pNPP Powder (Novex®) pNPP may be used as a substrate for alkaline phosphatase (AP) in enzyme immunoassays. Substrate: pNPP Product Size: 6 x 1 mL Substrate Type: AP (Alkaline Phosphatase) Substrate Detection Method: Colorimetric Substrate Properties: Chemical Substrate Shipping Condition: Wet Ice Regulatory Statement: For Research Use Only. Not for use in diagnostic procedures. Store at 2-8°C