Mechanistic Modelling and Mechanistic Monitoring: Simulation and Shadowgraph Imaging of Particulate Dissolution in the Flow-Through Apparatus

Characterization and Simulation of Hydrodynamics in the Paddle, Basket and Flow-Through Dissolution Testing Apparatuses - A Review

“…Shadowgraph imaging is a noninvasive optical technique which, in addition to quantifying the size and shape of particles at a point in time, can also quantify their absolute velocity ( Figure 1) (4,14). Digital images of particle-laden fluid are captured against a background of pulsed light.…”

“…In terms of particulate systems in the FTC apparatus, shadowgraph imaging has demonstrated that suspended particles do follow a somewhat pulsing motion, however, the motion of the particles can be complex (4). In a hypothetical situation, a change in flow rate should not impact the relative fluid velocity, however, the effect of flow rate on dispersion of the powder bed and particle interactions with the cell surfaces will be affected by flow rate.…”

“…In a hypothetical situation, a change in flow rate should not impact the relative fluid velocity, however, the effect of flow rate on dispersion of the powder bed and particle interactions with the cell surfaces will be affected by flow rate. Shadowgraph imaging has proven useful for exploring particle behavior within the FTC apparatus in terms of particle velocities, sizes, and particle agglomeration tendencies (4,14).…”

“…However, in general, agitation rate is expected to have a less significant effect on dissolution of a highly soluble drug, which might dissolve rapidly even in low agitation conditions, compared to a more poorly soluble drug. If a dosage form consists of, or disintegrates into, flocculent particulates, these may move with the moving fluid and, therefore, the relative fluid velocity that the dosage form is exposed to is the velocity factor relevant for drug dissolution (4). In such a situation, agitation of the dissolution medium would be relevant to overall mixing to enable generation and retention of uniform concentration within the apparatus for reliable sampling and also for sink conditions local to the dissolving surface, if applicable.…”

Modelling and shadowgraph imaging of cocrystal dissolution and assessment of in vitro antimicrobial activity for sulfadimidine/4-aminosalicylic acid cocrystals

“…One of the advantages is that no probe is required; instead an external source and a recording plane (i.e. a camera), onto which the shadow of the varying density field is projected, are necessary (D'Arcy D and Persoons, 2011). A shadow is generated because a laser ray is refractively deflected so that the position on the recording plane where the undeflected ray would arrive remains dark and at the same time the position where the deflected ray arrives appears brighter.…”