DISCOVERY 差示扫描量热仪

因为药物晶体具有很好的储存稳定性，药物公司在新药物配方中倾向采用结晶化合物。然而经常碰到的问题是药物存在多种结晶形式，即通常所说得多晶型。由于多晶型的每种晶型的物理性质、比如分散速率和生物活性有很大的不同，因此控制结晶的形势和含量显得十分重要。

DSC是在定义的气氛下测量样品发生转变时的温度与热流随温度或时间变化的函数关系；MDSC是在传统DSC上的提高，它将总的热流分解成可逆热流(热容)和不可逆(动力学)组分。

TA仪器的调制DSC技术，是在传统DSC线性变温程序上叠加一个正弦变化，从而直接测量热流和比热。采用Fourier 转换，热流实时被分解为热容成份和动力学成份。在MDSC®中，DSC的热流称为总热流，热容成份为可逆热流，动力学成份为不可逆热流。总热流信号包含所有的热转化信息，与标准DSC的结果一样。可逆热流中包含玻璃化转变、熔融等信息，不可逆热流中包含动力学的现象，如固化、挥发、熔融和分解等。 *美国专利 Nos. 5,224,775; 5,248,199; 5,346,306 加拿大专利 No. 2,089,225 日本专利No. 2,966,691 MDSC®技术提供： • 将复杂转变分解为更容易理解的成份 • 检测弱转变和熔化时，提高灵敏度 • 在不损失灵敏度的前提下，提高分辨率 • 直接测量热容 • 更准确的结晶度测量

Modulated DSC (MDSC) can be easily understood by comparing it to its well-established precursor, differential scanning calorimetry (DSC). Conventional DSC is an analytical technique in which the difference in heat flow between a sample and an inert reference is measured as a function of time and temperature as both the sample and reference are subjected to a controlled environment of time, temperature, atmosphere and pressure. The schematic of a typical “heat flux” DSC cell is shown in Figure 1. In this design, a metallic disk (made of constantan alloy) is the primary means of heat transfer to and from the sample and reference. The sample, contained in a metal pan, and the reference (an empty pan) sit on raised platforms formed in the constantan disk. As heat is transferred through the disk, the differential heat flow to the sample and reference is measured by area thermocouples formed by the junction of the constantan disk and chromel wafers which cover the underside of the platforms. Chromel and alumel wires attached to the chromel wafers form thermocouples which directly measure sample temperature. Purge gas is admitted to the sample chamber through an orifice in the heating block wall midway between the raised platforms. The gas is preheated by circulation through the block before entering the sample chamber. The result is a uniform, stable thermal environment which assures excellent baseline flatness and exceptional sensitivity (signal-to-noise). In conventional DSC, the temperature regime seen by the sample and reference is linear heating or cooling at rates from as fast as 200°C/minute to rates as slow as 0°C/minute (isothermal).