Simple and reliable quartz crystal microbalance technique for determination of solubility by cooling and heating solution.

A quartz crystal microbalance (QCM) is presented as a promising technique for determining the solubility and induction of nucleation via the cooling and reverse heating of a solution. When cooling and heating a solution, the resonant frequency (F) and resonant resistance (R) of the QCM responses change significantly due to vibrational loss related to the viscous and elastic friction that depend on the solution viscosity and solid mass on the sensor, respectively. Thus, obvious refraction points appear in the QCM response profile at the induction point of primary nucleation during cooling crystallization and at the saturated point during heating dissolution. Using an F-R plot of the QCM responses, the phase changes between liquid and solid at the induction and saturated points are confirmed. When compared with focused beam reflectance measurement (FBRM) and gravimetric methods, the QCM method is confirmed to be highly accurate and reliable for determining the solubility, making it a highly promising method for determining solubility and crystal nucleation with minimal effort based on simple temperature cycling, thereby avoiding precalibration and sampling.