Integrated automated filtration for separation, washing and drying of peptide crystals

An integrated process of crystal separation, washing and drying of insulin or insulin analogues, comprising the steps of:

• a) preparing a crystal suspension of insulin or insulin analogue using Zn Cl2 and adjusting the pH of the crystal suspension to between 4.5 and 8.5;
• b) pouring the crystal suspension obtained from step a) onto a filter fabric placed on an area ranging between 80 cm2 to 100 cm2 of a pressure filtration unit;
• c) purging the pressure filtration unit with nitrogen gas via an inlet port of the pressure filtration unit to obtain a filter cake;
• d) collecting a filtrate via outlet port of the pressure filtration unit;
• e) pouring 100% acetonitrile, butanol, ethanol, ethyl acetate or isopropanol as a solvent wash on the filtrate and purging nitrogen gas via an inlet port of the pressure filtration unit at a pressure of 1 to 2.5 bar;
• f) collecting the filtrate via an outlet port of the pressure filtration unit;
• g) repeating steps e) and f) to provide further solvent washes on the filtrate and thereby providing a filter cake;
• h) drying the filter cake by passing nitrogen gas through the filter cake at a pressure range of 1 bar to 2.5 bar;
• and
• i) removing the filter cake in the form of a dried powder, wherein the process is conducted as a single continuous process.