Standard Curve Plateau at High Concentration End (ELISA (Competitive))

Question

Accepted Answer

The top of the standard curve (high analyte concentration, low OD) shows a plateau with minimal signal change across multiple high-concentration standards, reducing dynamic range. Common causes: 1) Pipetting errors during standard curve serial dilution causing concentration inaccuracies 2) Excessive non-specific background masking the competitive displacement signal 3) Insufficient incubation time preventing equilibrium of competitive binding reaction 4) Maximum competition already achieved at lower concentrations than expected Solutions: 1) Verify accurate pipetting technique and use fresh standards prepared with calibrated pipettes 2) Review and reduce non-specific binding following background troubleshooting protocols 3) Increase competitive incubation time from 1 hour to 2 hours at room temperature or overnight at 4°C 4) Adjust standard curve range to include lower concentrations where competitive displacement is observable