Peroxide Quantitative Assay Kit (Water compatible): This Water-compatible Quantitative Assay Kit uses a Colorimetric Assay to detect peroxide based on oxidation of ferrous to ferric ion in the presence of xylenol orange. Peroxide first reacts with sorbitol which enhances sensitivity by converting it to a peroxyl radical, this in turn initiates Fe2+ oxidation to Fe3+ at acidic pH, and the Fe3+ complexes with the xylenol orange dye to yield a purple product with maximum absorbance at 560 nm. The complex displays maximal absorption between 540 and 580 nm, but also absorbs measurably up to 620 nm. When using microplates, the preferred wavelength for measurement is 595 nm (best signal-to-noise). The maximum absorbance of the assay components before addition of peroxide is at 430 nm. The kit is suitable for H2O2 measurement in many cellular assays, including quantitating detergent peroxide and monitoring cellular activity.