Particle formation

Abstract

Method for preparing a target substance in particulate form, comprising introducing into a particle formation vessel, through separate first and second fluid inlets respectively, (a) a “target solution/suspension” of the substance in a fluid vehicle and (b) a compressed fluid anti-solvent, and allowing the anti-solvent to extract the vehicle so as to form particles of the substance, wherein the anti-solvent fluid has a sonic, near-sonic or supersonic velocity as it enters the vessel, and wherein the anti-solvent and the target solution/suspension enter the vessel at different locations and meet downstream (in the direction of anti-solvent flow) of the second fluid inlet. Also provided is apparatus for use in such a method.

1 . An apparatus for preparing a target substance in particulate form, comprising: 
 (i) a particle formation vessel;    (ii) a first fluid inlet for introducing into the vessel a solution or suspension of the target substance in a fluid vehicle; and    (iii) a second fluid inlet, separate from the first, for introducing a compressed anti-solvent fluid into the particle formation vessel, wherein the first and second fluid inlets are so arranged that, in use, a target solution/suspension introduced through the first inlet and an anti-solvent introduced through the second inlet enter the particle formation vessel at different locations and meet immediately downstream in the direction of anti-solvent flow of the second fluid inlet.    
   
   
       2 . The apparatus of  claim 1 , wherein the second fluid inlet provides a restriction at the point of anti-solvent fluid entry into the particle formation vessel.  
   
   
       3 . The apparatus of  claim 1 , wherein the second fluid inlet comprises a nozzle having at least two coaxial fluid passages.  
   
   
       5 . The apparatus of  claim 1 , wherein the outlet of the first fluid inlet into the particle formation vessel is immediately downstream, in the direction of anti-solvent flow in use, of that of the second fluid inlet.  
   
   
       5 . The apparatus of  claim 1 , wherein the outlet of the first fluid inlet is downstream, in the direction of anti-solvent flow in use, of that of the second fluid inlet, and wherein the separation between the two outlets is from 10 to 40 times the diameter of the outlet of the second fluid inlet.  
   
   
       6 . The apparatus of  claim 1 , wherein the outlet of the first fluid inlet is positioned such that, in use, it is within the flow of anti-solvent fluid exiting the second fluid inlet.  
   
   
       7 . The apparatus of  claim 1 , wherein the outlet of the first fluid inlet has a smaller cross sectional area than that of the second fluid inlet.  
   
   
       8 . The apparatus of  claim 1 , wherein the center of the outlet of the first fluid inlet is positioned in line with the central longitudinal axis of the second fluid inlet.  
   
   
       9 . The apparatus of  claim 1 , wherein the first and second fluid inlets are arranged so that at the point where the target solution/suspension and the anti-solvent meet, the angle between their axes of flow is from 70° to 110°.  
   
   
       10 . The apparatus of  claim 9 , wherein the first and second fluid inlets are arranged so that at the point where the target solution/suspension and the anti-solvent meet, their respective axes of flow are approximately perpendicular.  
   
   
       11 . The apparatus of  claim 1 , additionally comprising a source of a compressed fluid and optionally, a source of a target solution or suspension.  
   
   
       12 . The apparatus of  claim 1 , further comprising a pressure controller in the particle formation vessel.  
   
   
       13 . The apparatus of  claim 1 , wherein the particle formation vessel contains particle collection means.  
   
   
       14 . The apparatus of  claim 1 , wherein the first and second fluid inlets are provided as part of a single fluid inlet assembly which may be placed in fluid communication with the particle formation vessel and with sources of the anti-solvent fluid and the target solution/suspension.