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AAPS PharmSciTech. 2016 April; 17(2): 380–388.
Published online 2015 July 14. doi:  10.1208/s12249-015-0346-5
PMCID: PMC4984894

Effects of Temperature and Humidity on Laser Diffraction Measurements to Jet Nebulizer and Comparison with NGI

Abstract

Laser diffraction (LD) and next generation impactor (NGI) are commonly used for the evaluation of inhaled drug formulations. In this study, the effect of temperature and humidity on the assessment of the nebulizer particle size distribution (PSD) by LD was investigated, and the consistency between NGI and LD measurements was evaluated. There was an increase in particle size with higher temperature or lower humidity. The particle population with a diameter less than 1 μm was significant at a temperature of 5°C or at relative humidity >90%; however, the same particle population became undetectable when temperature increased to 39°C or at relative humidity of 30–45%. The results of the NGI and LD measurements of aerosol generated from three types of jet nebulizers were compared. A poor correlation between the NGI and LD measurements was observed for PARI LC (2.2 μm) (R2 = 0.893) and PARI LC (2.9 μm) (R2 = 0.878), while a relatively good correlation (R2 = 0.977) was observed for the largest particle size nebulizer (PARI TIA (8.6 μm)). We conclude that the ambient environment and the nebulizer have significant impacts on the performance and consistency between these instruments. These factors should be controlled in the evaluation of inhaled aerosol drug formulations when these instruments are used individually or in combination.

KEY WORDS: impactor, jet nebulizer, laser diffraction, particle size distribution

Articles from AAPS PharmSciTech are provided here courtesy of American Association of Pharmaceutical Scientists