1. DIFFERENTIAL THERMAL ANALYSIS (DTA)
Presented By
Mr. Shaise Jacob
Faculty
Dept. of Pharmaceutical Analysis
Nirmala College of Pharmacy
Muvattupuzha, Kerala
India
E mail -

2. Thermal Analysis Techniques
When a material is heated its structural and chemical composition can undergo changes such as fusion, melting, crystallization, oxidation, decomposition, transition, expansion and sintering.
Using Thermal Analysis such changes can be monitored in every atmosphere of interest. The obtained information is very useful in both quality control and problem solving.

3. Types of thermal analysis
TG (Thermogravimetric) analysis:
weight
DTA (Differential Thermal Analysis): temperature
DSC (Differential ScanningCalorimetry): temperature

4. In Differential Thermal Analysis, the temperature difference that develops
between a sample and an inert reference material is measured, when both are subjected
to identical heat - treatments.
The related technique of Differential Scanning Calorimetry relies on differences in energy required to maintain the sample and reference at an identical temperature.

5. Thermogravimetry (TG)
Thermogravimetry is the measurement of the mass of a sample as the temperature increases. This method is useful for determining sample purity and water, carbonate, and organic content; and for studying decomposition reactions.

6. INTRODUCTION
This is a comparison method
Analytical method for recording the difference in temperature (∆T) b/w a substance and an inert reference material as a function of temperature or time
Any transformation – change in specific heat or an enthaply of transition can be detected by DTA

7. In DTA both test sample & an inert reference material (alumina) – controlled heating or cooling programming
If zero temperature difference b/w sample & reference material – sample does not undergo any chemical or physical change.
If any reaction takes place temperature difference (∆T) will occur b/w sample & reference material

8. A DTA curve can be used as a finger print for identification purposes, for example,
in the study of clays where the structural similarity of different forms renders diffraction experiments difficult to interpret.

9. Sharp Endothermic – changes in crystallanity or fusion
∆T VS Temp.
Sharp Endothermic – changes in crystallanity or fusion
Broad endotherms - dehydration reaction
Physical changes usually result in endothermic curves
Chemical reactions are exothermic

10. Apparatus
The key features of a differential thermal analysis kit are as follows
1. Sample holder comprising thermocouples, sample containers and a ceramic or metallic
block.
2. Furnace.
3. Temperature programmer.
4. Recording system.

14. Heart of the analysis – heating block
Identical pair of cavities for the sample, ref. material
Whole unit is set in an oven- control pressure
Thermocouple is place directly in contact with the sample and another in contact with the reference
Temp.of the block is raised, the temperature of the sample & reference follow
Zero temp. difference – no physical or chemical change
If any reaction – difference in ∆T

17. Differential Thermal Analysis
advantages:
instruments can be used at very high temperatures
instruments are highly sensitive
characteristic transition or reaction temperatures can be accurately determined
disadvantages:
uncertainty of heats of fusion, transition, or reaction estimations is 20-50%
DTA

18. Factors affect results in DTA
Sample weight
Particle size
Heating rate
Atmospheric conditions
Conditions of sample packing into dishes

20. Applications
Quantitative identification and purity assessment of materials are accomplished by comparing the DTA curve of sample to that of a reference curve
Impurities may be detected by depression of the M.P