The Osmosis Unit

26 Cotlands Park, Longniddry East Lothian Scotland EH32 0QX

44 (0)1875 852761                 

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Colloid Osmotic Pressure Measurement

COP  at 1, 3, 10,30,50 and 100 K Daltons  


The Osmosis Unit had provided COP analysis to several plasma expander manufacturers. This has been for the development and stability testing of new plasma expanders and for routine manufacturing product quality control.


COP measurement has been provided for research studies at the Hammersmith, Harefield, Brompton,  Exeter and the Eastern General Hospital in Edinburgh.


The COP is the pressure generated across a semi-permeable membrane separating two solutions, one of which contains particles too large to pass through the pores in the membrane. The following figure describes how a colloid osmotic pressure osmometer works.

Injection of the test solution into the chamber above the membrane increases the osmotic pressure in this compartment. This draws fluid out of the transducer compartment reducing the pressure on this side of the membrane. This reduction in pressure is measured by the transducer, which is digitally displayed on the control panel.

The instruments used at The Osmosis Unit are Gonotec Osmomat 050 colloid pressure osmometers. COPís are measured using a range of pore sizes from 1000, to 100,000 Dalton molecular weight cutoffs. Most medical research presently quotes COP10K, i.e. membrane osmotic pressures measured on a 10,000 Dalton membrane. The Osmosis Unit is unique in being able to measure this parameter at a range of pore sizes.

For further information on COP and its role in blood pressure click the following links

Pulse Reverse Osmosis

Therapeutic significance of Pulse reverse Osmosis



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Last modified: 07/05/06