Browsing by Subject "Surface characterization"

During co-processing, magnesium stearate can induce surface coating on carrier particles in powders which contain at least one other component in addition to magnesium stearate. Magnesium stearate is sometimes added to powder mixtures as it is known to have beneficial effects on powder characteristics, such as physical and chemical stability, and flowability. In order to fully optimize and control the coating/mixing process, it is necessary to be able to characterize the quality of surface coating. Various methods can be used in determining the coating of powder particles. They can roughly be divided into two different categories: direct and indirect methods. For example, spectrophotometric instruments, which are used to visually express the element distribution on particle surface, are considered direct methods. Indirect methods include methods in which coating parameters are inferred using other properties such as water sorption and powder flowability. Principally direct methods have been used in previous studies to determine the quality of coating. Therefore, the area of interest was especially to study indirect methods and compare them to results obtained using direct methods. Having knowledge of the suitability of indirect methods would be interesting as they might have many benefits compared to direct methods, such as quicker analysis speed and cost-efficiency. The aim of the study was to examine the suitability of direct and indirect methods in studying the surface of powders containing magnesium stearate and active pharmaceutical ingredients (APIs) or lactose, more closely how magnesium stearate was placed on carrier particles as well as the uniformity and the thickness of coating layer. The used methods were selected using literature and own consideration while taking the available equipment into account. The powders containing API (d50 < 10 μm) or lactose (d50 > 80 μm) with magnesium stearate had substantially differing characteristics and thus behaved differently. Therefore, there were differences in the suitability of analytical methods in determining surface of powders. Powders containing lactose and magnesium stearate were able to be examined using direct methods (SEM-EDS and ToF-SIMS) and several indirect methods. Samples with API and magnesium stearate were able to be studied with fewer methods. Validation of the suitability of these methods need more research. However, according to the results from this study, it is probable that surface characterization of studied co-particles can be achieved with direct, but also with indirect methods.