Evaluation of the TSI aerosol impactor 3306/3321 system using a redesigned impactor stage with solution and suspension metered-dose inhalers

Julie A. Harris, Stephen W. Stein, Paul B. Myrdal

Research output: Contribution to journalArticle

5 Scopus citations


The purpose of this research was to evaluate a redesigned impactor stage for the TSI Model 3306 Impactor Inlet with nozzles adjusted to obtain a target cut-point of 4.7 μm. It has been determined that the previous cut-point used in the Model 3306 was nominally closer to 4.14 μm, thus potentially impacting the characterization of aerosol mass. The reassessment of the Model 3306 was performed on 4 solution and 2 suspension metered-dose inhaler (MDI) formulations. The redesigned impactor stage resulted in a 5% to 6% increase in aerosol mass when compared with the previous impactor stage for the products Ventolin-HFA, Proventil-HFA, and 2 cyclosporin solution formulations with high ethanol concentrations (15% wt/wt). For the formulations with low ethanol concentrations (3% wt/wt), minimal differences were observed between the 2 cut-points. In addition, this study reevaluated the requirement of a vertical inlet extension length when using the TSI 3306/3321 system with the redesigned cut-point. It was shown that the use of a 20-cm extension provides mass and aerosol size distributions that are comparable to the Andersen 8-stage Cascade Impactor, for both solution and suspension MDIs. This work indicates that the TSI 3306/3321 system is suitable for preformulation studies of both suspension and solution MDI systems.

Original languageEnglish (US)
Article number20
Pages (from-to)E1-E8
JournalAAPS PharmSciTech
Issue number1
StatePublished - Mar 10 2006



  • Aerosols
  • Metered-dose inhalers
  • Particle sizer
  • Size distribution

ASJC Scopus subject areas

  • Pharmaceutical Science

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