Application of the turbidity measurements to study in situ crystallization of calcium phosphates

Crystallisation of phosphates revisited: a multi-step formation process for SrHPO4

SrHPO4 is used in a multitude of applications, including biomedicine, catalysts, luminescent materials, and batteries. However, the performance of these materials depends on the ability to control the formation and transformation of strontium phosphates. This work focuses on the application of in situ and ex situ measurements, including synchrotron-based X-ray diffraction (XRD) analysis, luminescence of Ce3+ and Eu3+ dopants, light transmission, reflectance, and thermogravimetry to track structural changes in SrHPO4 under different experimental conditions. Ex situ analysis of aliquots revealed favourable crystallisation of β-SrHPO4 through the formation of Sr6H3(PO4)5·2H2O as an intermediate. Furthermore, in situ analysis showed that the reaction mechanism evolves via the initial formation of amorphous strontium phosphate and Sr5(PO4)3OH, which subsequently transforms to γ-SrHPO4. Analysis of the luminescence properties of the lanthanide dopants provided insights into the coordination environments of the substituted Sr2+ sites.

In situ luminescence analysis: a new light on monitoring calcium phosphate phase transitions

In situ luminescence measurements allow monitoring the phase transitions of biologically relevant calcium phosphates with high sensitivity, independent of synchrotron radiation.

In-line non-invasive turbidimetry as a tool to ensure content uniformity in the betamethasone filling process

The filling process of liquid suspensions is a difficult operation,mainly due to drug settling. Small variations during the process may lead to serious deviations in the API content uniformity of the finished product, particularly if the drug settles fast. Real-time non-invasive monitoring of liquid suspensions is a useful approach to ensure an acceptable API content in the finished product. The aim of this study was to develop a method based on non-invasive turbidity measurements for in-line determinations of betamethasone content uniformity during the filling process of injections. Owing to the constructive features of the developed system, the determinations were performed in a non-destructive and non-invasive way, thus allowing the analysis of the whole batch and minimizing the risk of contaminating the product. The results obtained by the method proposed in this study demonstrated that non-invasive turbidimetry is a powerful tool for continuous monitoring of the filling process of betamethasone injections, within the Quality by Design framework (FDA, 2009).