Elisa kit Summary of Research Questions

Troubleshooting ELISA experiments hinges on controlling variables. Most ‘failures’ stem from variations in operational details. The following is a summary of common causes and solutions organised by problem type, to help you pinpoint the issue quickly.

The calibration curve is poor (R² < 0.99)

Standard curves form the basis of quantitative analysis; problems usually arise due to inaccurate gradients or uneven reactions.

standard Dilution error: Insufficient dissolution or failure to mix thoroughly during ratio dilution. It is recommended to allow the solution to stand briefly centrifugation after dissolution, to use a new tip at each step, and to vortex thoroughly.

Inaccurate dispensing: pipette Not calibrated, or inconsistent dispensing speed or angle. Ensure regular calibration and maintain a vertical, steady motion when dispensing.

Fluctuations in incubation conditions: Failure to seal the plate may result in edge effects or temperature inconsistencies. Be sure to use sealing film and place it in a constant-temperature incubator (37°C ± 0.5°C).

Excessively high background signal (high OD value)

A high background level narrows the detection range, making it difficult to interpret weak positive results specimen.

Incomplete cleaning: This is the most common cause. Ensure that each well is filled with cleaning solution, soak for 30 seconds to 2 minutes, pat dry, and repeat 3–5 times.

Inadequate blocking: The blocking agent has failed to cover all non-specific binding sites. It is recommended to extend the blocking time (≥1 hour) or optimise the blocking solution (e.g. containing 5% skimmed milk powder + 0.1% Tween-20).

Excessive colour development time: the substrate has reacted for too long. Control the reaction time; once the peak on the standard curve has developed fully, stop the reaction immediately.

sensitivity Low, weak signal (low OD value)

If the target substance is present but cannot be detected, this is usually due to a loss of activity or an insufficient reaction.

Reagent inactivation or omission: enzyme Standard antibody or substrate repeatedly freeze-thaw failing, or omitted during the procedure. Reagents must be used by batch aliquot to avoid repeated use freeze-thaw, and the substrate must be strictly protected from light.

specimen Degradation or the presence of inhibitors: specimen Repeated freeze-thaw leads to antigen degradation, or the presence of NaN₃ inhibits HRP enzyme activity. specimen Should aliquot be stored at –80 °C; the use of specimen or reagents containing NaN₃ is strictly prohibited.

Insufficient incubation: the incubation period was too short or the temperature was too low. You may try extending the incubation time (e.g. overnight at 4 °C) or checking the temperature of the incubator.

reproducibility Poor (high CV value for multiple holes)

Variations in sample addition: Uneven addition rate or pipette tip loose fittings. It is recommended to use a calibrated pipette and to add samples from the same batch of specimen simultaneously to minimise time differences between wells.

Inconsistent force when washing and drying: the force applied when drying by hand may be too strong or too light. The item should be patted dry vertically with moderate force to prevent the composite material from falling off or residue.

Edge effect: Evaporation occurs more rapidly at the outer holes. Give priority to the central holes, or use sealing film sealing throughout.

Key details to avoid pitfalls

Beware of the ‘hook effect’: When the concentration of specimen is too high, it may actually lead to signal suppression (false negatives). If the result is abnormally low but the expected value is high, dilute specimen and retest.

specimen Contraindications: haemolysis specimen (haem protein with peroxide-like enzyme activity), hyperlipidaemia specimen and samples containing NaN₃ specimen will all seriously interfere with the results.

Consumables management: Any unused items (microplate) must be sealed with a desiccant to prevent moisture ingress; if crystals form in the concentrated washing solution, dissolve them in a 37°C water bath before use.

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Note: The information on the scientific research products above is for reference only!