User Manual
Fig. 3. Optional settings for the 3-way flow valve to obtain optimal performance from the Bio-Dot apparatus.
3.2 Helpful Hints
1. During the assay, do not leave the vacuum on. This may dehydrate the membrane and
may cause halos around the wells. Apply vacuum only until solutions are removed from
the sample wells, then adjust the flow valve so that the unit is exposed to air and
disconnect the vacuum.
2. If some sample wells are not used in a particular assay, those wells must be closed off
to ensure proper vacuum to the wells in use. There are three ways to close off unused
wells. One is to apply a 3% gelatin solution to those wells. Gelatin will clog the
membrane and cut off the vacuum flow to the clogged wells. The second method is to
cover the unused portion of the apparatus with tape to prevent air from moving through
those wells. The third method is to add buffer to the empty wells at each step instead of
sample or wash solutions.
3. If an overnight incubation is desired, adjust the flow valve so that the vacuum manifold
is closed off from both the vacuum and air before applying samples (see Figure 3). In this
configuration, solutions will remain in the sample wells with less than 10% loss of volume
during an overnight incubation. Note that the unit must be kept at a constant temperature
during extended incubations. If the unit cools more than 10°C (20°F), a partial vacuum will
build inside the unit and drainage will occur.
4. Any particulate in samples or solutions will block the membrane and restrict flow of
solutions through the membrane. For best results, filter or centrifuge samples to remove
particulate matter.
5
Flow valve setting 1.
The vacuum manifold is exposed
to the vacuum source only. Use for
applying vacuum to the Bio-Dot apparatus.
Flow valve Setting 2.
The manifold is exposed to air.
Use for gravity filtration procedures.
Flow valve Setting 3.
The manifold is exposed to both air and
the vacuum. Use this setting for gentle
vacuum applications where the amount of
vacuum is regulated by putting a finger over
the port exposed to the atmosphere.