Privalov G, Kavina V, Freire E, Privalov P L
Department of Biology, Johns Hopkins University, Baltimore, Maryland 21218, USA.
Anal Biochem. 1995 Nov 20;232(1):79-85. doi: 10.1006/abio.1995.9957.
A precise scanning calorimeter for studying the heat capacity of liquids in a broad temperature range has been developed. By its design and capabilities this calorimeter is the first of a new generation for this type of instrument. This new scanning calorimeter operates differentially, is equipped with a pair of gold capillary cells and semiconductor sensors, and is able to scan up and down in temperature at user-selected rates. This instrument is completely operated by an integrated computer which also provides a full thermodynamic analysis of the results. Its construction does not involve the use of organic compounds, thus eliminating a source of baseline noise that has affected previous calorimeters. The operational temperature range of the instrument can be varied between 0 and 120 degrees C. The gold capillary cells (operational volume 0.8 ml) minimize temperature gradients in the heated/cooled liquid sample and permit easy washing and reloading without air bubbles. These features are crucial for the accuracy of difference heat capacity measurements and determination of the absolute value of the partial heat capacity of solute molecules. The measurements can be performed under an excess constant pressure (up to 3 atm) to prevent formation of gas bubbles and boiling of aqueous solutions above 100 degrees C. The noise level of the recorded heating/cooling power difference is below 50 x 10(-9) W (i.e., below 10 ncal/s) with a response half-time of 5 s. The reproducibility of the baseline without refilling the capillary cells is on the order of 0.5 x 10(-6) W. Reproducibility of the baseline upon refilling the cell is of the same order of magnitude. This provides an accuracy in difference heat capacity determination on the order of 10 mu cal/degrees Kml at a heating rate of 1 degree K/min.
已研制出一种用于在宽温度范围内研究液体热容的精密扫描量热计。从其设计和功能来看，该量热计是此类仪器新一代中的首款。这种新型扫描量热计采用差动操作，配备一对金毛细管池和半导体传感器，能够以用户选定的速率进行温度的上下扫描。该仪器完全由一台集成计算机操作，该计算机还能对结果进行完整的热力学分析。其构造不涉及有机化合物的使用，从而消除了影响以往量热计的基线噪声源。该仪器的工作温度范围可在0至120摄氏度之间变化。金毛细管池（工作体积0.8毫升）可使加热/冷却液体样品中的温度梯度最小化，并便于清洗和重新装填且无气泡。这些特性对于差示热容测量的准确性以及溶质分子偏摩尔热容绝对值的测定至关重要。测量可在过量恒压（高达3个大气压）下进行，以防止形成气泡以及100摄氏度以上水溶液的沸腾。记录的加热/冷却功率差的噪声水平低于50×10⁻⁹瓦（即低于10纳卡/秒），响应半衰期为5秒。不重新装填毛细管池时基线的重现性约为0.5×10⁻⁶瓦。重新装填池后基线的重现性处于同一数量级。这在加热速率为1开尔文/分钟时，差示热容测定的精度约为10微卡/开尔文·毫升。
