Osmolality

The concentration of dissolved particles in a solution, which determines how strongly it draws water across membranes. It is a specification for injectable products, which are usually formulated near physiological levels, and a control parameter in cell culture, where feeds and base additions raise osmolality and stress the cells. The Japanese word literally means osmotic pressure, but results are usually reported as osmolality in mOsm/kg, measured by freezing-point depression. Japanese Pharmacopoeia monographs often express it as an osmotic pressure ratio to physiological saline instead.