A method is described to accurately measure the compressibility of liquids using an analytical ultracentrifuge. The method makes use of very large pressure gradients, which can be generated in the analytical ultracentrifuge at high speeds to induce a maximum compression signal. Taking advantage of the new Optima AUC, which offers 10 micron radial resolution, a novel calibration centerpiece for measuring rotor stretch, and a speed-ramping procedure, even the weak compressibility of liquids like water, typically considered to be incompressible, could be detected. A model using the standard expression for the secant-average bulk modulus describing the relative compression of a liquid in the analytical ultracentrifuge is derived. The model is a function of the loading volume and the hydrostatic pressure generated in the analytical ultracentrifuge, as well as the secant-average bulk modulus. The compressibility of water and toluene were measured and the linear secant-average bulk modulus and meniscus positions were fitted. In addition to the measurement of the compressibility of liquids, applications for this method include an improved prediction of boundary conditions for multi-speed analytical ultracentrifugation experiments to better describe highly heterogeneous systems with analytical speed-ramping procedures, and the prediction of radius-dependent density variations.

描述了一种使用分析超速离心机准确测量液体可压缩性的方法。该方法利用非常大的压力梯度，它可以在分析超速离心机中以高速产生，以产生最大的压缩信号。利用提供 10 微米径向分辨率的新型 Optima AUC、用于测量转子拉伸的新型校准中心部件和加速程序，甚至可以检测到通常被认为不可压缩的水等液体的微弱可压缩性。推导出使用正割平均体积模量的标准表达式的模型，该模型描述了分析型超速离心机中液体的相对压缩。该模型是加载体积和分析超速离心机中产生的静水压力的函数，以及割线平均体积模量。测量了水和甲苯的可压缩性，并拟合了线性正割平均体积模量和弯液面位置。除了测量液体的可压缩性外，该方法的应用还包括改进多速分析超速离心实验的边界条件预测，以更好地描述具有分析速度斜坡程序的高度异质系统，以及预测半径相关的密度变化。