DTA

1. DIFFERENTIAL THERMAL ANALYSIS
AND IT’S PHARMACEUTICAL
APPLICATION
Presented By,
J .PRAKASH
M.Pharm Ist sem
Department of pharmaceutical Analysis
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2. THERMAL ANALYSIS
 A group of technique in which physical property of substance or its reaction product is measured
as function of temperature whilst the substance is subjected to a controlled temperature
 Physical properties include –mass, temperature, enthalpy, dimension, dynamic characteristics and
others for measured techniques of thermal analysis.
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3.  Endothermic reaction is any chemical reaction than absorbs the heat from its surrounding. The
absorbed energy provides the activation energy for the reaction to occur.
 The physical properties include fusion, vaporization, sublimation, absorption, and desorption.
 Exothermic reaction is a process in which the heat is evolved from the sample, thus causing its
temperature to rise.
 The physical properties include adsorption and crystallization
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4. METHODS
 Thermo gravimetric analysis (TG)
 Differential Thermal Analysis (DTA)
 Differential Scanning Calorimetry (DSC)
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5.  THERMOGRAVIMETRIC ANALYSIS:
The mass of a sample in a controlled atmosphere is recorded continuously as a function of
temperature or time as the temperature of sample is increased. A plot of mass percentage as a
function of time is called thermogram or thermal decomposition curve.
 DIFFERENTIAL SCANNING CALORIMETRY (DSC):
It is a thermal technique in which difference in heat flow into substance and reference are
measured as function of sample temperature while two are subjected to a controlled temperature
program.
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6. DIFFERENTIAL THERMAL ANALYSIS:
 It is a technique in which the difference in temperature (ΔT) between a substance and reference
material is measured as a function of temperature while the substance and reference material are
subjected to controlled temperature program.
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7. Instrumentation
Simply this instrument consists of
 Sample holder comprising thermocouples, samples containers and a ceramic or metallic block
 Furnace
 Temperature programmer
 Recording system
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9.  A schematic of the furnace compartment of a differential thermal analyzer. A few milligrams of the
sample (S) and an inert reference substance (R) are contained in small aluminum dishes located
above sample and reference thermocouples in an electrically heated furnace.
 The reference material is an inert substance such as alumina, silicon carbide, or glass beads
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10. General Principles
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11.  The glass transition temperature Tg is the characteristic temperature at which glassy amorphous
polymers become flexible or rubber- like because of the onset of the concerted motion of large
segments of the polymer molecules
 Two maxima and a minimum are observed in the thermogram. The two maxima are the result of
exothermic processes in which heat is evolved from the sample, thus causing its temperature to rise
 The minimum labeled “melting” is the result of an endothermic process in which heat is absorbed
by the analyte.
 Crystal formation is responsible for the first exothermic peak.
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12.  The third peak is exothermic and is encountered only if the heating is performed in the presence of
air or oxygen. This peak is the result of the exothermic oxidation of the polymer.
 The final negative change in ΔT results from the endothermic decomposition of the polymer to
produce a variety of products. DTA peaks result from both physical changes and chemical reactions
induced by Temperature changes in the sample.
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13. Applications of DTA
 DTA is considered a qualitative technique. Although able to measure the temperatures at which
various changes occur, DTA is unable to measure the energy associated with each event.
 DTA is a widely used tool for studying and characterizing polymers.
 This illustrates the types of physical and chemical changes in polymeric materials that can be
studied by differential thermal methods.
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14.  DTA is also widely used in the ceramics and metals industry. The technique is capable of studying
high-temperature processes (up to 2400°C for some units) and relatively large sample sizes
(hundreds of milligrams).
 DTA is used to study decomposition temperatures, phase transitions, melting and crystallization
points, and thermal stability.
 An important use of DTA is for the generation of phase diagrams and the study of phase transitions
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15. A differential thermogram of sulfur,
the peak at 113°C corresponds to the solid-phase change
The peak at 124°C corresponds to the melting point of the element.
Liquid sulfur is known to exist in at least three forms, and the peak at 179°C apparently
involves these transitions
the peak at 446°C corresponds to the boiling point of sulfur.
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16. • The DTA method also provides a simple and accurate way of determining the
melting, boiling, and decomposition points of organic compounds.
• thermograms for benzoic acid at atmospheric pressure (A) and at 13.79 bar
(B).
• The lower temperature peak corresponds to the melting point and the
second peak to the boiling point of the acid
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17. Advantages
 Instruments can be used at very high temperatures.
 Instruments are highly sensitive.
 Characteristic transition or reaction temperatures can be accurately determined.
Disadvantages
 Uncertainly of heats of fusion, transition, or reaction estimations is 20-50%
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18. FACTORS AFFECT RESULTS IN DTA
 Sample weight
 Particle size
 Heating rate
 Atmospheric conditions
 Conditions of sample packing into dishes
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19. Sample weight
 The amount of sample taken is effect in the DTA curve change in peak size and position, the
amount of sample mass must be standardized
Particle size
 The particles size effect in curves reproducibility, the irreproducible curves are solved by using small
amount of sample and it must be in uniform particle size
Heating rate
 The change in heating rate produce change in peak size and position, it is corrected by using a low
heating rate
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20. Atmospheric conditions
 The sample cell is surrounded by the atmospheric air, it effects change in the curve, inert gas
allowed to flow to solve this problem.
Conditions of sample packing into dishes
 The packing density effect on the reproducibility of the curves and the sample container effect on
change in peak. The conditions of sample packing into dishes are standardized to solve this
problem.
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21. Thermal Analysis Study of Antihypertensive
Drug Telmisartan
Method:
 DTA Analysis were made using simultaneous TG-DTA apparatus thermal analyzer (Shimadzu DTG-
60H).
 The experiments were performed between ambient and 1000 °C.
 The temperature program had a heating rate 10 °C/min.
 Dry nitrogen at a low rate of 30 ML/min was used as the purge gas.
 The sample mass was kept in the range of 5 mg. α-Al2O3 was used as the reference material.
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• DTA curve of Telmisartan shows an endothermic flattened peak with its maximum at
456.63 °C. The main thermal decomposition reaction is endothermic peaks
• Exothermic peaks at 569.27 °C and 610.90 °C may be due to the pyrolysis of the
compound.
• the compound has an endothermic reaction which is not accompanied by weight loss, the
reaction has its maximum at 265.84 °C. This reaction is endothermic and may be attributed
to melting of the compound.

23. CONCLUSION
 Differential thermal analysis is a method of determining the temperature difference
between sample and reference materials, it can give about the phase properties of a
material at different temperatures. The information obtained by the DTA have great
benefit to industries, hence it’s widespread use.
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24. REFERENCES
 Principles of Instrumental Analysis Seventh Edition by skoog, holler and crouch
 www.slideshare.net
 Advanced Pharmaceutical Bulletin, Refaat Ahmed Saber, Ali Kamal Attia, Waheed Mohamed
Salem 2014, 4(3), 283-287
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