Osmometry is the analytical method of measuring osmotic pressure (π) and related colligative properties. Accurately measuring π is essential for applications that use osmosis, including drug delivery systems and water filtration methods such as forward osmosis. The three most common forms of directly or indirectly measuring π are vapour pressure osmometry (VPO), freezing point osmometry (FPO), and direct membrane osmometry (DMO). In this report, the performance of VPO, FPO, and DMO are compared for various aqueous solutions, including small molecule and polymer solutes, and potentially more difficult samples such as concentrated, carbonated, or viscous solutions. Potential problems with each of the three methods are examined. Good practices can avoid inaccuracies in DMO due to external concentration polarization and solute diffusion through the membrane. Similarly, it is important to be aware of and avoid weaknesses in VPO and FPO in order to obtain reliable results. Even with care, however, the three methods still give different values of π for concentrated aqueous solutions.

渗透压法是测量渗透压 ( π ) 和相关依数性质的分析方法。准确测量π对于使用渗透的应用至关重要，包括药物输送系统和水过滤方法（如正向渗透）。直接或间接测量π的三种最常见形式渗透压法 (VPO)、冰点渗透压法 (FPO) 和直接膜渗透压法 (DMO)。在本报告中，比较了 VPO、FPO 和 DMO 对各种水溶液的性能，包括小分子和聚合物溶质，以及可能更难的样品，如浓缩溶液、碳酸溶液或粘性溶液。对这三种方法中的每一种的潜在问题进行了检查。良好的实践可以避免由于外部浓差极化和溶质通过膜的扩散而导致 DMO 不准确。同样，重要的是要了解并避免 VPO 和 FPO 的弱点，以获得可靠的结果。然而，即使小心翼翼，这三种方法仍然会为浓缩水溶液给出不同的π值。