test for Oxygen Contamination of N2 Purge
Gas
46
10 minute Nitrogen pre-purge
-2
0
2
4
6
Deriv.
Weight
(%/°
C)
40
60
80
100
120
Weight
(%)
0 100 200 300 400 500 600
Temperature (°
C)
Instrument: TGA Q50 V6.7 Build 203
Copper Oxalate

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Effect of Oxygen on Copper Oxalate
47
3.561%
(0.4302mg)
10 minute Nitrogen pre-purge
No contamination
Excessive contamination
0.2791%
(0.02653mg)
6.839%
(0.9421mg)
35
40
45
50
55
60
65
Weight
(%)
200 300 400 500 600 700
Temperature (°C) Universal V4.4A TA Instruments

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Copper Oxalate – Large Mass
48
-20
0
20
40
60
80
Deriv.
Weight
(%/min)
40
60
80
100
Weight
(%)
0 100 200 300 400 500 600
Temperature (°
C)
Universal V3.3B TA Instruments
400 450 500 550
41.5
42.0
42.5
Size = 53mg
10 min prepurge

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Baseline Performance Verification
49
•A good way to quantify how well the TGA is working
•Especially important for measuring small weight losses
associated with volatilization or small amounts of residue
•Run clean, empty, tared pan, over temperature range of
interest, at desired heating rate
•Plot weight in µg vs. temperature
•Dynamic drift should be less than 10 micrograms for the
Discovery TGA, TGA 5500 and less than 50micrograms on
the Q Series TGA’s when using platinum pans and
20°
C/min heating rate

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TGA: Factors Influencing Baseline
50
•Stability of table
•Hang down wire / beam condition
•Hang down tube condition
•Leveling of TGA
•Cleanliness of the furnace
•Purge gas flow rates

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Effect of Purge Gas Flowrate on Baseline
51
26.87µg
Using Recommended Flowrates
60
70
80
90
Sample
Purge
Flow
(mL/min)
0
10
20
30
40
50
Balance
Purge
Flow
(mL/min)
-20
-10
0
10
20
Weight
(µg)
0 200 400 600 800 1000
Temperature (°C)

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Effect of Purge Gas Flowrate on Baseline
52
71.63µg
Using Other than Recommended Flowrates
10
20
30
40
50
60
Sample
Purge
Flow
(mL/min)
40
50
60
70
Balance
Purge
Flow
(mL/min)
-10
10
30
50
70
Weight
(µg)
0 200 400 600 800 1000
Temperature (°C)

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Balance Sensitivity- 120 µg Calcium Oxalate
53
12.32%
(0.01564mg)
Calcium Oxalate (120µg sample)
Note total weight loss = 15µg !!!
60
70
80
90
100
110
Weight
(%)
50 100 150 200 250 300
Temperature (°
C)

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Sample: 27µg Sodium Tartrate
54
15.56%
(0.004201mg)
Sodium Tartrate water loss
literature value : 15.65%
Note : 4µg weight loss clearly detected !!!!
40
60
80
100
Weight
(%)
60 80 100 120 140 160 180
Temperature (°
C)

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TGA: High Sensitivity Volatiles Analysis
55
0.2162% Volatiles
(0.005198mg)
2.4 mg PET
10C/min
99.7
99.8
99.9
100.0
100.1
Weight
(%)
20 40 60 80 100 120 140 160 180
Temperature (°
C)
2.4 mg PET Bottle
10°C/min

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TGA: Sample Preparation
•Sample mass
10-20mg for most applications
50-100mg for measuring volatiles
•If a TGA has a baseline drift of +/-25µg then this is 0.25% of a
10mg sample
56

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TGA particle size matters, NaCl decrepitation
57
-0.01
0.00
0.01
0.02
0.03
0.04
0.05
0.06
Deriv.
Weight
(%/°
C)
98.0
98.5
99.0
99.5
100.0
Weight
(%)
0 100 200 300 400 500 600
Temperature (°
C)

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TGA: Sample Preparation
58
•Use brass tweezers to eliminate static effects
•Tare a clean sample pan before every run
•Distribute sample evenly over bottom of pan
•Liquid samples - use hermetic pan with a pin-hole lid

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TGA: Sample Pans - Types/Sizes
Deep-walled pans are good for larger mass and low-density materials
Ceramic (alumina)
Platinum
Aluminum
50 µL
100 µL 100 µL 250 µL
500 µL
80 µL
59

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TGA: Sample Pan Selection
60
•Platinum (useful for most materials)
Easy to Clean
Nonporous
Bu can alloy with most metals
•Alumina (Ceramic)
Corrosives/Inorganics
Large samples
•Aluminum (TGA) (designed for one-time use)
Lower cost, disposable
Lower temperature limit (=600°
C)

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Sealed Aluminum Pans
61

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1. Home Position
3. Punching
2. Pre-Punching
Force
Sensor
Punch
Sealed Aluminum Pans and Punching
62

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TGA: Sample Pan Cleaning
63
•All sample pans are reusable
(except Aluminum)
•Flame remaining residue from pan with torch
(do not flame Aluminum pans)
•Scrape off remaining ash (DSC fiberglass brush)

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TGA: Environment Considerations
64
•Avoid areas near heater or air conditioner ducts
•Avoid tables with drawers or those near a door
•For optimum results, use a marble table

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65
Experimental Methods

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Experiment Setup
•Experiments are created in
the Running Queue or the
Design View.
•They are launched from the
Running Queue!
66

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Experiment Setup
•Sample information is entered here
67

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Experiment Setup
68

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Experiment Setup
69

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Segment Statements
70
•The logic of the instrument control software is based upon
segment statements which the user enters during the
design of the experiment.
•These segments are executed during the experiment.

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Method Segments
71

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Method Design: TGA
Segment List
•The Ramp segment heats or cools the
sample at a fixed rate until it reaches the
specified temperature, producing a linear
plot of temperature versus time
•The Equilibrate segment heats or cools
the furnace to the defined temperature,
stabilizes the furnace at that temperature,
then continues to the next segment.
•The Select Gas segment controls the
switching of gas between Gas 1 and Gas
2 for an instrument with a gas delivery
module. This segment is used to
synchronize gas switching at a specific
time or temperature in an experiment.
72

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Segments and Descriptions
73

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Segments and Description
78

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Typical Methods
•Ramp (heating) experiment:
Ramp 20°
C/min. to 800°
C
•Ramp and switch gas
(carbon black content,
residue)
Ramp 20°
C/min. to 650°
C
Select gas: 2
Ramp 20°
C/min. to
1000°
C
79

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Typical Methods – Ramp and Isothermal Hold
80

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Typical Methods
81
•Ramp and switch gas (carbon black content)
Ramp 20°
C/min. to 650°
C
Select gas: 2
Ramp 20°
C/min. to 1000°
C
•High Resolution Ramp
Ramp 50°
C/min. res 5 to 800°
C
(resolve closely spaced peaks)

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General Considerations
Experimental Effects

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TGA Curves are not ‘Fingerprint’ Curves
83
•Because most events that occur in a TGA are kinetic in
nature (meaning they are dependent on absolute
temperature and time spent at that temperature), any
experimental parameter that can effect the reaction rate
will change the shape / transition temperatures of the
curve.
•These things include:
Sample Mass
Heating Rate
Purge gas
Sample volume/form and morphology

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Larger sample mass increases the observed
decomposition temperature
84
0
20
40
60
80
100
Weight
(%)
0 100 200 300 400 500 600
Temperature (°
C)
Polystyrene 17.6 mg
Polystyrene 10.2 mg
Polystyrene 5.4 mg
Polystyrene 2.7 mg
Universal V4.2D TA Instruments

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Higher heating rates increase the observed
decomposition temperature
85
0
20
40
60
80
100
Weight
(%)
0 100 200 300 400 500 600
Temperature (°C)
Polystyrene 20°
C/min
Polystyrene 10°
C/min
Polystyrene 5°
C/min
Polystyrene 1°
C/min
Universal V4.2D TA Instruments
Sample Mass
10mg ±1mg

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Sample Morphology Effects – PET
86
419.58°C 424.58°C
0
20
40
60
80
100
120
Weight
(%)
0 100 200 300 400 500 600
Temperature (°C)
2.9 mg; amorphous PET
2.8 mg; crystalline PET
Universal V3.8A TA Instrum ents
2.9 mg; amorphous PET
2.8 mg; semi-crystalline PET

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High-Heating Rate TGA Analysis
87
60.09% Polypropylene
(2.736mg)
0
20
40
60
80
100
Weight
(%)
0 200 400 600 800 1000
Temperature (°
C) Universal V3.9A TA Instruments
500 °C/min
40°C/min
40% calcium
carbonate

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High-Heating Rate TGA Analysis
88

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What if I need help?
89
•TA Tech Tips
http://www.youtube.com/tatechtips
•Call the TA Instruments Hotline
302-427-4163 M-F 8-4:30 Eastern Time
thermalsupport@tainstruments.com
•Visit our Website
http://www.tainstruments.com/
On-site training e-Training courses
Practical Series Webinars

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90
Part II - Applications

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Part 2
91
General Applications
Improving Resolution
Kinetics and Activation Energy
Evolve Gas Analysis

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92
Basic Applications

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Thermal Stability of Polymers
1: Gas 1 (N2)
3: Gas 2 (air)
Gas Switch
93

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Block versus Random Copolymers
94

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Effect of Epoxy Cure Temperature
95

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Residue Determination - 0.2% Salt Solution
96
Residue:
0.2212%
(0.2160mg)
Method Log:
1: Ramp 5.00 °
C/min to 90.00 °
C
2: Isothermal for 120.00 min
3: Ramp 5.00 °
C/min to 600.00 °
C
4: End of method
0
20
40
60
80
100
Weight
(%)
0 50 100 150 200 250
Time (min) Universal V3.2A TA Instruments
Sample: NaCl – 0.2% in H2O
Size: 97.6300mg

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TGA of Drug A Monohydrate
97
4.946%
(0.7505mg)
-2
0
2
4
6
Deriv.
Weight
(%/min)
80
85
90
95
100
105
Weight
(%)
0 50 100 150 200 250 300
Temperature (°
C) Universal V3.4C TA Instruments
Sample: Drug A Monohydrate
Size: 15.1740mg
Heating Rate: 10°
C/min
Water weight loss
Decomposition

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EVA Copolymer
98
16.87% Acetic Acid
(3.240mg)
-20
0
20
40
60
80
100
120
Weight
(%)
0 100 200 300 400 500 600 700
Temperature (°
C) Universal V3.3B TA Instruments
% Vinyl Acetate = % Acetic Acid *
Molecular Weight(VA) / Molecular
Weight (AA)
VA% = 16.85(86.1/60.1)
= 24.2%
Sample: EVA (25%)
Size: 19.2030mg
Heating Rate: 10°
C/min

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PET w/Carbon Black Filler
99
78.64%
(11.26mg)
20.64%
(2.957m g)
Carbon Black Filled PET
In N2
20.00 °C/min to 650.00 °C
Switch to Air
Ramp 20.00 °C/min to 1000.00 °C
-0.5
0.0
0.5
1.0
1.5
2.0
Deriv.
Weight
(%/°C)
0
20
40
60
80
100
Weight
(%)
0 200 400 600 800 1000
Temperature (°C)
How much
Carbon Black
was in this
sample?

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PET Without Filler
100
85.65%
(16.01m g)
13.99%
(2.614mg)
In N2
20.00 °C/min to 650.00 °C
Switch to Air
Ramp 20.00 °C/min to 1000.00 °C
PET
-0.5
0.0
0.5
1.0
1.5
2.0
Deriv.
Weight
(%/°
C)
0
20
40
60
80
100
Weight
(%)
0 200 400 600 800 1000
Temperature (°C)

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Comparison of Filled Un-Filled PET
101
85.65%
(16.01m g)
13.99%
(2.614m g)
78.64%
(11.26m g)
20.64%
(2.957m g)
M ethod Log:
1: R am p 20.00 °C /m in to 650.00 °C
2: S elect gas: 2
3: R am p 20.00 °C /m in to 1000.00 °C
6.65% C arbon B lack
0
20
40
60
80
100
Weight
(%)
0 200 400 600 800 1000
Tem perature (°C )
PET
Filled PET

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Composite Analysis
102

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EPDM Rubber Analysis
103

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Filled Polymer Analysis
104
Polymer
Carbon Black
Air
(A)
Polymer
Carbon Black
Air
(B)
Light Oil
Polymer +
Heavy Oil
Carbon Black
Air
(C)
100
0
100
100
0
0
WEIGHT
(%)
TEMPERATURE (°
C)
Inert filler
Inert filler
Inert filler

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Effect of Flame Retardant
105
0 200 400 600 800
60
70
80
90
100
TEMPERATURE (°
C)
WEIGHT
(%)
Without Flame Retardant
With Flame
Retardant
Size: 20 mg
Prog.: 10°
C/min
Atm.: Air

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TGA-MS of Flame Retardant
0 100 200 300 400 500
20
40
60
80
100
Temperature (°
C)
TGA
Weight
(%)
MS
Intensity
PVC
PVC + MoO
3
0 100 200 300 400 500
Temperature (°
C)
Benzene
(78 amu)
Benzene is a component of smoke. Much
reduced in the flame retardant sample.

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Vegetable Oil Oxidative Stability
107
0 10 20 30 40 50 60 70 80 90
25
50
75
100
125
TIME (Min.)
TEMP
(°
C)
137
-
WEIGHT
CHANGE
+
Sample Size: 5.18 mg
Temperature: 137°
C
Atmosphere: 0 2
0 2
0.05
57 MINUTES
FIRST DEVIATION
Similar principle to OIT experiment done by DSC

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108
TGA Resolution

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TGA Resolution
109
Introduction: Methods to change
temperature in a TGA experiment
Improving resolution in Standard
(constant heating rate) TGA experiments
Hi-ResTM TGA
Automated Stepwise isothermal TGA

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Temperature-controlled TGA (standard TGA)
vs sample-controlled TGA
110
Temperature-controlled thermal analysis Sample-controlled thermal analysis
Ref:
O. Toft Sørensen and J. Rouquerol (2003). Sample Controlled Thermal Analysis: Origin, Goals, Multiple Forms, Applications
and Future. Kluwer Academic Publishers, Netherlands

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Standard TGA: advantages
111
• Easy to set up
• When the individual decomposition steps occur at well-separated
temperatures, quantitative information for each step can be obtained

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Standard TGA: limitations
112
•Complex thermal scans with broad weight losses
•Overlapping weight losses
Multiple peaks/shoulders
Ref:
J-F. Masson, S. Bundalo-Perc, Thermochimica Acta, 436 (2005), 35–42
Standard TGA of bitumen
800
0 100 200 300 400 500 600 700
Temperature (°C)
120
-20
0
20
40
60
80
100
Weight
(%)
-0.1
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
d(Weight)
/
d(Temperature)
d(Weight
)
/
d(
)
((%)
/
(°C))

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Improving resolution in Standard TGA
experiments
113
• Means of Enhancing Resolution
Slower heating rate
Reduced sample size
Pin-hole hermetic pans (self-generating atmosphere)

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Impact of heating rate on resolution: 20°C/min
100
Temperature (°
C)
150 200 250 300
110
100
90
80
70
60
0 50
WATER
10
8
6
4
2
0
-2
13 minutes
20°
C/min
Weight
(%)
(
)
Deriv.
Weight
(%/min)
114

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Impact of heating rate on resolution: 1°C/min
0 50 100 150 200 250 300
60
70
80
90
100
-0.2
0.0
0.2
0.4
0.6
0.8
1.0
Temperature (°
C)
170 MINUTES
1°
C/min
(
)
Deriv.
Weight
(%/min)
Weight
(%)
115

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Effect of sample mass on resolution: bitumen
116
Ref:

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Resolution enhancement using a pinhole
hermetic DSC pans
117
Pt TGA pan
Tzero Hermetic Pinhole Lid
(75 µ
µ
µ
µm laser drilled pinhole)
Tzero pan

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Resolution enhancement using a pinhole
hermetic DSC pans: gypsum
•The partially dehydrated mineral is called calcium sulfate hemihydrate
or calcined gypsum (CaSO4·½H2O).
• As heating continues, the anhydrite, CaSO4, is then formed.
CaSO4·½H2O + heat → CaSO4+ ½H2O
CaSO4·2H2O + heat → CaSO4·½H2O + 1½H2O (steam)
• Heating gypsum between 100°
C and 150°
C (302°
F) partially
dehydrates the mineral by driving off exactly one and a half moles of
the water contained in its chemical structure.
118

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Theoretical Mass Losses of Gypsum
• CaSO4·2H2O + heat → CaSO4·½H2O + 1½H2O
A loss of 1½H2O = 100*(MW. 1½H2O/ MW. CaSO4·2H2O)
= 15.69%
• CaSO4·½H2O + heat → CaSO4+ ½H2O
A loss of ½H2O = 100*(MW. ½H2O/ MW. CaSO4·2H2O)
= 5.23%
• Total weight loss = 15.69% + 5.23% = 20.92% (2 mols
H2O)
119

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Effect of DSC Pinhole pans on TGA resolution
120
14.90%
(1.050mg)
4.830%
(0.3405mg)
Standard
TGA Pan
Pin Hole
DSC Pan
0
1
2
[
–
–
–
–
]
Deriv.
Weight
(%/°
C)
55
65
75
85
95
105
Weight
(%)
0 50 100 150 200 250
Temperature (°
C)
Gypsum
Theoretical: 15.69%
Theoretical: 5.23%

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Sample-controlled TGA to improve TGA
resolution
121

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Hi-ResTM TGA
• Faster heating rates during
periods of no weight loss, and
slowing down the heating rate
during a weight loss – therefore
not sacrificing as much time
• Hi-ResTM TGA can give better
resolution or faster run times,
and sometimes both
122
• In a Hi-ResTM TGA experiment the heating rate is controlled by the rate of
decomposition.

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Hi-ResTM TGA of Calcium oxalate
123
1000
0 100 200 300 400 500 600 700 800 900
Temperature (°C)
110
30
40
50
60
70
80
90
100
-0.25
1.75
1.50
1.25
1.00
0.75
0.50
0.25
0.00
100
-100
-50
0
50
calcium oxalate - Hi-ResTM TGA
50°
C/min, resolution 5, sensitivity 1

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Std TGA 20°C/min
Time = 38.64 min
Std TGA 1°C/min
Time = 771.46 min
Hi-Res TGA 50°C/min; Res 5
Time = 125.29 min
0
20
40
60
80
100
Weight
(%)
0 200 400 600 800
Temperature (°C) Universal V2.5D TA Instruments
Hi-ResTM TGA vs. Std TGA of Nylon/PE Blend
124

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1. Sensitivity 1.0
2. Ramp 50°
C/min, Res. 4.0 to 1000°
C
Sensitivity: typically varies from 0 to 8.0
Controls the response of the Hi-Res system to
changes in decomposition rates (∆ wt%/min)
Determines the increase in decomposition rate
that warrants a reduction in the heating rate (or
vice-versa)
Higher sensitivity values make the Hi-Res
system more responsive to small changes in the
rate of reaction
Programming a Hi-ResTM TGA experiment –
sensitivity number
125

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1. Sensitivity 1.0
2. Ramp 50°
C/min, Res. 4.0 to 1000°
C
Resolution : typically varies from -8.0 to 8.0
Adjusts the heating rate based on the
sample decomposition rate (wt%/min)
As the decomposition rate increases, the
heating rate is further decreased (and vice-
versa).
Higher resolution number (absolute value)
results in a greater reduction in heating rate
at smaller values of wt%/min
Programming a Hi-ResTM TGA experiment –
resolution number
126

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Effect of sensitivity settings on TGA data
Res = 5 for all Hi-Res experiments
1 C/min std TGA
Sensitivity setting 1
127

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Resolution = 1
Sensitivity = 1
Resolution = 8
Sensitivity = 1
Note that increasing resolution setting increases the resolution of each transition and
simultaneously reduces the transition temperature.
Resolution: 1
Resolution: 8
Sensitivity = 1 for all curves
Effect of resolution settings on TGA data
Hi-Res TGA on ethylene-vinyl acetate copolymer
128

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Optimizing the Hi-ResTM TGA settings
129
• Sensitivity of 1 and resolution of 4 are good starting
points. Higher resolution number means slower heating
rate.
• Increasing the resolution number if you need further
separation of derivative peaks

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Two modes of Hi-ResTM TGA
130
Hi-ResTM TGA
Dynamic mode
(wt%/min is
variable)
Constant
reaction mode
(wt%/min is
constant)

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Compare Hi-ResTM TGA vs. standard TGA at
10°C/min – Ethylene Vinyl Acetate copolymer
131

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Use of Hi-ResTM TGA for determination of free
and bound water in pharmaceuticals
Standard TGA Hi-ResTM TGA
132
Ref:
TA Instruments application note TS17
Note the use of 10 C/min heating rate in the Hi-ResTM TGA as the sample loses mass
rapidly

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800
0 100 200 300 400 500 600 700
Temperature (°C)
120
-20
0
20
40
60
80
100
Weight
(%)
-0.1
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
d(Weight)
/
d(Temperature)
d(Weight
)
/
d(
)
((%)
/
(°C))
Standard TGA 10°C/min of bitumen sample
Lower
Temp
Region
Middle
Temp
Region
Higher
Temp
Region
air purge
Ref:
133

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600
0 100 200 300 400 500
Temperature (°C)
-1.00
1.25
1.00
0.75
0.50
0.25
0.00
-0.25
-0.50
-0.75
standard TGA
Hi-res TGA - dynamic mode
Standard TGA vs Hi-Res TGA (dynamic mode)
of bitumen sample
134
Ref:
Heating rate: 50 C/min
Res: 3
Sen: 5

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350
150 200 250 300
Temperature (°C)
0.0
1.0
0.5
Hi-res TGA - constant reaction rate
standard TGA
Constant Reaction Rate TGA of bitumen sample
dm/dt = 0.316%/min
resolution: -4,
sensitivity: 1
Ref:
135

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Hi-ResTM TGA- Advantages
136
•Relatively simple to develop method
•Rapid survey over wide temperature range with excellent
resolution
•High resolution with equal/better productivity, even on
unknowns

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Automated Stepwise Isothermal TGA (SWI)
137
•Heating stops (goes isothermal) when a certain rate of
weight loss is reached, then resumes after this rate falls
below a second defined value
•Operator defines the values for the rate of weight loss
•Incorrect values can cause artifacts that appear as
‘additional’ mass losses
•Correctly set up, can give excellent resolution, but takes
quite a bit longer

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Automated Stepwise Isothermal TGA (SWI)
138
•Advantages
Sample held isothermal until transition completed - thus
excellent resolution of overlapping transitions
Permits careful control of reaction environment
Programmable on any TGA
•Disadvantages
Requires method development. May require several scans
to optimize run conditions
Inappropriate parameter choices may produce artifacts
Long run times

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Standard TGA of Polyvinyl Acetate
139
Basis for Entrance
Threshold
Ref:
Thermal Applications Note TN40 – Optimizing Stepwise Isothermal Experiments in
Hi Res TGA

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Typical SWI Thermal Method
140
1. Abort next segment if %/min 4
2. Ramp 10°
C/min to 1000°
C
3. Abort next segment if %/min 0.4
4. Isothermal 1000 min
5. Repeat 1 until 1000°
C

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SWI of Polyvinyl Acetate
141
Ref:
Thermal Applications Note TN40 – Optimizing Stepwise Isothermal Experiments in
Hi Res TGA

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Hi-ResTM TGA of lubricating oil (Res. 4)
254.73°
C
359.23°
C
24.72% First Weight Loss Event
(2.959mg)
39.05% Second Weight Loss Event
(4.674mg)
-0.5
0.0
0.5
1.0
1.5
2.0
Deriv.
Weight
(%/°
C)
20
40
60
80
100
120
Weight
(%)
0 200 400 600 800 1000
Temperature (°
C)
0 10 20 30 40 60 70 80 85
Time (min)
142

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Hi-ResTM TGA of lubricating oil (Res. 6)
205.52°
C
325.71°
C
412.42°
C
(2.854mg)
(5.012mg)
4.357% Third Weight Loss Event
(0.5488mg)
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
Deriv.
Weight
(%/°C)
20
40
60
80
100
120
Weight
(%)
0 100 200 300 400 500 600
Temperature (°
C)
0 25 100 150 250 300 325 343
Time (min)
143

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Stepwise Isothermal TGA of lubricating oil
(2.623mg)
(4.231mg)
5.655% Third Weight Loss Event
(0.6660mg)
20
40
60
80
100
120
Weight
(%)
0 100 200 300 400 500 600
Temperature (°
C)
0 25 75 250 255
Time (min)
144

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145
TGA
Decomposition Kinetics

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Decomposition Activation Energy by MTGATM
146
How is decomposition
kinetics measured by TGA?
Conventional method for
Activation Energy
A guide to Modulated TGA
Applications of MTGA for

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Kinetic Analysis
•The rate at which a kinetic process proceeds depends not
only on the temperature the specimen is at, but also the
time it has spent at that temperature.
•Typically kinetic analysis is concerned with obtaining
parameters such as
activation energy (Ea),
reaction order (n), and
generating predictive curves for conversion ().
147

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Kinetics by TGA
: =
−
−
148
0
T
Conversion,
%
Initial weight:
win
100
Weight at T:
wT
Final weight:
wf
Weight,
%
α

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Kinetic Analysis
Activation energy (Ea) can be defined as the minimum amount of energy
needed to initiate a chemical process.
State 1
State 2
Ea
149

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Introduction: Decomposition Kinetics
Thermal decomposition kinetics can be represented by the
following generic kinetic equation:
%
%'
= ( )(+), where:
α - conversion fraction (normalized weight on a TGA curve)
%
%'
- rate of conversion (rate of weight loss on a TGA curve)
f(α) - rate function dependant upon conversion fraction
k(T) - rate function dependant upon temperature
150

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Almost without exception this is taken to be the
Arrhenius equation, so:
-
-.
= ( / 012 3
⁄
α - conversion fraction (normalized weight on a TGA curve)
%
%'
- rate of conversion (rate of weight loss on a TGA curve)
f(α) - rate function dependant upon conversion fraction
/ - pre-exponent factor
Ea - activation energy
R - gas constant
151

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Decomposition Kinetics by TGA
•Traditional methods include isothermal and constant
heating rate techniques.
•ASTM E1641
Based on method of Flynn and Wall – Polymer Letters, 19,
323 (1966). Requires collection of multiple curves at
multiple heating rates.
152
Weight
(%)
Increasing
Heating Rate
Increasing
Heating Rate

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Heating rate:
6 =
-+
-.
Thus
-
-+
=
/
6
012 3
⁄
(
For a single heating rate:
7
-
-+
6
(
= 7 / −89 :+
⁄
At a select α conversion
- 7 - -.
⁄
-+0;

= −89 :
⁄
153

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Recipe for Activation Energy by ASTM E1641.
Polymer Decomposition
• Run TGA experiment on polymer at 4-6 different heating rates
• Obtain a temperature at an isoconversional point – for
example 10% weight loss for each heating rate
• Plot the ln of the heating rate (β
β
β
β) versus 1/T (temperature
units must be in Kelvin)
• Slope of the line is (-E
E
E
Ea
a
a
a/R). Multiply the slope of the line by –
(8.314 x 10-3) to obtain the activation energy in kJ/mol.
154
TA Instruments Application Note TA251
Blaine, R. L. and Hahn, B. K., “Obtaining Kinetic Parameters by Modulated Thermogravimetry,” J.
Therm. Anal., Vol. 54, 1998, p. 694.

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PTFE Decomposition by ASTM E1641
155
10 % Conversion

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Heating Rate (β
β
β
β) °
C / min ln (β)
Temperature at
10 % Weight
Loss (°
C) 1/T (K)
10 2.303 532.98 0.001240
8 2.079 529.54 0.001246
6 1.792 525.53 0.001252
4 1.386 519.36 0.001262
2 0.693 509.48 0.001278
1 0.000 499.30 0.001295
Intercept of ln(β
β
β
β) vs 1/T 55.25
Slope of ln(β
β
β
β) vs 1/T -42685
Activation Energy Ea
(kJ/mol)
354.9
156

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157

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*J.H. Flynn, Thermal Analysis, R.F. Schwenker and P.D. Garn, Eds., Academic Press, Budapest, 2, 1969, 1111-1123
158
Temperature is alternated between 245 and 247°
C.
Tem
perature
(°C)
T2
Conversion values ~ constant.
Temperature is altered between
245 and 247 ºC
T1
Valleys
Peaks

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From the general rate equation at each temperature T1 and T2 :
- -.
⁄ ?
= ( / 012 3?
⁄
and - -.
⁄ @
= ( / 012 3@
⁄
Assuming f(α) is the same (constant conversion values), take the ratio
and solve for Ea:
-; -A
⁄ = 012 3 ; ?
⁄ 0; @
⁄
⁄
89 =
: 7 -; -A
⁄
1 +A
⁄ − 1 +;
⁄
This method is called the Factor Jump Method.
Solution for Ea Assuming Constant Conversion
159

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PS: Temperature Step Change Experiment
0.32%/min
0.40%/min
89.55%
90.03%
Temperature Isotherms between 300 and 305°
C.
Ea = [8.314ln(.0032/.004)]/(1/578-1/573)
Ea = 122.9 kJ/mole at 10% conversion
Ea = [8.314ln(.0032/.004)]/(1/578-1/573)
Ea = 122.9 kJ/mole at 10% conversion
160
Temperature isotherms
between 300 and 305 ºC
90.03%
89.55%
0.32 %/min
0.40 %/min

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For sinusoidal temperature:
T = Ti + Ta sin(ωt)
Ti - isothermal temperature
Ta - modulation amplitude
For peak and valley temperatures:
TP = Ti + Ta TV = Ti - Ta
After substitution and rearrangement
89 = : 7 -; -A
⁄
+
A
− +9
A
2+9
Proceed from Step Change to Sinusoidal
Change in Temperature
161

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PS: Quasi-Isothermal Experiment @ 290°C
90.00%
112.4kJ/mol
162
90.0 %
112.4 kJ/mol

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Extension to Modulated Temperature Ramping
163

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Advantages of MTGATM
•One run needed to obtain activation energy.
•Activation energy is a signal in the data file.
•Comparable with Flynn-Wall method for calculated Ea with the benefit
of the reduced time.
•Method works under quasi-isothermal or ramping conditions.
•Activation energy is obtained as a continuous curve and so can be
manipulated numerous ways. For example, it can be plotted as a
function of conversion.
•Can be combined with Hi-Res™ to speed up experiments and more
accurately handle multiple weight loss events.
164

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Setting Up MTGATM Experiment
• Three parameters must be defined:
• heating rate
• modulation period
• modulation amplitude
• What is the effect of these parameters on the data? What are the optimum
values?
165

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General Guidelines
•Higher amplitudes improve signal/noise and increase
precision, but require longer periods to make sure the
sample is remaining in equilibrium.
•Longer periods ensure equilibrium, but require slower ramp
rates so the minimum 5 cycles per transition can be
obtained.
•A scouting run at 10 °
C/min is useful to determine width of
transitions.
•Range of consistent results:
Period = 200-300 s (practical range: 100 – 500s)
Amplitude = 3-5 °
C (practical range: 1 – 10 °
C)
Ramp Rate = 1 °
C/min (practical range: 0.5 – 2 °
C/min)
166

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MTGATM – Typical Values
•Modulation period – 200 seconds.
•Amplitude – 4-5°C.
•Heating rate – 1 to 2 °C/min.
•Plot derivative of weight loss and calculate the width at
half height of the derivative weight loss peak.
Need at least 5 modulation cycles across this region.
167
Weight
(%)

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PTFE: Modulated Ramping Experiment
168
Polytetrafluoroethylene
Negligible
weight change
Negligible
weight
change

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MTGA Precision: PTFE
Repeatability = 2.8X Standard Deviation
Conversion
(%) #1 #2 #3 #4 #5
Average
(kJ/mol)
Standard
Deviation
(kJ/mol)
Relative
Stnd Dev
(%)
1 333.0 342.4 335.8 345.9 340 339.42 5.14 1.51
2 334.9 329.3 330.8 330.8 327.7 330.70 2.67 0.81
5 319.3 322.6 323.7 319.7 323.1 321.68 2.03 0.63
10 313.1 314 311.9 316.2 318.6 314.76 2.66 0.85
169
C.G. Slough The Accuracy, Repeatability, and Reproducibility of Activation Energy Values Measured by
Modulated Thermogravimetry. J of Testing and Evaluation V. 42, N. 6 (2014)

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Decomposition of PP by Flynn-Wall Method
0.0 0.2 0.4 0.6 0.8 1.0
150
180
210
240
270
Eα
α
α
α
/
kJ
mol
-1
α
Atmosphere Ea* / kJ mol-1
N2 244
N2 216
N2 214
N2 160
N2 115 – 200
N2 130 – 200
N2 230
Vacuum 257
Ar 98, 328
Thermal Analysis of Polymers: Fundamentals and Applications. Chapter 3. Edited by by J. Menczel and R. B.
Prime (2009)
170
* Data obtained from multiple publications

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PP: Modulated Ramping Experiment
Literature: Ea = 232 ± 27 kJ/mol (12 % standard deviation)
This study: Ea = 200 ± 19 kJ/mol (standard deviation 9.5 %)
171

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PP: Modulated Ramping Experiment
172

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TGA Kinetics - Estimated Lifetime
TEMPERATURE (°
C)
1.5
1.6
1.7
1.8
1.9
10
100
1000
10000
100000
1000000
1000/T (K)
ESTIMATED
LIFE
(hr.)
260 280 300 320 340 360
1 century
1 decade
1 yr.
1 mo.
1 week
1 day
ESTIMATED
LIFE
TA Instruments Application Note TA125
Estimation of Polymer Lifetime by TGA Decomposition Kinetics
173

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TGA Kinetics
• ASTM committee E37 on Thermal Methods is currently
developing a standard for kinetics by either the Factor
Jump method or MTGA
• Modulated TGA is a comprehensive method to obtain an
activation energy of decomposition in a single run
• Data by MTGA is comparable to that of the Flynn-Wall
method
• It can be a powerful tool to compare energetics of similar
systems (for example, composites of close compositions,
polymers with additives)
174

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Thank You
The World Leader in Thermal Analysis,
Rheology, and Microcalorimetry
201

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202
Appendix A
Calibration Steps

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TGA: Certified Calibration Kit
203
•Certified Temperature Calibration Kit
(P/N 952384.901)
•Secondary Temperature Calibration Materials
(Nickel, Alumel)
•Curie Temperatures traceable to National
Reference Laboratories (NIST, LGC)
•Universal Magnet
•ASTM E1582 test method
•Detailed ISO style calibration instructions

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Calibration
204
•Weight Calibration
Manual – done with pan and known calibration weight
Accessed through TRIOS software CalibrateWeight
Automatic – done with differential weights from accessory
kit.
Also accessed with CalibrateWeight
Platinum reference pan has to be on the counter balance.

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Calibration - Weight
205
Choose Weight
Calibration

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Calibration – Weight (Auto)
206

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207

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208
After Calibration is Completed

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209
Enter the mass of the calibration
weight

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210

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211
Simply reload the mass to verify – mass
difference of ~ 0.005%

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Calibration - Temperature
212
•Temperature – Curie Point
•Up to 5 standards may be used
•Experiment will be set up automatically
•Multiple calibrants must be analyzed at once
•Well documented in the help menu

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Calibration – Choose Calibrant, Method is
Automatically Generated
213

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Calibration – Temperature
214
Choose ‘New’

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•Choose the appropriate
standard – instrument will
automatically choose the
parameters.
•Be sure to choose the
correct pan number and
type. You can vary the
heating rate, but the
lower and upper
temperature boundaries
are fixed.
•If you choose to send the
run to the ‘Queue’, you
can simply add another
Curie standard as the
next run.
215

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216
From the ‘Results’
Pane, Choose both
the Alumel and
Nickel Runs

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217
Electromagnet
Switched ON –
Apparent Weight Gain
Curie Point

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218
Choose ‘Calibrations’
and ‘TGA Temperature’

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219
Dialogue Box
Shows Summary
of Calibration –
Choose ‘Save
and Apply’ if Data
is OK

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Calibration – Temperature – Completed!
220

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Calibration – Temperature – Verification
221
•Run Curie samples in the ‘Standard’ mode – not
‘Calibration’
•Analyze Curie Point
•Both standards can be run simultaneously

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Calibration – Temperature: Verification
222
Alumel
Nickel

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Calibration – Temperature – Verification
223

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224
•Protocol is determined by your lab and needs, but there is
no substitute for sound analytical chemistry!
•You simply have to be confident that the data you provide
is correct.
•TA recommends verification on a regular basis.
•Verification is simply running a known standard in the
standard mode and determining the Curie Point for
temperature and …
•Simply placing a known weight on a tared pan and
checking the mass measured by the balance.
•Control charts allow for statistical monitoring of instrument
performance.
•Refer to any analytical chemistry text

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How Often Do I Calibrate? – The Case for
Control Charting
225
•Example:
Laboratory A has TA Instruments come in for a preventive maintenance
visit every January. This visit includes calibration of the temperature and
mass.
No further calibration or verification is performed until September of the
same year when an internal customer questions her data.
A check of the calibrations shows that the instrument is reading 20 °
C too
high and the mass 20 mg too low.
When did the calibration change?
With no verification protocol in place, all of the data for the previous 9
months is considered un-reliable. Some protocols require that each client
be notified about the potential discrepancies in their data.
A weekly verification protocol and control chart maintenance would
minimize the amount of suspect data.
Verification of an alumel / nickel calibration takes about 20 minutes.
Verification of the mass calibration using the supplied differential masses
takes less than 10 minutes

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226
•Standard Reference Materials come with a certificate of
measurement that identify:
The best estimate of the known true value of the reference
material.
The uncertainty of the best estimate value. This value
typically represents the 95% confidence limits, (twice the
standard deviation or 2σ), but you must read the certificate
carefully to be sure.

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• Standard deviation
and confidence limits
Miller and Miller; Statistics for Analytical
Chemistry, 2nd Edition; Ellis Horwood
Limited
227

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Calibration - Traceable Standards
228
•Certified – material has been tested using a formal testing
procedure and the signature attests to the validity of the
results
•Traceable – certifies that a documented chain of
comparisons exists connecting the standard to a reference
material maintained by a national metrology laboratory
such as NIST or LGC.

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229

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230

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231

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232
•Should I expect to obtain the same uncertainty values
observed by the certifying agency?
•Not necessarily!
•What should my uncertainty value be? Where do I start?
•A good place is the precision and bias section associated
with the ASTM method for the analysis – in this case
ASTM E1582.
•ASTM Statement:

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233
•How do I determine if my instrument needs calibration?
•One suggestion– maintain control chart of verification
runs. Verification runs are made in the standard mode.
•Accumulate a statistically significant number of runs.
•Decide on appropriate boundaries for the uncertainty
interval.

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234
•What is a statistically significant number of observations?
•The Standard Error of the Mean (SEM) is given by the
function:
ns
observatio
of
number
deviation
standard
=
=
=
n
where
n
SEM
σ
σ

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235
1 10 100
Log n (Number of Measurements)
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
1
/
(n)^(1/2)
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
1
/
(n)^(1/2)
N=10 N=30

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