1. Select a centricon with molecular weight cut-off one-half to one third of the protein's molecular weight.

2. Attach a filtrate vial to the sample reservoir.

3. Add samples to the sample reservoir.

4. Centrifuge at an appropriate speed for an appropriate time.

5. For desalting or changing buffer, dilute the sample, then repeat step 4 until desired result has been achieved.

6. To recover concentrated protein, remove filtrate vial, place a retentate vial on sample reservoir. Invert the assemble and centrifuge briefly.

7. Remove the retentate vial, cap, and store.