Differential scanning calorimetry

basic introduction

Differential Scanning Calorimetry (DSC) is a technique for measuring the relationship between the power difference between a feed material and a reference and temperature at a programmed temperature.
The DSC is similar to the DTA instrument, except that two sets of compensation heating wires are placed under the sample and reference container. When the temperature difference ΔT occurs between the sample and the reference during heating, the difference is passed. The thermal amplifier circuit and the differential heat compensation amplifier change the current flowing into the compensation heating wire. When the sample absorbs heat, the compensation amplifier immediately increases the current on one side of the sample; conversely, when the sample releases heat, the reference is made. Increased current on one side of the object

Differential scanning calorimetry

Until the heat balance on both sides, the temperature difference ΔT disappears. In other words, the change in heat that occurs during the thermal reaction of the sample is compensated for by the timely input of electrical power. Therefore, the actual difference between the thermal power of the two electrothermal compensations under the sample and the reference is recorded as a function of time t. . If the heating rate is constant, the difference between the recorded thermal power and the temperature T is recorded.

Recording curve

The curve recorded by the differential scanning calorimeter is called the DSC curve, which is the rate at which the sample absorbs or exotherms, that is, the heat flow rate dH/dt (units of millijoules per second) is plotted on the ordinate, and the temperature T or time t is horizontal. Coordinates, a variety of thermodynamic and kinetic parameters can be determined, such as specific heat capacity, heat of reaction, heat of transition, phase diagram, reaction rate, crystallization rate, polymer crystallinity, sample purity, and the like. The method has a wide temperature range (-175~725 °C), high resolution, and low sample consumption. Suitable for inorganic, organic compounds and pharmaceutical analysis.

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Classification introduction

1.

Power compensated DSC

2. Heat flow DSC
DSC is a dynamic calorimetry technology. The important corrections for DSC instruments are temperature correction and calorimetry.

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Application range

Differential scanning calorimetry (DSC) is a thermal analysis method. The difference in power (eg, in the form of heat) input to the sample and reference is measured at program-controlled temperature versus temperature. The curve recorded by the differential scanning calorimeter is called the DSC curve, which is the rate at which the sample absorbs or exotherms, that is, the heat flow rate dH/dt (units of millijoules per second) is plotted on the ordinate, and the temperature T or time t is horizontal. Coordinates, a variety of thermodynamic and kinetic parameters can be determined, such as specific heat capacity, heat of reaction, heat of transition, phase diagram, reaction rate, crystallization rate, polymer crystallinity, sample purity, and the like. The method has a wide temperature range (-175~725 °C), high resolution, and low sample consumption. Suitable for inorganic, organic compounds and pharmaceutical analysis. In recent years, the use of thermal analysis methods to determine the purity of drugs has been reported in the United States, the United States Pharmacopoeia has also measured the purity of the drug to determine the drug [1], indicating a good prospects for the method. The following is a brief list of some of the applications of DSC in drug analysis.