How do I prepare the calibration particles?

Izon Science calibration particles (carboxylated polystyrene) contain:

  • Carboxylated polystyrene particles (size and concentration certified by Izon)
  • Deionised water
  • 0.05% w/v Sodium azide to prevent microbial growth


Calibration particles may settle or form loose aggregates during transit and storage. For accurate measurements the concentrated particle stock must be homogeneously dispersed throughout the carrier fluid and any aggregates broken up. Where possible, the calibration particles must be suspended in the same solution that the samples are suspended in. 

Particles with diameters in the 10+ μm range settle out of solution very rapidly. It is therefore vital that the samples are vortexed immediately prior to all measurements.


To dilute the calibration (or sample) in electrolyte:

  1. Vortex the concentrated particle stock in short bursts for 30 seconds at medium speed. For larger particles (>500 nm) a few seconds vortex mix is recommended prior to dilution to re-suspend any settled particles.
  2. Pipette 1 mL (1000 μL) of electrolyte into a small clean vial.
  3. Pipette calculated volume of undiluted particles into the electrolyte.
  4. Place the lid on the vial and vortex at medium speed.
  5. Label the vial correctly with the sample name and dilution factor


  • For most calibration particles, a 1:1000 dilution is suitable.
  • If the calibration particle rate is too low, make a more concentrated solution e.g. 1:500 dilution. 
  • Neutral calibration particles are available upon request. This is relevant for any zeta potential work or for measurements using a negative voltage. Please contact Izon Support to place your order.