| Purity and quality are the major events in | | | | critical for the accurate measurement of purities |
| pharmaceutical sector. One of the most important | | | | - Measurement of true heat flow rather than |
| tests that can be performed for pharmaceutical | | | | temperature differential for more accurate |
| and organic material is the assessment of its | | | | calorimetric determinations |
| purity by differential scanning calorimetry (DSC) | | | | - Use PRT (platinum resistance thermometer) |
| during in process and finished product drug | | | | temperature sensors rather than thermocouples |
| development. DSC has proven to be a rapid, | | | | for the most accurate and precise measurement |
| accurate, precise and easy-to-use approach for | | | | of sample temperature |
| the assessment of the purity of many different | | | | - Outstanding resolution providing more |
| types of materials. This method depends only on | | | | theoretically correct melting responses (i.e., narrow |
| the physicochemical behavior of the compound. | | | | peak half-width and greater peak intensity) |
| This method is accurate for samples over 98% | | | | - Very high sensitivity |
| pure, but it does not measure impurities which are | | | | - Glass transition and melting point |
| soluble in the solid phase or insoluble in the melt. | | | | - Crystallisation time and temperature |
| Differential Scanning calorimetry | | | | - Heats of melting and crystallization |
| Differential Scanning Calorimetry (DSC) monitors | | | | - Percent crystallinities |
| heat effects associated with phase transitions and | | | | - Oxidative stabilities and heat capacities |
| chemical reactions as a function of temperature. | | | | - Heats of cure and percent cure |
| In a DSC the difference in heat flow to the | | | | - Polymorphism and recyclates and regrinds |
| sample and a reference at the same | | | | - Compositional analysis |
| temperature, is recorded as a function of | | | | - Thermal stabilities and purities |
| temperature. The reference is an inert material | | | | The particle size of the sample also affected its |
| such as alumina, or just an empty aluminum pan. | | | | purity value. The effects could be explained in |
| The temperature of both the sample and | | | | terms of thermal lags, decomposition and |
| reference are increased at a constant rate. The | | | | evaporation during melting or sublimation before |
| heat flow difference can be either positive or | | | | melting. Decrease of particle size may either lead |
| negative. | | | | to low purity values, due to concurrent increase in |
| ?dH/dT= [dH/dT]sample - [dH/dT]reference | | | | structural disorder or to increase in purity values, |
| Here dH/dT is the heat flow measured in mcal | | | | due to the formation of aggregates by |
| sec-1.In an endothermic process, such as most | | | | electrostatic forces. It was concluded that if |
| phase transitions, heat is absorbed and therefore | | | | triturating of sample before subjecting to DSC |
| heat flow to the sample is higher than that of the | | | | analysis causes aggregate formation, purity values |
| reference. Hence ?dH/dT is positive. | | | | which are too high may result. |
| Features and benefits | | | | The purity of an organic substance can be |
| For purity analysis, the power compensated DSC, | | | | estimated by DSC based on the shape and the |
| provides a number of important features and | | | | temperature of the DSC melting endotherm. This |
| benefits for the assessment of the purity of | | | | procedure utilizes the Van’t Hoff equation, |
| pharmaceutical and organic materials: | | | | which is given as: |
| - Very low mass furnaces (1g) for sample side | | | | 1/Fs = [? |
| and reference side providing rapid response times | | | | |