Edge and Drift Effects on ELISA Plate (ELISA (R&D Guide))

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Accepted Answer

Wells at the plate edges show systematically higher or lower absorbance than center wells, or a gradient pattern appears across the plate, affecting data quality especially for samples in edge positions. Common causes: 1) Plate not flat in reader, or instrument calibration issue (verify by flipping plate 180°) 2) Uneven laboratory temperature or environmental conditions during incubation 3) Solutions not equilibrated to room temperature before adding to wells 4) Considerable time interval elapsed during solution addition across the plate 5) Solution volume differs between wells due to evaporation during long incubation Solutions: 1) Verify plate is flat in reader; flip plate 180° and re-read to diagnose instrument vs. plate issue 2) Incubate plates in temperature-stable area away from drafts, direct sunlight, or HVAC vents 3) Equilibrate all solutions to room temperature (20-25°C) for 30 min before use unless protocol specifies otherwise 4) Prepare all samples and standards before starting assay; minimize time between first and last well addition (target <2 min for substrate) 5) Use plate sealers or low-evaporation lids for incubations >30 min; verify pipette calibration for volume accuracy