Determination of Particle Size and Microstructure in Topical Pharmaceuticals

Abstract

This chapter focuses on techniques for determining API particle size in topical semisolid products using manual microscopy, automated microscopy, morphologically directed Raman spectroscopy, dynamic light scattering, and laser diffraction. The use of optical microscopy, both bright field and polarized light, for the determination of formulation microstructure is also discussed. For topical emulsions, this includes characterizing globule size and being able to identify polarized light microscopy birefringence patterns typical of liquid crystal stabilized emulsions. Emphasis is placed on sample preparation techniques that have been found successful in characterizing particle or globule sizes accurately without biasing the results.