Thermal analysis Thermogravimetric analysis

1. DEPARTMENT OF PHARMACEUTICAL SCIENCES
RASHTRASANT TUKADOJI MAHARAJ NAGPUR
UNIVERSITY, NAGPUR - 440033
THERMOGRAVIMETRIC ANALYSIS
PRESENTED BY
TAHMINA KHAN
M. PHARM. FRIST YEAR
PHARMACEUTICAL CHEMISTRY

2. CONTENT
• INTRODUCTION
• TYPES OF THERMOGRAVIMETRY
• INSTRUMENTATION
• THERMAL CURVE
• FACTORS AFFECTING THE TGA
• APPLICATIONS OF TGA
• REFERENCE

3. INTRODUCTION
• The thermogravimetric analysis or thermal gravimetric analysis
(TGA) is method of thermal analysis in which the mass of the
sample is measured over time as the temperature change.

4. PRINCIPLE
• The basic principle of TGA is that as a sample is heated, its mass
change. This change can be used to determine the composition of a
material or its thermal stability up to 1000˚C
• Usually, a sample losses weight as it is heated up due to
decomposition, reduction or evaporation oxidation or absorption.

5. TYPES OF THERMOGRAVIMETRY
Types of
Thermogravimetry
Isothermal
Thermogravimetry
Quasistatic
Thermogravimetry
Dynamic
Thermogravimetry

6. • Isothermal or static Thermogravimetry :
In the technique the sample weight in recorded as function of time at
constant temperature.
• Quasistance Thermogravimetry :
In this technique the sample is heated to constant weight at each of series of
increases temperature.
• Dynamic Thermogravimetry :
In this technique the sample is heated in an environment whose temperature
is changing in predetermined manner generally linear rate , this type is
generally used.

7. INSTRUMENTATION
• Thermogravimetric analysis is conducted on an instrument referred
to as a thermogravimetric analyzer.
• Thermogravimetric analyzer continuously measures mass while the
temperature of a sample is changed over time.
• Mass, temperature and time considered as base measurement in
thermogravimetric analyzer.

8. • A typical thermogravimetric
analyzer consist of ;
1. A furnace controlled
thermobalance
2. A furnace which can be heated so
that, the temperature with time
3. Recorder

9. • The apparatus required for TGA analyzer are:
1. Balance
2. Sample holder
3. Furnace
4. Furnace Temperature Programmer (Thermocouple)
5. Data Recorder

10. BALANCE
• There are two types of balance used in TGA-
Null point type –
This uses appropriate sensing element (sensor) which detects any slightly
deviation of the balance.
Deflection type –
Based on either conventional analytical balance
consisting of -
Helical Beam
Torsion Cantilever

11. SAMPLE HOLDER
• This is most important in accurate thermogravimetric analysis.
• Depending upon the nature of sample, its weight and quantity to be
handled, different size and shape of sample holders known as crucibles are
employed.
• These are constructed from various materials like glass, quartz, aluminum,
stainless steel, platinum etc.
• These generally are of two types:
1. Shallow pan for holding samples which eliminates gas, vapors or
volatile matter by diffusion during heating or.
2. Deep crucible for general purpose.

12. FURNACE
• Must be designed in such a fashion so as to incorporate an appropriate
smooth input thereby maintaining either a fixed temp. or predetermined
linear heating program. (e.g.- 6 c/min)
• Temperature control is achieved via a thermocouple mounted very close
to the furnace-winding.
• Maximum operational temp. may be obtained using different
thermocouple
• as indicated below:
SR NO. SPECIFICATION MAX. TEP.
1 Nickel-chrome (nichrome) 1100
2 Platinum-rhodium 1450
3 Graphite-tube furnace >1500

13. FURNACE TEMPERATURE PROGRAMMER
• These are the controller which can provide gradual rise of
temperature at a fixed rate.
• This device has a coarse and fine control knobs through which
desired temperature with respect to ratel time can be obtained.
• This controlling is done by increasing voltage through the heated
element by motor driven variable transformer or by different
thermocouples.

14. THERMAL CURVE (THERMOGRAM)
(X- Axis) can be displayed as temperature and
(Y- Axis) can be displayed as weight (%).

15. FACTORS AFFECTING THE TGA
(1) Instrumental factors
(a) Furnace heating rate
(b) Furnace atmosphere
(2) Sample characteristics
(a) Weight of the sample
(b) Sample particle size

16. APPLICATIONS OF TGA
• TGA is used as a technique to characterize materials used in various
environmental, food, pharmaceutical, and petrochemical applications.
• TGA can be used to evaluate the thermal stability of a material In a desired
temperature range.
• Can determine the purity of a mineral, inorganic compound, or organic
material.
• TGA is used to study the kinetics of the reaction rate constant.

17. Thermogravimetric analysis(TGA) is a powerful technique for the
characterization of the decomposition or weight loss properties of
materials. The technique provides the following useful information:
I. Oxidative degradation characteristics
II. Quantitative weight losses
III. Compositional analysis
IV. Long term stabilities
V. Flammability properties
VI. Rates of degradation
VII.Decomposition temperatures
VIII.Thermal degradation properties

18. REFERENCE
• Instrumental method of chemical analysis B.K Sharma page
no: 308
• Pharmaceutical drug analysis Ashutosh Kar page no: 194