Low A260/230 Ratio Indicates Contaminant Carryover (RNA Cleanup)

Question

Accepted Answer

Spectrophotometric analysis shows A260/230 ratio below 1.8-2.0, indicating residual guanidine salt or other chaotropic agent contamination in the purified RNA. Common causes: 1) Wash steps incomplete or skipped entirely before elution 2) Column tip contacted flow-through during wash steps, re-introducing contaminants 3) Insufficient centrifugation after wash steps - residual wash buffer remains on column 4) Collection tube reused without removing residual wash buffer from tube rim Solutions: 1) Perform all wash steps as specified in protocol; do not skip or reduce number of washes 2) During wash and elution steps, carefully avoid contact between column tip and flow-through; if contact occurs, repeat centrifugation for 1 minute 3) After final wash, centrifuge column for full recommended time to remove all traces of wash buffer 4) When reusing collection tubes, blot the rim of the tube on a Kimwipe before reattaching to column 5) If A260/230 remains low, perform an additional wash step or repeat the entire cleanup procedure