SCYM Instrument Operation 5

Question 1

A technologist is troubleshooting a flow cytometer and finds that all fluorescence channels show elevated background, but scatter parameters are normal. The most likely cause is:

Accepted Answer

Ambient light entering the optical system or a contaminated flow cell

Answer

Elevated background across all fluorescence channels with normal scatter typically points to stray light contamination, either from ambient light or a fluorescent residue in the flow cell.

Question 2

In a high-speed cell sorter operating with a vibrating nozzle, the droplet break-off frequency is determined by:

Accepted Answer

The piezoelectric crystal oscillation frequency applied to the nozzle

Answer

The piezoelectric crystal in the sort head vibrates at a defined frequency, creating regular droplet break-off from the stream.

Question 3

Which of the following is NOT a standard daily instrument performance check for a flow cytometer?

Accepted Answer

Recalibrating the electrostatic deflection plates

Answer

Recalibrating deflection plates is not a routine daily check; it is an instrument-specific maintenance task performed less frequently or during troubleshooting.

Question 4

When using an acoustic focusing cytometer (e.g., Attune), how is cell focusing achieved differently from conventional hydrodynamic focusing?

Accepted Answer

Acoustic waves push cells to the center of the channel, reducing or eliminating sheath fluid requirements

Answer

Acoustic focusing cytometers use ultrasonic standing waves to position cells in the center of the microchannel, enabling faster sample rates with less sheath fluid.

Question 5

Which instrument setting is most critical to adjust when switching from immunophenotyping peripheral blood to analyzing small particles such as platelets or extracellular vesicles?

Accepted Answer

Trigger threshold lowered and scatter voltages optimized for small particles

Answer

Small particles like platelets and extracellular vesicles require a lower trigger threshold and optimized scatter voltages to be detectable above instrument noise.

(SCYM) Specialist in Cytometry Practice Test

(SCYM) Specialist in Cytometry Practice Test

SCYM Instrument Operation 5