During a study of the crystallization of the drug ibuprofen from ethanolic solutions, it was necessary to measure crystal size distributions. Ibuprofen is hydrophobic and shows a marked tendency to aggregate in contact with water, a possible suspending liquid. Further the ibuprofen crystals are plate shaped and are easily broken. A surfactant can be used to “wet” the ibuprofen crystals and reduce aggregation. With the liquid cell in the Malvern® laser light scattering sizer, there is agitation and ultrasound can be used. This paper describes experimental results to determine the extent of de-aggregation and breakage of crystals by agitation and ultrasound in the sizing. Ultrasound gives very rapid breakage of the crystals while the agitation gives only minor breakage.
Key words: Ibuprofen, Crystal size distribution, Hydrophobic, Plate shaped.