16. Pre-filter and reusing old cleaned sterile filters step. The GDX filters have a pre-filter built into them and it is a 10. By cleaning an old filter out with methanol you can use it again as a pre-filter if your solution hasn't cleared enough. A. Draw the coffee filtered solution into the syringe. B. Place a white pre-filter onto the tip of the syringe. C. Push the liquid through into any vial. D. After the solution is all into the and pre-filtered remove the pre-filter. E. Draw more solution into the syringe.