Thermogravimetric analysis (TGA) measures the change in mass of a sample as it is heated or cooled over time. It works by precisely measuring and recording the weight of a sample as the temperature changes. TGA is useful for determining a material's thermal stability and its compositional components, as well as investigating decomposition reactions and absorbed moisture content. A TGA instrument consists of a microbalance, furnace, temperature controller, and recorder to plot weight changes against temperature or time. Heating rates, atmosphere, and sample characteristics can impact the resulting TGA curve. Common applications include measuring purity, stability, and phase changes.

1. THERMOGRAVIMETRIC ANALYSIS (TGA)
Yudhishthir singh baghel
(Pharmaceutics)
ysb096@gmail.com
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2. THERMAL ANALYSIS
• Thermal analysis is a branch of materials science & a group of
analysis which study the property of material when the change
with temperature .
• In this technique mass of the substance is measure as the form of
temperature while it a subjected to control temperature.
Types of thermal analysis
 Thermogravimetric Analysis (TGA or TG)
 Differential Scanning Calorimetry (DSC)
 Derivative Thermogravimetry(DTG)
 Differential thermal analysis (DTA)
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3. INTRODUCTION (TGA)
 Thermogravimetry(TG) is the branch of thermal analysis which
examines the mass change of a sample as a function of temperature
(in the scanning mode) or as a function of time (in the isothermal
mode).
 Thermogravimetric analysis is a method of thermal analysis in which
changes in physical and chemical properties of materials are
measured as a function of increasing temperature rate or as a
function of time.
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4. Types of Thermogravimetry
There are three types of Thermogravimetry :
1. Isothermal /static Thermogravimetry
2. Quasistatic Thermogravimetry
3. Dynamic Thermogravimetry
1.Isothermal /static Thermogravimetry: in this technique the sample
weight is recorded as a function of time at constsnt temperature.
2. Quasistatic Thermogravimetry: in this technique the sample is
heated to constant weight at each of the series of increasing
temperature.
3. Dynamic Thermogravimetry: in this technique a sample is heated in
an environment whose temperature is changing in temperature
manner generally at linear rate .
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5. Thermo gravimetric analysis(TGA)
Principle:
 In Thermogravimetric analysis, mass of the substance is
measure as the function of temperature while it is subjected to
control temperature program the resulted is TG curve or
Thermogravimetric curve time or temperature is plotted on x-
axis or mass is plotted on y-axis.
 Temperature - 0°c -2000°c
 Change in mass of our analyte is studied because of different
physical or chemical transition.
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6. Cont…
 It is used in analysis of volatile products, gaseous products
lost during the reaction in Thermoplastics, Thermosets,
elastomers, films, fibers, paints etc.
 The change in the weight of the substance is recorded as a
function of temperature or time. The temperature is increased
at a constant rate for a known initial weight of the substance
and the changes in weights are recorded as a function of
temperature at different time interval.
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7. Types of transition
Two types of transition occurs
1. Physical transition
2. chemical transition
1.Physical transition
• Adsorption
• Desorption
• Sublimation
• Evaporation
• Vaporization
2.Chemical transitation
• Oxidation
• Reduction
• Chemosorption
• Loss on drying
• degradation 7

8. Types of Graph
1.Disorption
2. Adsorption
3. Polymer analyte
4. Loss on drying
5. Oxidation followed by decomposition
Instrumentation
Components of instrumentation:
A. Recording balance
B. Sample holder
C. Furnace
D. Furnace temperature programmer/ controller
E. Recorder 8

9. Block diagram of a Thermobalance
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10. • TG curves are recorded using a Thermobalance. It consists of
an electronic microbalance, a furnace
• It consists of-
1) Microbalance
2) Recorder balance
3) Sample holder
4) Furnace
5) Recorder
6) Data recording unit
7) Heating rate
8) Time measurement
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11. 1.Microbalance
• It is the most important component of thermobalance. It is used
to record a change in mass of sample or substance.
• An ideal microbalance must possess following features:
a) It should provide electronic signals to record the change in mass
b) It should have the capacity of auto weight
c) It operating should be user friendly
d) Modern microbalances have the ability to be not affected by
vibrations
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12. 2. Recorder balance
Types of recorder balance
1. Deflection balances
2. Null point balances
1. Deflection balances: They are of following types:
a) Beam Type
b) Helical Type
c) Cantilevered Beam
d) Torsion Wire
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13. (a) Deflection balances
Deflection balances are 4 types :-
• In these balance,the conversion of deflected beam take place into
weight change
• In these balance, elongation or contraction of spring occurs with
change in weight which is recorded by help of transducer.
• In this the beam is attached to hard torsion wire which act as
fulcrum
• In this balance, one end of beam is fixed and on the other end
sample is placed.
• (b) Null point balancesIt consist of sensor which detects the
deviation from the null point and restores the balance to its null
point by means of restoring force.
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14. 3. Sample holder
• The sample to be studied is placed in sample holder or crucible. It
is attached to the weighing arm of microbalance.
• There are different types of crucibles used such as
a) Shallow pans
b) Deep crucibles
c) Loosely covered crucibles
d) Retort cups
They are made from platinum,aluminium,quartz or alumina and
some other materials like graphite, stainless steel, glass etc.
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15. 4. Furnace
• The furnace should be designed in such a way that it produce a
linear heating range.
• It should have a hot zone which can hold sample and crucible and
its temperature corresponds to the temperature of furnace.
• The temperature ranges can affect the internal atmosphere of
furnace chamber therefore, it is necessary to choose specific type
of furnace according to the temperature ranges.
• Coils used are made of different materials :-
a) Nicrome wire or ribbon
b) Platinum
c) platinum 10% rhodium Alloy
The size of furnace is important .
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16. 5.Recorder
• The output from the microbalance and furnace are recorded using
either chart recorder.
• The recording systems are mainly of 2 types:-
1. Time- base potentiometric strip chart recorder
2. X-Y recorder
• in the X-Y recorder, we get curves having plot of weights directly
against temperatures.
• However, the percentage mass change against temperature or
time would be more useful.
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17. 6.Heating rate
• It is the rate of temperature increases, which is customarily
quated in degrees per minute. The heating or cooling rate is used
to be constant when the temperature/time curve is linear.
7.Time measurement
• It is done by thermocouple. Different materials are used for
measuring different ranges of temperatures i.e. chromal or
alumel thermocouple are used for T=1100°c
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18. Factors affecting the TG curve
The factors which may affect the TG curves are classified into two main groups-
(1) Instrumental factors
(a) Furnace heating rate
(b) Furnace atmosphere
(c) Sample holder
(2) Sample characteristics includes
(a) Weight of the sample
(b) Sample particle size
(c) Heat of reaction
(d)Compctness of the sample
(e)Previous history of the sample
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19. 1.Instrumental factors
• Furnace Heating rate:
The temperature at which the compound (or sample) decompose
depends upon the heating rate is high, the decomposition
temperature is also high. A heating rate of 3.5°c per minute is
usually recommended for reliable and reproducible TGA.
• Furnace atmosphere:
The atmosphere inside the furnace surrounding the sample has a
profound effect on the decomposition temperature of the sample.
A pure nitrogen gas from a cylinder passed through the furnace
which provides an inert atmosphere.
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20. 2.Sample characteristics
a)Weight of sample: A small weight of sample is recommended using
a small weight eliminates the existence of temperature gradient
throughout the sample
b)Particle size of sample: The particle size of sample should be small
and uniform. The use of large particle may result in apparent very
rapid weight loss.
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21. Applications
1. Physical transition
2. Chemical transition
3. Loss of drying
4. Purity of analyte
5. Stability of analyte
6. Determination of bound and unbound water begins at room
temperature due to dry gas flowing over sample
7. TGA, we can determine the purity and thermal stability of
both primary and secondary standard.
8. corrosion studies
9. Automatic Thermogravimetric analysis
10. Evaluation of suitable standards
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22. References:-
 Skoog, Douglas A, F James Holler and Timothy Nieman, Principles of
Instrumental Analysis,5th edition 2001.
 Gurdeep R. Chatwal, Sham k. Anand, instrumental Method of chemical
analysis,5th edition, Himalayan publishing house,page no-2.701
H.H.Willard, L.L Merrit Jr.J.A Dean,F.A Settle Jr.instrumental Method of
Analysis.Wadsworth Publishing Company,USA 1986
Sharma B.K. Goel publishing House “Instrumental Methods of Analysis” pg.234-
237.
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