Size Analysis of Small Particles in Wet Dispersions by Laser Diffractometry: A Guidance to Quality Data

In the present work, the question how to obtain high-quality laser diffraction (LD) results is discussed by investigating various hurdles that can be encountered during particle size measurements in wet dispersions and the associated data interpretation. Following this an effective troubleshooting is discussed based on theoretical insight into the LD measurement. As an important element in the Mie theory, the refractive indices of the model compounds, bedaquiline and cinnarizine, were quantified using the LD software, the Becke line technique, and the single solvent technique, as described by Saveyn et al. [Saveyn H, et al. Part Part Syst Char. 2001;19:426-432]. The influence of parameters such as obscuration level, background quality, and fitting of data were investigated and a summative flow chart has been provided. Through this analysis the present work emphasizes the need for a systematic approach when conducting LD measurements, including standard performance of an obscuration titration and an extended method optimization, to reach high-quality LD results.