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. Produces a dark purple-pink color for a minimum of 2 hours when added to the wells Non-acidic solution RTU (ready-to-use) Order Details Product # Product Description 301474 Red Stop Solution, 200 mL 301475 Red Stop Solution, 500 mL 301476 Red Stop Solution, 1 L For research use only.