Failure Case Library

Real lab failures, root causes, and fixes — curated and bilingually annotated by our team.

All Techniques (6) PCR (Sigma Guide) (12) End-point PCR Primers (9) Western Blot (9) Wound Healing Assay (5) Cell Culture (Contamination) (7) Lipid Transfection (8) CCK-8 Cell Viability Assay (5) Colony Formation Assay (10) Transfection (8) Nucleic Acid Quantification (9) Transfection (Co-transfection) (1) Protein Extraction (4) Plasmid Construction (Double Digest) (1) Sanger Sequencing (2) Plasmid Construction (1) qPCR (RT-qPCR) (5) Transwell Migration / Invasion Assay (5) Immunohistochemistry (IHC) (6) PCR (Polymerase Chain Reaction) (26) Restriction Enzyme Digest (13) DNA Cleanup & Plasmid Purification (7) RNA Cleanup (4) NGS Library Preparation (NEBNext Ultra II) (7) HMW DNA Extraction (Monarch) (7) LAMP (Loop-mediated Isothermal Amplification) (7) RNA Depletion for RNA-seq (7) Bacterial rRNA Depletion (4) Cell-free DNA Extraction (8) ELISA (Competitive) (18) ELISA (Signal Problems) (11) ELISA (High Background) (8) ELISA (Inconsistent Results / High CV) (6) ELISA (Standard Curve Fit Problems) (6) Western Blot (Weak / No Signal) (6) Western Blot (Detection Problems) (7) Western Blot (Bands at Wrong MW) (5) Western Blot (Misshapen / Uneven Bands) (5) Western Blot (Unexpected Multiple Bands) (7) Western Blot (Unusual Gel Band Appearance) (3) ChIP (High Background) (1) ChIP (Low Resolution with High Background) (6) ChIP (Low Signal) (8) ChIP (PCR Amplification Problems) (4) Immunohistochemistry (High Background) (9) Immunohistochemistry (No Staining) (9) Immunoprecipitation (High Antibody Elution) (1) Immunoprecipitation (High Background) (8) Immunoprecipitation (No Protein Detected) (5) Immunoprecipitation (Protein Obstruction) (1) ELISPOT (8) Tissue Imaging (Autofluorescence) (9) Flow Cytometry (Troubleshooting) (8) ELISA Development (9) Flow Cytometry (Autofluorescence) (7) Flow Cytometry (Compensation) (7) Flow Cytometry (Fc Blocking) (7) Flow Cytometry (Fixation & Permeabilization) (9) Flow Cytometry (Isotype Controls) (7) Flow Cytometry (Fixation Buffers) (7) Western Blot (CST Guide) (8) ChIP (CST Guide) (8) Immunoprecipitation (CST Guide) (14) Immunohistochemistry (CST Guide) (14) Flow Cytometry (CST Guide) (8) ELISA (R&D Guide) (10) ELISA (Sigma Guide) (6) Western Blot Immunodetection (19) IP-Western Blot (6) Flow Cytometry (Sample Considerations) (14) Flow Cytometry (Paraformaldehyde Fixation) (14) Western Blot (Sigma Protocol) (8) PCR / RT-PCR Amplification Problems (5) Cell Culture (Cell Death) (8) Cell Culture (Precipitates) (6) PCR (Invitrogen Guide) (8) PCR / qPCR Plastics (9) Flow Cytometry (Controls) (8) Plasmid Mini-prep (1) Transfection (siRNA Knockdown) (1) Western Blot (Blue Background) (1)
ELISA (Sigma Guide) moderate

Unexpected or Inconsistent Assay Results

Sample quantification values are outside expected biological range, controls fail to meet acceptance criteria, or results are not reproducible between runs despite similar experimental conditions.

💡 5 causes ✓ 5 fixes
ELISA (Sigma Guide) critical

No Signal or Weak Signal in ELISA

The ELISA plate reader detects no colorimetric signal or signal intensity is significantly below expected values after substrate development. Wells appear clear or only faintly colored even after standard incubation times of 10-30 minutes.

💡 6 causes ✓ 6 fixes
ELISA (Sigma Guide) critical

Poor or Non-Linear Standard Curve

Standard curve shows irregular shape, poor linearity, or inconsistent serial dilution response. R-squared value below 0.95 or curve does not follow expected sigmoidal or linear pattern across dynamic range.

💡 5 causes ✓ 5 fixes
ELISA (Sigma Guide) severe

Uneven Color Development Across Plate

Color intensity varies significantly between wells that should be identical. Pattern may show edge effects, gradients across the plate, or random spotty appearance indicating incomplete or inconsistent reagent contact.

💡 4 causes ✓ 4 fixes
ELISA (Sigma Guide) severe

Poor Reproducibility Between Duplicate Wells

Coefficient of variation (CV) between duplicate or triplicate wells exceeds 10-15%. Individual replicates show inconsistent absorbance values that cannot be attributed to biological variation.

💡 4 causes ✓ 4 fixes
ELISA (Sigma Guide) severe

High Background Signal in ELISA

All wells including negative controls show elevated absorbance readings. Background signal obscures specific signal, reducing signal-to-noise ratio and making data interpretation difficult.

💡 6 causes ✓ 6 fixes