Desalting DNA

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This procedure removes salts, enzymes, and very small DNA fragments from a sample.

1. Add 3 volumes of Buffer QX1 to 1 volume of sample (eg. if sample is 100 uL, add 300 uL of Buffer QX1). <br>
NB. Ensure that solution is yellow in colour. If it is orange or purple, add 10 uL of 3M sodium acetate and mix to return solution to yellow colour. <br>
2. Vortex QIAEX II for 30 sec to resuspend beads. <br>
3. Add 10 uL of QIAEX II to sample for every 5 ug of DNA (eg. if sample contains 15 ug of DNA, add 30 uL of QIAEX II), vortex to mix. <br>
4. Incubate sample at room temperature for 10 min, vortexing every 2 min to resuspend beads. <br>
5. Centrifuge samples for 30 sec and remove supernatant. <br>
6. Add 500 uL of Buffer PE to sample, centrifuge for 30 sec and discard supernatant. <br>
7. Repeat step 6. <br>
8. Allow pellet to air-dry for 10 to 15 minutes until it becomes white. <br>
9. Add 20 uL of H2O to pellet, vortex to resuspend. <br>
10. Incubate at room temperature for 5 min. <br>
11. Centrifuge samples for 30 sec, remove supernatant to clean tube and preserve this supernatant as it contains the desalted DNA.