# Filter-centrifuge your sample with Vivaspin® 20
This how-to guide shows you how to concentrate your sample with the [filter-centrifuge method](/protocols/prepare-your-sample/hit-the-right-concentration/concentrate-your-sample/filter-centrifuge-your-sample.md) using a [Vivaspin® 20](https://shop.sartorius.com/dk/p/vivaspin-20-centrifugal-concentrator-polyethersulfone-12-pc/VS2061). Follow the steps below.
{% stepper %}
{% step %}
### Rinse filter
Rinse to remove trace biocides and glycerine present on the filters:
1. Add 20 mL of sterile-filtered diluent to the concentrator (see 4 in the figure above) of the Vivaspin® 20.
2. Place Vivaspin® 20 in the centrifuge.
3. Add another 50 mL centrifuge tube on the other side to balance the rotor.
4. Make sure the *mL* scale faces the exterior of the centrifuge. If the tube is not oriented properly, the 50 µL dead stop won’t work optimally.
5. Centrifuge (1000 x*g*, 30 seconds)
6. Discard the liquid in the filtrate container (see 6 in the figure above).
There will be approximately 50–150 µL liquid left in the concentrator due to the dead stop. You may discard this with a pipette but it’s not necessary at this time.
{% endstep %}
{% step %}
### Centrifuge your sample
1. Add 20 mL of your sample in the concentrator (see 4 in the figure above). E.g., pour or pipette to the 20 mL mark. Note down the volume we added here.
2. Make sure that the rotor is balanced
3. Make sure that the *mL* scale on the tubes face the exterior of the centrifuge.
4. Centrifuge (1000 x*g*, 30 seconds)
After centrifugation, around 50 µL of residual volume is left in the concentrator due to the dead stop. If the sample is highly viscous or dirty, it may be necessary to extend the centrifugation time. The volume scale on Vivaspin® helps you to determine if this is necessary.
{% endstep %}
{% step %}
### Recover your sample
1. Add [diluent](/encyclopedia/item-register/vials-flasks-and-liquids/dilution-liquid-5-l.md) to the 5 mL mark of Vivaspin® 20. This ensures enough volume for a BactoBox® measurement later on.
2. Resuspend bacteria:
1. Use a pipette to repeatedly aspirate and rinse the membrane. Usually, 20 repetitions are enough.
2. Gentle vortexing aids complete sample recovery. Vortex propagation from the bottom of the tube won’t work because the liquid is in the upper compartment. Instead, use an adapter (e.g. Vortex Genie and SI—V525) to mount the tubes. Start briefly with a speed setting of 4. Wait for the vortex/cyclone to appear and change to 3 for gentle vortexing for 30 seconds.
3. Pour the resuspended, concentrated sample into an [empty vial](/encyclopedia/item-register/vials-flasks-and-liquids/empty-vial.md).
{% endstep %}
{% step %}
### That is it!
You can now measure you sample vial with BactoBox®.
{% endstep %}
{% endstepper %}
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