Waters ACQUITY UPC2 - Comparing Supercritical Fluid Properties to those of Other Solvents; System Configurations

November 16, 2016, 715004521 Rev. C
Page 14
1.1.1 Comparing supercritical fluid properties to those of other
solvents
Supercritical CO
2
fluid has a lower viscosity, higher diffusion rate, and no surface tension when
compared to liquid CO
2
. Supercritical CO
2
physical properties are between those of liquids and
gases. Diffusivities of solutes in supercritical CO
2
are by as much as a factor of 10 higher than their
diffusivities in liquid solvents. Because supercritical fluid properties are pressure-dependent near
the critical point, they are highly tunable solvents.
Recommendation: Use only food-grade, or better, house-supplied CO
2
or non-siphon CO
2
at a
flow pressure of 6,205 to 7,584 kPa (62 to 76 bar, 900 to 1100 psi).
1.2 System configurations
The following illustrations show the four core configurations that comprise the ACQUITY UPC
2
system. A system configuration can differ according to the number and type of modules it contains.
For example, if a system includes a mass spectrometer, the system modules can be arranged as
two or three separate stacks.
Table 1–1: Solvent viscosity comparison
Solvent Viscosity range
Supercritical CO
2
fluid 20-100 µPa.s (0.02-0.1 cP)
Liquids 500-1000 µPa.s (0.5-1.0 cP)
Gases 10 µPa.s (0.01 cP)