Thermo Scientific Pierce PNPP (p-Nitrophenyl Phosphate, Disodium Salt) is a colorimetric, soluble substrate of alkaline phosphatase for use in ELISA applications. When alkaline phosphatase and PNPP are reacted, a yellow water-soluble reaction product is formed. This reaction product absorbs light at 405 nm.

Features of PNPP (p-nitrophenyl phosphate):
• One-component alkaline phosphatase (AP) substrate
• Absorbance maximum of 405 nm
• Develops a yellow hue in solution upon reaction with AP
• Safer to use—contains a non-mercury, non-azide preservative

The substrate is offered in several formats:
PNPP Substrate
• Powder Form

PNPP Substrate Tablets
• 5 mg tablets with an inert filler as the balance

PNPP Substrate Kit
• PNPP tablets and a Diethanolamine Buffer to yield more than one liter of substrate. The Diethanolamine Substrate Buffer (Cat. No. 34064) is also provided individually as a 5X concentrate.

1-Step™ PNPP Substrate Solution
• Circumvents this time-consuming and variable introducing step by providing a single component PNPP substrate. This substrate is stable for 12 months at 2–8°C and can be stopped with conventional methods.