1. Collect used Qiagen collection tubes and columns in a 50 ml tube, fill with 1M HCl. Allow them to sit for at least 24 hours but not more than a month. For Tip20 or Tip100 columns, immerse in 1M HCl in 50 ml tubes for a week.

2. The following day (or after a week for Tip20 or Tip100), transfer the columns and the tubes in a different plastic container (empty tip box is fine) and save 1M HCl in 50ml tube for subsequent columns. The same HCl solution can be reused for up to one month. Ensure you replace it with fresh 1M HCl monthly.

3. Rinse the columns and tubes in the container, once with distilled water (swirl to mix and then empty the container).

4. Reassemble the collection tube and column. Place the Miniprep columns in a tube rack. For Tip20 or larger, use the Qiagen rack if available.

5. Fill the columns with distilled water. Centrifuge the Miniprep columns for 30 seconds at maximum speed, or allow the water to flow through by gravity for Tip20 or Tip100. Discard the water from the collection tube. Repeat this washing step once more.

6. Load the Miniprep columns with 200 μl of QBT buffer for equilibration (use 1-4 ml for Tip20 or Tip100). Spin for 1 minute or allow it to gravity flow for Tip20 or larger. If you lack Qiagen's QBT buffer, a homemade version can be made with 750 mM NaCl, 50 mM MOPS (pH 7.0), 15% isopropanol, and 0.15% Triton X-100.

7. Decant the QBT buffer and empty the collection tubes with the pipette tip.

8. Erase any markings or labels from the columns and tubes with ethanol.

9. Draw a line with ethanol resistance marker on the column to indicate the number of times the column has been regenerated.

10. Place the Miniprep columns with their collection tubes into washed and cleaned 50 ml tubes.

11. Close the tube lids and store them in a kit or in the communal area for further reuse. Proceed to use the column as if it were new from a kit.

Note: These regenerated columns can be reused up to 20 times without a significant decline in the quality or yield of extracted plasmid DNA.