- 137 -
Q.
How is the particle concentration determined?
A.
When running in AutoImage Mode, the camera is imaging the field of view at regular intervals.
In this case, the number of camera images collected multiplied by the volume of each field of view
image (length and width of the field of view times the depth of the flow cell), provides the total volume
of the fluid that was "sampled" by the instrument. The particle concentration is the number of particles
divided by the volume
imaged; if the sample fluid was diluted or concentrated, and/or non-sample fluid
was used to prime the system, the concentration is adjusted to be in terms of the original sample. When
running in Trigger Mode where the camera takes an image only if a fluorescence and/or light scatter
threshold is exceeded, two values provide the information necessary in order to calculate particle
concentration: 1) the ratio of the field of view width to the flow cell width; 2) the number of milliliters
analyzed. Note that VisualSpreadsheet makes the assumption that the particles are distributed
uniformly across the flow cell in calculating the concentration in Trigger Mode.
Q.
How does the FlowCAM determine particle diameter?
A.
There are two ways that the software calculates diameter, Area Based Diameter (ABD) and
Equivalent Spherical Diameter (ESD).
ABD (Area Based Diameter)
is the diameter of the circle with
an area that is equal to the ABD Area of the particle. This diameter can also be thought of as the
diameter of the circle obtained by arranging the pixels that comprise the
thresholded particle in a solid
circle.
ESD (Equivalent Spherical Diameter)
is the mean feret measurement of the particle based on
36 sample measurements (conducted every 5°).
Q.
Should I pre-filter my sample?
A.
If the sample contains a significant number of particles that have a diameter greater than the
width of the flow cell, then the sample will need to be filtered to prevent clogging of the flow cell.
Q.
What are the different lasers and PMT/Filter sets that are available for use with the
FlowCAM?
A.
The laser and PMT/Filter set is specified at the time of purchase for each FlowCAM. However,
depending on the model of the FlowCAM, it may be possible to upgrade or use other lasers and/or filter
sets. At this time, Fluid Imaging Technologies, Inc. builds FlowCAMs equipped with 532 nm or
488
nm lasers. The PMT/Filter sets available include Red/Orange [>650/575±15] and Red/Green
[>650/525±15].
Q.
When viewing the flow cell, I can see small particles that appear to be on the glass and
some that don’t move when the flow cell is adjusted. How do I remove these particles?
A.
These small particles are typically dust and contamination that can be found on the inside and
outside of the flow cells and on the outside of the objective lens. You can use high grade acetone or lens
cleaning solution to clean the objectives and flow cells. Only use specially designed lens paper to avoid
scratching any of the glass surfaces. Immediately after use, rinse the funnel and flow cell with deionized
or distilled water. If necessary, precede this rinse with an appropriate solvent or surfactant in order to
remove the particles. The rinse will help keep the flow cells clear and free from contamination for day-
to-day use.
