Neogen’s Red Stop Solution is a non-acidic, ready-to-use ELISA stop solution that contains no hazardous acids and can be used with our TMB substrates. Red Stop Solution does not increase background or optical density (OD) readings. Absorbance readings are taken at 650 nm within 2 hours of adding Red Stop Solution to the assay wells. Red Stop Solution offers a safer alternative to the traditional acids that are used to stop ELISA reactions. Available Products Red Stop For research and manufacturing use only.