Summary

Multi-stage cascade impactors (CIs) are the preferred measurement technique for the assessment of aerodynamic particle size distribution of an inhalable aerosol. Stage mensuration using optical image analysis is the recommended compendial method for monitoring CI “fitness for purpose ” within a GxP environment. The EPAG Impactor Sub-Team has undertaken an inter-laboratory study to assess the accuracy and precision of a range of currently used mensuration systems. Measurement of two Andersen cascade impactor “reference ” stages confirmed that these systems were capable of reproducible jet measurement. In most cases, overall measurement error was found to be around 1 % of nominal jet diameter. Observed small, but consistent differences between ‘dots ’ and ‘spots ’ of a calibrated chromium-plated reticle were attributed to treatment of partially-lit pixels along the circumference