Peroxide (e.g. hydrogen peroxide H2O2) is one of the key reactive oxygen species formed under oxidative stress conditions. High levels of peroxide formation have been linked to pathological conditions such as ageing, asthma, diabetes, atherosclerosis, cataract, inflammatory arthritis and neurodegenerative diseases. Simple, direct and automation-ready procedures for quantitative determination of peroxide find wide applications in research and drug discovery. BioAssay Systems' peroxide assay kit is designed to measure peroxide concentration in biological samples without any pretreatment. The improved method utilizes the chromogenic Fe3+-xylenol orange reaction, in which a purple complex is formed when Fe2+ provided in the reagent is oxidized to Fe3+ by peroxides present in the sample. The intensity of the color, measured at 540-610nm, is an accurate measure of the peroxide level in the sample. The optimized formulation substantially reduces interference by substances in the raw samples. This product is for Research Use only and is not intended for diagnostic purposes.