Osmometry is a technique that measures the concentration of solute particles contributing to the osmotic pressure of a solution by measuring its freezing point depression. It works by cooling a sample below -7°C in a cooling bath with stirring until it freezes solid, allowing the osmometer to measure the temperature change and display the osmolarity result. Normal osmolarity ranges are 60-1200 mosm/kg H2O for urine and 280-303 mosm/kg H2O for serum, with increases indicating dehydration or diabetes insipidus and decreases suggesting renal failure.

1. OSMOMETRY

2. •Osmometry is the technique for measuring the
conc. Of solute particles that contribute to the
osmotic pressure of solution
•Osmolarity- measure of osmotically active particles

3. •Principle
Freezing point depression
•components
1. Colling bath maintained at -7◦C
2. Rapid stir mechanism; to initiate freezing of
sample
3. Thermistor probe ; to measure temp. of sample
4. LED display; to show result

4. working
• Sample is first lowered into the cooling bath with
gentle stirring, It is super cooled to a temp. below -7◦C
• When LED display shows sufficient cooling has
occurred , sample is raised above the liquid level of
cooling bath. Gentle stirring changes to vigorous
stirring, which causes freezing of super cooled sample
• Sample freezes to complete solid

5. Normal values
•Urine osmolarity ; 60-1200 mosm/kg of H2O
•Serum osmolarity; 280- 303 mosm/ kg of H2O

6. •Increased osmolarity
•Dehydration
•Diabetes insipidus
•Decreased osmolarity
•Renal failure

7. LED display
sample
Cooling
bath

8. Assignment
Mass spectrophometry