1. Izon Science Support Centre
  2. qNano
  3. Troubleshooting: TRPS Measurements

How do I increase the particle rate?

Particle rate depends on the concentration of the prepared sample (or calibration) particles as well as the applied pressure. 

We recommend for the particle rate to be between 200-1500 particles/min. 

If the rate is higher than the value above, the likelihood of coincidence events to occur is higher. A coincidence event is when more than one particle passes through the sensing zone at once. If the particle rate is higher than recommended, the software will overestimate the calculation for mean size and underestimate the calculation for particle concentration. 


To increase the rate:

Cause Solution
Sample is too dilute
  1. Ensure a calibrated pipette is used when preparing samples. Pipettes should be calibrated on a regular basis.
  2. Ensure good pipetting technique is used.
  3. Mix the concentrated particles before diluting them in the electrolyte. For biological samples, mix with a pipette or by gently inverting/swirling the samples by hand; vortexing or sonicating can damage biological particles. Non-biological samples can be vortexed, and/or sonicated if required.
  4. Decrease the dilution to obtain a more concentrated sample.
VPM is not applying pressure correctly

Ensure the pressure has been applied correctly. To reapply pressure mid-measurement:

  1. Set the system to "Vent"
  2. Pull the gauge to the "0" position
  3. Disconnect the VPM nozzle from the upper fluid cell
  4. Mix the content of the upper fluid cell using a pipette
  5. Reconnect the VPM nozzle
  6. Set the system to "Seal"
  7. Apply the appropriate pressure


  • Check the high-pressure stage is being used (top knob is pushed down)
  • Inspect and replace the nozzle o-ring if it appears worn
Contact Izon support if the problem persists.