What is System Verification?

System verification is the process of checking that your particle size analyzer is performing correctly. This test consists of using a well-known material to challenge the instrument. If the measured results agree with the material specification, then the analyzer is working correctly. Otherwise some action should be taken to bring the analyzer back into working condition.


When should I Verify my System?

Anyone using a particle size analyzer should verify the performance of the instrument on a regular basis. The frequency of system verification should be a risk based decision. If a company runs their plant based on particle size analysis of the product, then daily verification may be appropriate. A research group that uses their instrument a few times a year may only verify their system once a year. Other customers will fall somewhere in between, and HORIBA recommends that all customers verify performance of their instrument on at least an annual basis.

Other scenarios might also require or recommend a system verification test. Users subject to FDA oversight, or other regulatory bodies, may wish to verify system performance after moving the instrument to a new location or after any physical shock to the tool.


Verification vs. Calibration

Calibration implies challenging an instrument with a known sample and then adjusting the instrument to achieve the desired result. Verification involves challenging the instrument with a known sample to confirm that the expected result is generated. If the system does not meet the pass/fail verification criteria then the instrument has a fault which must be corrected and then the system is tested again to determine if the fault has been fixed.

Laser diffraction analyzers and dynamic light scattering systems are based on first principles, so they are not calibrated, but rather are subjected to verification tests to assure system performance. A pass/fail criteria should be documented prior to the verification test, a qualified person should test the system, and if the system passes it can then be used in confidence. If the system fails the test the optics are first cleaned and/or adjusted and the system is tested again. If the system still fails, then we recommend calling the HORIBA service team for technical attention.

The HORIBA LA-960 software has automated verification process and calculations features. Click the link below to read the technical note TN169 on automated verification.

TN169 LA-960 Automated Verification Functions


Which Standards should I Use?

A range of particle size standards are available for verification of particle characterization instruments. The information below lists several sources of particle size standards and HORIBA's guidance on choosing appropriate materials.


Monodisperse Latex Standards

Monodispersed materials feature extremely narrow particle size distributions. Polystyrene latex image courtesy of Thermo Scientific.
Click to enlarge: Monodispersed materials feature extremely narrow particle size distributions. Polystyrene latex image courtesy of Thermo Scientific.
  • Thermo Scientific offers the range of particle standards originally known as Duke Scientific. The product line includes size and count standards along with particles with specific properties such as magnetic, fluorescent, dyed, etc. Information can be found on the Thermo Scientific website here.
  • Bangs Laboratories manufactures a wide range of particle standards including monodisperse latex standards and other specialized particle products. Information can be found at the Bangs Laboratories website here.
  • Polysciences categorizes their monodisperse NIST-traceable standards into the ranges of nanobeads, microbeads, and megabeads. Information on these standards can be found at the Polysciences website here.
  • Sigma-Aldrich has particle size standards available through their catalog or website. Information can be found on the Sigma-Aldrich website here.

Polydisperse Glass Standards

Laser diffraction analyzers are often verified using standards with a known distribution of particles. Both ISO13320 and USP<429> suggest using polydisperse standards when verifying laser diffraction analyzers. Polydisperse standards are available through several sources including those listed below.


Laser Diffraction Product Pages

LA-960

The LA-960 uses Mie Scattering (laser diffraction) to measure particle size of suspensions or dry powders. The speed and ease-of-use of this technique makes it the popular choice for most applications.

LA 300

The LA-300 uses Mie Scattering (laser diffraction) to measure particle size of suspensions. The speed and ease-of-use of this technique makes it the most popular for many applications.