DIFFERENTIAL THERMAL ANALYSIS (DTA), ppt

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DIFFERENTIAL THERMAL ANALYSIS (DTA), ppt

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DIFFERENTIAL THERMAL ANALYSIS (DTA), ppt

  1. 1. DIFFERENTIAL THERMAL ANALYSIS (DTA) Presented By Mr. Shaise Jacob Faculty Dept. of Pharmaceutical Analysis Nirmala College of Pharmacy Muvattupuzha, Kerala India E mail - [email_address]
  2. 2. Thermal Analysis Techniques <ul><li>When a material is heated its structural and chemical composition can undergo changes such as fusion, melting, crystallization, oxidation, decomposition, transition, expansion and sintering. </li></ul><ul><li>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. </li></ul>
  3. 3. Types of thermal analysis <ul><li>TG (Thermogravimetric) analysis: </li></ul><ul><li>weight </li></ul><ul><li>DTA (Differential Thermal Analysis): temperature </li></ul><ul><li>DSC (Differential ScanningCalorimetry): temperature </li></ul>
  4. 4. <ul><li>In Differential Thermal Analysis , the temperature difference that develops </li></ul><ul><li>between a sample and an inert reference material is measured, when both are subjected </li></ul><ul><li>to identical heat - treatments . </li></ul><ul><li>The related technique of Differential Scanning Calorimetry relies on differences in energy required to maintain the sample and reference at an identical temperature. </li></ul>
  5. 5. Thermogravimetry (TG) <ul><li>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. </li></ul>
  6. 6. INTRODUCTION <ul><li>This is a comparison method </li></ul><ul><li>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 </li></ul><ul><li>Any transformation – change in specific heat or an enthaply of transition can be detected by DTA </li></ul>
  7. 7. <ul><li>In DTA both test sample & an inert reference material (alumina) – controlled heating or cooling programming </li></ul><ul><li>If zero temperature difference b/w sample & reference material – sample does not undergo any chemical or physical change. </li></ul><ul><li>If any reaction takes place temperature difference (∆T) will occur b/w sample & reference material </li></ul>
  8. 8. <ul><li>A DTA curve can be used as a finger print for identification purposes, for example, </li></ul><ul><li>in the study of clays where the structural similarity of different forms renders diffraction experiments difficult to interpret. </li></ul>
  9. 9. <ul><li>∆ T VS Temp. </li></ul><ul><li>Sharp Endothermic – changes in crystallanity or fusion </li></ul><ul><li>Broad endotherms - dehydration reaction </li></ul><ul><li>Physical changes usually result in endothermic curves </li></ul><ul><li>Chemical reactions are exothermic </li></ul>
  10. 10. Apparatus <ul><li>The key features of a differential thermal analysis kit are as follows </li></ul><ul><li>1. Sample holder comprising thermocouples, sample containers and a ceramic or metallic </li></ul><ul><li>block. </li></ul><ul><li>2. Furnace. </li></ul><ul><li>3. Temperature programmer. </li></ul><ul><li>4. Recording system. </li></ul>
  11. 14. <ul><li>Heart of the analysis – heating block </li></ul><ul><li>Identical pair of cavities for the sample, ref. material </li></ul><ul><li>Whole unit is set in an oven- control pressure </li></ul><ul><li>Thermocouple is place directly in contact with the sample and another in contact with the reference </li></ul><ul><li>Temp.of the block is raised, the temperature of the sample & reference follow </li></ul><ul><li>Zero temp. difference – no physical or chemical change </li></ul><ul><li>If any reaction – difference in ∆T </li></ul>
  12. 17. Differential Thermal Analysis <ul><li>advantages: </li></ul><ul><li>instruments can be used at very high temperatures </li></ul><ul><li>instruments are highly sensitive </li></ul><ul><li>characteristic transition or reaction temperatures can be accurately determined </li></ul><ul><li>disadvantages: </li></ul><ul><li>uncertainty of heats of fusion, transition, or reaction estimations is 20-50% </li></ul>DTA
  13. 18. Factors affect results in DTA <ul><li>Sample weight </li></ul><ul><li>Particle size </li></ul><ul><li>Heating rate </li></ul><ul><li>Atmospheric conditions </li></ul><ul><li>Conditions of sample packing into dishes </li></ul>
  14. 20. Applications <ul><li>Quantitative identification and purity assessment of materials are accomplished by comparing the DTA curve of sample to that of a reference curve </li></ul><ul><li>Impurities may be detected by depression of the M.P </li></ul>

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