shape, and polymorphic form are the critical attributes of
crystalline particles and represent the major focus of today’s
crystallization process design. This work demonstrates how crystal
properties can be tuned efficiently in solution via a tubular crystallizer
that facilitates rapid temperature cycling. Controlled crystal growth,
dissolution, and secondary nucleation allow a precise control of the
crystal size and shape distribution, as well as polymorphic composition.
Tubular crystallizers utilizing segmented flow such as the one presented
in our work can provide plug flow characteristics, fast heating and
cooling, allowing for rapid changes of the supersaturation. This makes
them superior for crystal engineering over common crystallizers. Characterization
of particle transport, however, revealed that careful selection of
process parameters, such as tubing diameter, flow rates, solvents,
etc., is crucial to achieve the full benefits of such reactors.
Abstract. Blending of powders is a crucial step in the production of pharmaceutical solid dosage forms. The active pharmaceutical ingredient (API) is often a powder that is blended with other powders (excipients) in order to produce tablets. The blending efficiency is influenced by several external factors, such as the desired degree of homogeneity and the required blending time, which mainly depend on the properties of the blended materials and on the geometry of the blender. This experimental study investigates the mixing behavior of acetyl salicylic acid as an API and α-lactose monohydrate as an excipient for different filling orders and filling levels in a blender. A multiple near-infrared probe setup on a laboratoryscale blender is used to observe the powder composition quasi-simultaneously and in-line in up to six different positions of the blender. Partial least squares regression modeling was used for a quantitative analysis of the powder compositions in the different measurement positions. The end point for the investigated mixtures and measurement positions was determined via moving block standard deviation. Observing blending in different positions helped to detect good and poor mixing positions inside the blender that are affected by convective and diffusive mixing.
Many active pharmaceutical ingredients (APIs) are small organic molecules that have different polymorphic forms (1). It is well known that the API's polymorphic form can affect its physico-chemical properties, such as density, melting point, solubility, stability, morphology and bioavailability (2). Thus, polymorphic screening is a critical part of preformulation studies. The search for possible polymorphic forms typically begins with crystallization of a drug substance from various solvents, including those frequently used during the final crystallization steps (3, 4). Since the API's physicochemical properties can have a dramatic impact on its therapeutic effect, it is crucial to detect the polymorphic form with the characteristics appropriate for the intended use. For this purpose, the parameters affecting the crystallization process should be controlled and optimized (5). Major limitations to improving the control of crystallization parameters Crystallization of the drug entacapone from binary solvent mixtures was monitored in situ using a Raman optical probe. The recorded Raman spectra and statistical analysis, which included the principal components method and indirect hard modeling made it possible to estimate the starting point of crystallization, to assess crystallization temperatures and to provide information on the polymorphic content of the mixture. It was established that crystallization temperatures were proportional to the volume content of the solvent in mixtures. The samples were also evaluated off-line via Raman spectroscopy and SWAXS. The collected data showed the presence of forms b and g in all solvent mixtures. In a toluene/methanol 30:70 mixture, in addition to forms b and g, at least one of the forms A, D or a was also indicated by SWAXS. The results have shown that the presence of a particular polymorph is strongly dependent on the nature and portion of the solvent in the binary solvent mixture.
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