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PCR/qPCR Contamination & NTC Amplification Triage

A containment-first workflow for "no-template control amplified."

Systematically distinguish contamination from primer-dimers and implement controls (separated areas, dedicated equipment, UNG/UDG carryover prevention) to restore trustworthy PCR/qPCR.

CommunitySubmitted by CommunityWork15 min
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INGREDIENTS

🔍Web

PROMPT

You are OpenClaw. Ask which controls are positive (NTC, extraction blank, or both) and what assay type (endpoint PCR vs qPCR). Walk the user through a contamination-first containment plan: zoning, dedicated pipettes, fresh aliquots, component swap sequence, and optional UNG/UDG. Provide a "run sheet" template that logs controls, lot numbers, and zones.

Pain point

NTC/negative controls amplify or show melt peaks, invalidating runs and spreading contamination risk.

Repro/diagnostic steps

  1. Record which controls are positive (NTC only? extraction blanks too?).
  2. Confirm product type: melt curve shape and/or gel band size vs expected.
  3. Map workflow zones: where master mix is made, where template is added, where amplicons are opened.

Root causes (common)

  • Carryover from prior PCR products (amplicon aerosol).
  • Cross-contamination via pipettes, tips, shared reagents, shared PPE.
  • Workflow fails to separate pre- and post-amplification areas.

Fix workflow

  1. Enforce physical separation of pre- vs post-amplification areas; dedicated pipettes/consumables.
  2. Rotate in fresh aliquots; replace reagents one-by-one to identify the source.
  3. Consider UNG/UDG carryover prevention if compatible with assay.
  4. Add routine negative controls (NTC + extraction blank) into every run until stable.

Expected result

  • NTC and extraction blanks remain clean across runs; positives amplify as expected.

References

  • https://www.thermofisher.com/tw/en/home/life-science/pcr/real-time-pcr/real-time-pcr-learning-center/real-time-pcr-basics/good-laboratory-practice-avoid-contamination-qpcr-experiments.html
  • https://www.thermofisher.com/io/en/home/life-science/pcr/real-time-pcr/real-time-pcr-learning-center/real-time-pcr-basics/real-time-pcr-troubleshooting-tool/gene-expression-quantitation-troubleshooting/amplification-no-template-control.html
  • https://www.idtdna.com/page/support-and-education/decoded-plus/could-your-pcr-be-affected-by-contamination
Tags:#pcr#qpcr#contamination#wet-lab#qa

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