Freezing point depression osmometers are the industry-preferred solution in clinical chemistry, pharmaceutical, and quality control labs. There are a number of logical reasons for this:
- All of the advantages and none of the disadvantages of other forms of osmometry– Membrane osmometry is limited by the lack of a perfect semi-permeable membrane; and vapor pressure osmometry is affected by volatile compounds exerting their own vapor pressure – a major drawback in the clinical chemistry lab setting.
- Freezing point measurements are fast and accurate – Test times are around 2 minutes and repeatability is in the range of ± 2 mOsm/kg H2O.
- Small sample size requirements – Typical sample volumes are in the µL range, this is advantageous for sample-limited and clinical lab settings.
- Simple to use – Requires very little knowledge or scientific background to operate systems and achieve good results.
- Limitless applicability and utility – Freezing point osmometers work well with almost any liquid matrix and are found in nearly every laboratory where osmolality testing is required.
- The most widely referenced and practiced technique for osmolality testing – Freezing point osmometers have been commercially available for over 50 years and are the most widely referenced technology for osmolality testing.
Types of Osmometers
An osmometer is a device for measuring the osmotic strength of a solution, colloid or compound. There are three major types of osmometers commercially available, each leveraging a particular colligative property to achieve their analytical results:
Freezing Point Osmometers – determine the osmotic strength of solution by utilizing freezing point depression
Vapor Pressure Osmometers – determine the concentration of osmotically active particles that reduce the vapor pressure of the solution
Membrane Osmometers – measure the osmotic pressure of a solution separated by a semi-permeable membrane
|Freezing Point Osmometry (FPO)||FPO provides rapid and inexpensive results with the industry preferred freezing point method. Requires small sample size and ideally suited for most biological and aqueous applications.|
|Vapor Pressure Osmometry (VPO)||VPO provides fast an inexpensive measurements requiring a small sample size, although not as fast or reliable as FPO. Volatile solutes are not amenable to VPO limiting its utility in many applications|
|Membrane Osmometry (MO)||MO provides a direct measurement of osmolality and is suitable for high molality and colloidal samples. Long analysis time and requires a large sample volume. Not applicable for small molecule applications.|