Osmometer
Measures the osmolality of a solution, the total concentration of dissolved particles, usually by how much the solution's freezing point is lowered. Used for injections, eye drops and infusion fluids.
- Pharmaceutical
- Biotech
- Clinical laboratories
- Food & beverage
- Academic research
Test your Osmometer knowledge
Multiple-choice questions
Pick an answer to see whether you are right and why.
Q1. Osmolality is expressed in:
basicQ2. Typical osmolality of human plasma is about:
basicQ3. A freezing-point osmometer measures osmolality using:
intermediateQ4. A solution freezes at −0.558 °C. Using 1.86 °C per osmol/kg, its osmolality is about:
intermediateQ5. What usually causes a 'pre-freeze' error?
intermediateQ6. Why does 0.9% sodium chloride measure about 286 mOsm/kg rather than the calculated 308?
advanced
Viva questions
Think of your answer first, then open it to compare.
1. What is the difference between osmolality and osmolarity?
Osmolality is osmoles per kilogram of water and is what an osmometer measures. Osmolarity is osmoles per litre of solution and is usually calculated. For dilute solutions the values are close but not the same.
2. Why is osmolality important for injections and eye drops?
A strongly hypotonic or hypertonic product can damage cells, cause pain, irritation or haemolysis. Products close to the osmolality of body fluids (typically around 280–300 mOsm/kg) are better tolerated.
3. Why must the sample be measured soon after pipetting?
Water evaporates from the small sample, raising the concentration and the osmolality. Measuring promptly, with covered tubes, avoids this error.
Keep every Osmometer in control: usage logs, calibration and maintenance schedules, and automatic blocking of overdue instruments.