Validation of laser diffraction method as a substitute for cascade impaction in the European project for a nebulizer standard

The project for a European standard testing procedure to characterize nebul izers in terms of particle size distribution has been based on using the An dersen-Marple personal cascade impactor model 298 (A-MPCI) with a sodium fl uoride reference solution. In the present study methods based on laser diff raction (Mastersizer-X) and time-of-flight (TOF)(APS (R)) and another casca de impactor (GS1-CI) were compared with the A-MPCI. Two types of nebulizer (Pari LC+(R) and Microneb (R)) were tested with all apparatuses, and a thir d type of nebulizer (NL9 (R)) was tested with the A-MPCI and Mastersizer-X. Nebulizers were charged with a solution of sodium fluoride in conditions r eproducing the European Committee for Normalization (CEN) protocol. There w as no difference between the Mastersizer-X and the A-MPCI or between the GS 1-CI and the A-MPCI in terms of mass median aerodynamic diameter (MMAD). Co mparison between the APS (R) and the A-MPCI showed a significant difference with the Microneb (R). The geometric standard deviations (GSD) obtained wi th the A-MPCI were on average 10% greater than GSD obtained with the other apparatuses, but the differences were not statistically significant. We con clude that laser diffraction can be used for particle size distribution in the context of the European standard, and that the Mastersizer-X is particu larly interesting for industrial practice in view of its simplicity and rob ustness.