Osmometers
Osmometers and micro-osmometers (osmotic meters) are devices for measuring the osmolality (osmotic concentration or osmotic strength) of aqueous solutions. Osmolality is defined as the total concentration of all osmotically-active dissolved solutes present in a given volume of solution. Osmolality is usually measured in mOsm/L or Osm/L.
Modern, automated electronic osmometers offer user-programming and digital displays and can analyse very small volumes of samples down to 20µL.
What are the different types of osmometers?
Different types of osmometers are available which work on different operating principles:
- Freezing point osmometers are the industry-preferred models with the greatest accuracy and precision. The freezing point of water is depressed in proportion to the level of dissolved solute
- Vapour pressure osmometers avoid issues associated with high viscosity or suspended particulates that can sometimes interfere with freezing point depression
- Other osmometers based on the principles of specific gravity, refractive index, semipermeable membrane flow or conductivity are less favoured because they are now considered less reliable
- Most osmometers are supplied with a range of calibration standards and reference solutions (osmometer controls) and osmometer accessories.
What are osmometers used for in the lab?
Osmometers are key items of equipment in a range of laboratory environments:
- In clinical chemistry, for testing whole blood, serum, plasma, urine and other body fluids for metabolic and electrolytic disorders and intoxication
- Bioprocess monitoring in the pharmaceutical industry to monitor concentrations at critical points during the manufacturing process
- In organic and inorganic chemistry for determining the average molecular weight of unknown compounds or mixtures, especially polymers
- In other areas of biology, for example analysis of plant saps, hydroponic or cell culture media
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