BD FACSCanto II, Справочное руководство, Страница: 108 / 158

108 BD FACSCanto II Flow Cytometer Reference Manual
Tube to Flow Cell
When you place a tube on the cytometer, sample travels up the sample injection
tube (SIT) in a separate, pressurized stream. It arrives in the lower chamber of the
flow cell at a slightly higher pressure relative to the sheath fluid. The conical
shape of the lower chamber creates a hydrodynamic focusing that carries the
sample particles in a stable stream upward through the center of the flow cell. In
the flow cell, laser beams interrogate the sample, one particle at a time.
(Figure A-2).
The difference in pressure between the sample stream and sheath fluid stream can
be used to vary the diameter of the sample stream, also known as the sample
core. Increasing the sample pressure increases the core diameter and therefore the
flow rate (Figure A-2).
• A higher flow rate is generally used for measurements such as
immunophenotyping. The data is less resolved but is acquired more
quickly.
• A lower flow rate is generally used in applications where greater resolution
is critical.
Figure A-2 Hydrodynamic focusing of the sample core through the flow cell
When using BD FACSCanto clinical software, the cytometer automatically
regulates the sample pressure according to the currently selected panel.
high sample
pressure
(120 µL/min)
low sample
pressure
(10 µL/min)
red beam
sheath fluid
blue beam
sample
sheath fluid sheath fluid
sample
sheath fluid
violet beam