In situ determination of metastable zone width using dielectric constant measurement

Abstract

This study demonstrates the first use of a dielectric constant meter, coupled with an automated data logging module, for in situ monitoring of solution crystallization processes. The results show that this in situ measurement could detect not only the cloud point that corresponds to the onset of nucleation but also the clear point that closely represents the solubility limit. The metastable zone width (MZW) can subsequently be estimated as the gap between the loci of the cloud and clear points. In addition, the general phenomena of the crystallization process could be observed from several different regions of the dielectric constant profile. Direct comparison with turbidity measurement and focused beam reflectance measurement (FBRM) confirms that the cloud and clear points determined by the present dielectric constant measurement are reliable. This study opens new opportunities for the use of the dielectric constant meter as a simple, inexpensive, and convenient alternative tool in the field of crystallization process monitoring. © 2010 American Chemical Society.