DIFFERENTIAL SCANNING CALORIMETRY.pptx

Differential Scanning Calorimetry (DSC) is one of the important thermal analytical techniques in which specific physical properties of a material are measures as a function of temperature. It is used both in qualitative and quantitative analysis.
DSC is a technique for measuring the energy necessary to establish a nearly zero temperature difference between a substance and an inert reference material as the two specimens are subjected to identical temperature regimens in an environment heated or cooled at a controlled rate.
This technique was developed by E.S.Watson and M.J.O' Neill in 1964.
The device used to measure this is Calorimeter.
There are two types of DSC systems commonly used:
1. Power compensated DSC
2. Heat -flux DSC
A High resolution of PC-DSC is nowadays widely used known as Hyper DSC.

1. HYPER DIFFERENTIAL SCANNING CALORIMETRY Made By, Nitika M. Pharm 1 st Sem

2. INTRODUCTION Thermal Techniques Thermal analysis includes a group of techniques in which specific physical properties of a material are measured as a function of temperature. Measurements are usually made with increasing temperature, but measurements made with decreasing temperatures are also possible. It is useful in both quantitative an qualitative analysis. Samples may be identified and characterized by qualitative investigations of their thermal behavior. Quantitative results are obtained from changes in weight and enthalpy as the sample is heated. The temperatures of phase changes and reactions as well as heats of reaction are used to determine the purity of materials.

3. Types of Thermal Analysis

4. DIFFERENTIAL SCANNING CALORIMETRY D SC is a technique to establish a nearly zero temperature difference between a sample and reference is measured as a function of temperature when both are heated or cooled at a controlled rate. The technique was developed by E.S. Watson and M.J.O’ Neill in 1964 . The DSC, at present, is the most widely used thermal analysis in the pharmaceutical field. In DSC, since power is measured directly, the curves are used quantitatively for the measurement of the heat of reaction and specific heat etc. Calorimeter- it is a device used for measuring the heat of chemical reactions or physical changes as well as heat capacities.

5. What does DSC measures? DSC measures the amount of energy (heat) absorbed or released by a sample as it is heated or cooled or held at constant temperature. It also performs precise temperature measurements. DSC is used to analyze: Melting point Crystallization Glass transition

6. 1. Glass transition Transition from disordered solid to liquid. Observed in glassy solids. Tg – glass transition temperature. 2. Crystallization Material can crystallize. Tc- crystallization temperature. 3. Melting Ordered to disordered transition. Tm- melting temperature.

7. Principles of DSC The difference in heat supplied to the sample, and the reference material per unit time is recorded and plotted as dH/dt vs the average temperature to which the sample and reference to be raised. Endothermic heat flow Heat flows into the sample (energy required) as a result of either heat capacity (heating) or some endothermic process (glass transition, melting, evaporation, etc.). Upward peak in thermogram. Exothermic heat flow heat flows out of the sample (energy released) as a result of either heat capacity (cooling) or some exothermic process (crystallization, oxidation, etc.). Downward peak in thermogram.

8. INSTRUMENTATION HEAT-FLUX DSC POWER-COMPENSATION DSC Sample holders - platinum, aluminum and stainless steel. Sample holders- platinum, aluminum and stainless-steel pans. Sensors - temperature sensors. Usually thermocouples which are same for both sample and reference. Sensors - platinum resistance thermocouple. Separate sensors and heaters for both sample and reference. Furnace - one block for both reference and sample cell. Furnace - separate block for both reference and sample cell. Amplifier- to amplify the signals. Amplifier- to amplify the signals. Recorder- provides graph. Recorder- provides graph.

9. HEAT-FLUX DSC In heat-flux DSC, the difference in heat flow into the sample and reference is measured while the sample temperature is changed at a constant rate . In it, the sample and reference in separate containers are placed on separate platforms which settle on a heated metal disc usually made up of Cu-Ni alloy. Thermocouple are used for monitoring the heat flow from the metal disc to the sample and reference. Inert gas is provided in the system.

10. SCHEMATIC DIAGRAM OF DSC

11. POWER-COMPENSATION DSC In power-compensated DSC, the temperatures of the sample and reference are kept equal to each other while both temperatures are increased or decreased linearly. It has lower sensitivity than heat-flux DSC, but its response time is more rapid . It has two independent furnaces- one for heating sample and other for heating reference. The furnaces are inserted into a large temperature control heat sink . The power supply is varied which is required to ensure that ΔT= 0 at all times . (temperature is constant). A thermogram is then produced by noting the difference in power supplied to the two heaters (ΔE).

12. HYPER DSC The high resolution of PC-DSC or new type of power-compensation DSC provides the best results for an analysis of melting and crystallization of metals or detection of glass transition temperature (Tg) in medications. Fast scan DSC has the ability to perform valid heat flow measurements with fast linear controlled rates especially by cooling, where the rates are higher than classical PC-DSC.. The benefits of such devices are increased sensitivity at higher rates (which enables a better study of kinetics in the process), suppression of undesired transformation etc. It empowers the superior investigation of energy. This method is particularly appropriate for pharmaceutical industry for testing medicaments at different temperatures where fast heating rates are necessary to avoid other unwanted reactions.

13. APPLICATIONS OF DSC Enhanced analysis of thermal transitions. Detection of low-level amorphous content. Detection of “true” melting points. Detection of low energy transitions. Identification of substance.

14. REFERENCES Willard; Merritt; “Instrumental Methods of Analysis”; 7 th Edition; page no.- 761-762. Skoog D.A; Crouch S.R; Holler F.J; “Principles of Instrumental Analysis”; page no.- 982-984. Kamboj P.C.; Pharmaceutical Analysis; Volume-2; page no.- 984-989. Kodre KV, Attarde SR; “Differential Scanning Calorimetry: A Review ”; Research and Reviews: Journal of Pharmaceutical Analysis ; 2014. Ayo Amarachi; Differential Scanning Calorimetry: A Review; International Journal of Applied Biology and Pharmaceutical Technology; Volume-1; 2020.

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