Osmolality is a measure of a solution’s osmotic concentration, which defines the total number of solute particles within the liquid that contribute to osmotic pressure. This is typically expressed as the number of osmoles (Osm) of solute per kilogram (kg) of solute. When it comes to measuring microscale solutes, such as ions in organic samples, measurements must operate on an order of thousands of times smaller than the osmole. These measurements are routinely conducted using osmometers.
An osmometer measures osmotic concentration on the scale of milliosmoles (mOsm) per unit of weight (mOsm/kg). This provides valuable insights into the osmotic strength and pressure of various colloidal systems. In this blog post, Icon Scientific outlines the working principles of osmometers in more detail.
Principles of Osmometers: Osmolality Vs. Osmolarity
Understanding how osmometers work first requires a basic understanding of the differences between osmolality (mOsm/kg) and osmolarity (mOsm/L). As mentioned, osmolality is a measure of a solution’s particle concentration by weight. Osmolarity is different in that it determines the total number of particles in a solution per unit of volume. The difference between these two properties is often marginal, as in clinical applications, where the physiology of osmotic solutions under examination are mainly aqueous. Yet it is still important to make the distinction when discussing the working principles of osmometers.
There are numerous different osmometer technologies available for determining the osmolality of aqueous samples (freezing point osmometers, vapor pressure osmometers, etc.). While the operating principles vary, they tend to measure osmolality as a function of changes to a constant parameter. In freezing point osmometry, for example, this constant is the freezing point of a solvent. A freezing point osmometer measure changes in a solvent’s freezing point as a function of the total number of solutes. The reason the above distinction is so important is that there is a precise linear correlation between osmolality and the freezing point of a solution.
The same basic principle is true of vapor pressure osmometers, which measure the total osmolality of a biological solution as a function of changes in vapor pressure.
Applications of Osmometers
Osmometers are used in an extremely broad range of application areas, primarily for clinical studies and treatment. They are used to measure the concentration of solutes in various biological samples, from blood plasma to human tears. These measurements can provide a rich array of data to assist in timely diagnoses of various conditions with significantly reduced healthcare costs.
However, there is increasing availability to use osmometry in quality control and assurance of various consumer products. Freezing point osmometers have been used to screen isotonic beverages and determine their veracity against regulated standards. These range from sports drinks to non-alcoholic beer.
Osmometers from Icon Scientific
Icon Scientific supplies a range of freezing-point and vapor pressure osmometers for the determination of the osmolality of a broad range of samples. The K-7400S Semi-Micro Osmometer is a user-friendly system that can provide a rapid determination of the osmolality of aqueous samples in under two minutes. The K-7000, meanwhile, can measure up to four samples simultaneously using mere nano volumes of sample material.
If you would like any more information about the osmometers available from Icon Scientific, simply contact a member of the team today.
ICON Scientific, Inc
