What is osmolality?
Simply put, osmolality is a measurement of the total number of solutes in a liquid solution expressed in osmoles of solute particles per kilogram of solvent. When any solute is dissolved in a solvent, four of the colligative properties of the solution are affected in a roughly linear response to the concentration of solute added:
The resulting changes in these properties are not proportional to the weight, size or shape of the dissolved particles, but only to their molal concentration. Osmolality therefore is an ideal measurement to estimate the total concentration of solutes in a near limitless variety of liquid sample matrices, including blood, serum, plasma, urine, milk, cell culture media and almost all forms of aqueous based solutions.