Poor Dynamic Range Between Signal and Background (ELISA (R&D Guide))

Question

Accepted Answer

The difference between maximum signal (high standards) and background (blank wells) is compressed, typically less than 5-fold, making it difficult to distinguish between samples of different concentrations. Common causes: 1) HRP-conjugate concentration too low or detection antibody too dilute 2) Substrate incubation time insufficient for colorimetric development 3) Plate reader using incorrect wavelength (wrong filter for chromogen or fluorochrome) 4) Capture antibody did not bind well to plate (tissue culture plate used or coated in protein-containing buffer) 5) Standard curve dilutions calculated incorrectly Solutions: 1) Check and optimize HRP-conjugate and detection antibody dilutions through titration 2) Extend substrate incubation time (typically 15-30 min for TMB until blue color develops) 3) Verify plate reader wavelength matches protocol specification (e.g. 450 nm for TMB, 405 nm stop) 4) Use ELISA-validated plates; dilute capture antibody/antigen in PBS without additional protein (no BSA/serum) 5) Recalculate and prepare fresh standard curve; verify serial dilution accuracy