An impinging jet system placed within a stirred-tank reactor was utilized in this work to precipitate an active pharmaceutical ingredient (API), namely griseofulvin, using a solvent/anti-solvent approach. The API was dissolved in an acetone solution. The anti-solvent solution was water added with a polymer (HPMC) and a surfactant (SDS) combination in order to enhance particle stability.

The impinging jet mixer consisted of two jet nozzles arranged diametrically opposed to each other with the outlet tips of the nozzles directed to face each other. The jet nozzles were organized in a submerged arrangement within the stirred-tank reactor. Ultrasonics were also introduced at the point of impingement by way of a sonication probe. The effect of sonication power and angle of impingement of the two jets on the resulting particle size distribution and crystal structure was observed. The particle size distribution was measured for each experiment using a laser diffraction particle size analyzer. The precipitated griseofulvin crystals were also analyzed using Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD) to obtain an image of the crystal shape and structure.

The impinging jets system produced crystals with smaller mean particle sizes when the two jets were oriented 180 degrees apart and pointed directly at each other. The introduction of ultrasonic power at the impingement point resulted in markedly smaller mean particle size and a tighter particle size distribution. In general, the results were highly reproducible. X-Ray diffraction results showed that the crystal structure was unaffected by different operating conditions.