Low A260/230 Ratio Indicates Contaminant Carryover

Symptom

Spectrophotometric analysis shows A260/230 ratio below 1.8-2.0, indicating residual guanidine salt or other chaotropic agent contamination in the purified RNA.

1. 1 Wash steps incomplete or skipped entirely before elution
2. 2 Column tip contacted flow-through during wash steps, re-introducing contaminants
3. 3 Insufficient centrifugation after wash steps - residual wash buffer remains on column
4. 4 Collection tube reused without removing residual wash buffer from tube rim

1. 1 Perform all wash steps as specified in protocol; do not skip or reduce number of washes
2. 2 During wash and elution steps, carefully avoid contact between column tip and flow-through; if contact occurs, repeat centrifugation for 1 minute
3. 3 After final wash, centrifuge column for full recommended time to remove all traces of wash buffer
4. 4 When reusing collection tubes, blot the rim of the tube on a Kimwipe before reattaching to column
5. 5 If A260/230 remains low, perform an additional wash step or repeat the entire cleanup procedure

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