Magnetic Bead Contamination in Final cfDNA Eluate

Symptom

Visible brown particles or turbidity in the final DNA eluate. This may cause downstream assay interference, optical measurement errors, or sequencing library preparation issues.

1. 1 Magnetic separation time less than 2 minutes before transferring final elution
2. 2 Insufficient magnetic field strength allowing beads to remain suspended
3. 3 Pipette tip disturbing the bead pellet during final elution transfer
4. 4 Tubes removed from magnetic rack prematurely during elution collection

1. 1 Leave tubes on magnet for minimum 2 minutes before collecting final elution
2. 2 Ensure supernatant is completely clear before pipetting the eluate
3. 3 Carefully transfer elution without disturbing the bead pellet; pipette slowly
4. 4 Leave the final 1-2 µL of eluate in the tube to avoid aspirating beads
5. 5 If beads are transferred, briefly spin and re-magnetize the eluate tube, then transfer to a fresh tube

Related Video (1)

Thermo Fisher Scientific ★ 92

How to Isolate Cell-Free DNA from Plasma | cfDNA Purification

"Directly demonstrates manual cfDNA isolation workflow including magnetic bead separation steps where timing is critical to prevent contamination in final eluate"