Over-Washing Removes Bound Detection Reagents (ELISA (Signal Problems))

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Signal progressively decreases with increased wash steps or aggressive washing. Reducing wash stringency restores signal. Edge wells show lower signal than center wells. Common causes: 1) Excessive number of wash cycles removes weakly bound antibodies or detection complexes 2) High-pressure washing from manual pipetting or automated washer dislodges bound reagents 3) Extended wash incubation times allow dissociation of antibody-antigen complexes 4) Harsh detergent concentration in wash buffer disrupts antibody binding Solutions: 1) Reduce number of wash cycles to minimum recommended in protocol (typically 3-5 washes) 2) Decrease wash duration: use brief 30-60 second washes instead of prolonged incubations 3) Use gentle manual pipetting pressure; dispense wash buffer slowly against well wall rather than directly onto bound reagents 4) If using automated washer, reduce aspiration and dispensing pressure settings to 「gentle」 mode 5) Optimize wash buffer: reduce Tween-20 concentration from 0.1% to 0.05% if over-washing is suspected