Copyright 2018, InnovaPrep LLC
Patented
https://www.innovaprep.com/patents
8
2.2
W
ET
F
OAM
E
LUTION
The Wet Foam Elution process is much more efficient than liquid rinsing for the following reasons:
Volume Expansion
When rinsing a filter with liquid, most of the liquid volume is used to fill the dead space inside the filter housing; or
inner bore of the membrane for hollow fiber tips. Thus, only a small portion of the fluid is actually in contact with the
filter surface. This can be minimized to an extent by reducing the cross-sectional area of the fluid path across the filter,
but a large portion of the liquid is still underutilized. Foam, however, is 80-90% gas, which fills the empty space without
contributing to the final sample volume.
Increased Viscosity
Liquid has a tendency toward “channeling” when flowing across a surface; that is, there is an area of high flow in the
center of the fluid path while the portion of flow in contact with the filter surface is much slower. The higher viscosity
of foam prevents channeling and creates a more uniform flow across the filter surface.
Bubble Dynamics
The micro-bubbles in the foam behave as deformable solids. As they travel across the surface of the filter they move
as a rigid body with a narrow lubricating layer, effectively squeegeeing the particles off of the surface.
Exfoliating Action
As the micro-bubbles in the foam impact against each other and burst, the turbulence and energy produced helps to
lift particles that are adhering to the membrane.
2.3
F
OAM
G
ENERATION
The Wet Foam Elution™ process requires very specific high-quality foam in order to be effective. The elution fluid is
composed of water, a low concentration surfactant (usually less than 0.1%), and a pH buffer. This solution is carbonated
with carbon dioxide (CO
2
) gas. During the elution process, the fluid passes through a valve to a low pressure environment,
causing the dissolved CO
2
to expand and come out of solution to form microbubbles. These micro-bubbles increase the
volume of the fluid sixfold or more.
An additional benefit of Wet Foam Elution is the clean buffer exchange. In many situations, the starting sample matrix is
not the most desirable for the chosen analysis method. Wet Foam Elution allows the user to select the fluid that the
particles will be suspended in after concentration, which reduces inhibition and maximizes the chances of detection.
2.4
CP
F
ILTER
T
IPS
For selecting the proper CPT please refer to the filter selection matrix presented in Table 2.1.
