Vapor pressure osmometiy

Vapor-pressure osmometiy is, from its name, compared with membrane osmometry by considering the vapor phase to act like the semipermeable membrane, however, from its principles it is based on vapor pressure lowering or boiling temperature elevation. Since the direct measure of vapor pressure lowering of dilute polymer solutions is impractical because of the extreme sensitivity that is required, VPO is in widespread use for oligomer solutions (M less than 20,000 g/mol) by employing the thermoelectric method as developed by Hill in 1930. In the thermoelectric method, two matched temperature-sensitive thermistors are placed in a chamber that is thermostated to the measuring temperature and where the atmosphere is saturated with solvent vapor. If drops of pure solvent are placed on both thermistors, the thermistors will be at the same temperature (zero point calibration). If a solution drop is placed on one thermistor, a temperature difference AT occurs which is caused by condensation of solvent vapor onto the solution drop. From equihbrixun thermodynamics follows that this temperature increase has its theoretical limit when the vapor pressure of... 

Size Exclusion Chromatography SEC Orthogonal Chromatography OC Vapor Pressure Osmometiy VPO Field Flow Fractionation FFF Spectroscopic Methods... 

Vapor-pressure osmometiy is, from its name, compared with membrane osmometry by considering the vapor phase to act like the semipermeable membrane, however, from its principles it is based on vapor pressure lowering or boihng temperature elevation. Since the direct measure of vapor pressure lowering of dilute polymer solutions is impractical... 

---