Abstract: A Prussian blue/zinc oxide-carbon nanotube composite is provided, the nanotube composite being selective and sensitive for detection of hydrogen peroxide, which is important for screening for early cancer detection, monitoring cardiovascular disease, detecting onset of food spoilage, and enzymatic reactions that produce hydrogen peroxide as a byproduct. Also provided are methods using said zinc oxide-carbon nanotube composite in which standard addition is used in combination with chronoamperometry detection to quantify the level of hydrogen peroxide in a biological sample.