Real-time image-based investigation of spheronization and drying phenomena using different pellet formulations

Extrusion-spheronization (ES) is a frequently used agglomeration process in the pharmaceutical industry to manufacture spherical solid units or pellets with a narrow size and shape distribution. In this study, photometric stereo imaging was applied in real-time during the final steps of the ES process, being spheronization and drying. In addition to the pellet size distribution of undispersed (wet) samples, the imaging technique captures visual information on pellet shape and surface brightness. Pellet samples were taken at 20 time points during spheronization and were imaged at-line (during spheronization) and off-line (after spheronization). Particle size distributions and visual image information were both used to characterise the spheronization behaviour of different formulations. Next, particle size distributions and surface brightness values calculated from the at-line obtained images during fluid bed drying of pellets were analysed. The particle size distribution and brightness value changes occurring during pellet drying were explained both by the reduction in residual moisture content and drug solid-state transition. Due to the rapidness of the technique with regard to sample preparation, sample measurement and the acquisition of results in combination with the possibility to measure undispersed (wet) samples, valuable information on spheronization and drying characteristics of different formulations was obtained in real-time.

Near infrared and Raman spectroscopy for the in-process monitoring of pharmaceutical production processes

Within the Process Analytical Technology (PAT) framework, it is of utmost importance to obtain critical process and formulation information during pharmaceutical processing. Process analyzers are the essential PAT tools for real-time process monitoring and control as they supply the data from which relevant process and product information and conclusions are to be extracted. Since the last decade, near infrared (NIR) and Raman spectroscopy have been increasingly used for real-time measurements of critical process and product attributes, as these techniques allow rapid and nondestructive measurements without sample preparations. Furthermore, both techniques provide chemical and physical information leading to increased process understanding. Probes coupled to the spectrometers by fiber optic cables can be implemented directly into the process streams allowing continuous in-process measurements. This paper aims at reviewing the use of Raman and NIR spectroscopy in the PAT setting, i.e., during processing, with special emphasis in pharmaceutics and dosage forms.

Raman spectroscopy as a process analytical technology (PAT) tool for the in-line monitoring and understanding of a powder blending process

The aim of this study is to propose a strategy to implement a PAT system in the blending step of pharmaceutical production processes. It was examined whether Raman spectroscopy can be used as PAT tool for the in-line and real-time endpoint monitoring and understanding of a powder blending process. A screening design was used to identify and understand the significant effects of two process variables (blending speed and loading of the blender) and of a formulation variable (concentration of active pharmaceutical ingredient (API): diltiazem hydrochloride) upon the required blending time (response variable). Interactions between the variables were investigated as well. A Soft Independent Modelling of Class Analogy (SIMCA) model was developed to determine the homogeneity of the blends in-line and real-time using Raman spectroscopy in combination with a fiber optical immersion probe. One blending experiment was monitored using Raman and NIR spectroscopy simultaneously. This was done to verify whether two independent monitoring tools can confirm each other's endpoint conclusions. The analysis of the experimental design results showed that the measured endpoints were excessively rounded due to the large measurement intervals relative to the first blending times. This resulted in effects and critical effects which cannot be interpreted properly. To be able to study the effects properly, the ratio between the blending times and the measurement intervals should be sufficiently high. In this study, it anyway was demonstrated that Raman spectroscopy is a suitable PAT tool for the endpoint control of a powder blending process. Raman spectroscopy not only allowed in-line and real-time monitoring of the blend homogeneity, but also helped to understand the process better in combination with experimental design. Furthermore, the correctness of the Raman endpoint conclusions was demonstrated for one process by using a second independent endpoint monitoring tool (NIR spectroscopy). Hence, the use of two independent techniques for the control of one response variable not only means a mutual confirmation of both methods, but also provides a higher certainty in the determined endpoint.