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4-Nitrophenyl phosphate disodium salt hexahydrate


p-Nitrophenyl phosphate disodium hexahydrate, Disodium 4-nitrophenyl phosphate hexahydrate, di-Sodium 4-nitrophenyl phosphate, pNPP disodium hexahydrate
Linear Formula:
O2NC6H4OP(O)(ONa)2 · 6H2O
CAS Number:
Molecular Weight:
EC Number:
MDL number:
PubChem Substance ID:



Quality Level


water: 1 tablet/3 mL, clear, colorless

storage temp.


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InChI key


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General description

Chromogenic substrate for the determination of acid and alkaline phosphatases. The reaction produces a soluble end product that is yellow in color. The reaction may be stopped with 3 N NaOH and read at 405 nm.


4-Nitrophenyl phosphate disodium salt hexahydrate has been used in enzyme-linked immunosorbent assay (ELISA) as a substrate for streptavidin-Alkaline Phosphatase. It has also been used as a substrate in control assay for comparing 4-aminophenyl phosphate/diethanolamine (APP/DEA) assay for alkaline phosphatase.

Biochem/physiol Actions

4-Nitrophenyl phosphate disodium salt hexahydrate (pNPP) is a non-proteinaceous and non-specific substrate for determining protein tyrosine phosphatase activity. Hydrolysis of pNPP yields p-nitrophenol. pNPP is a common chromogenic substrate for alkaline phosphatase.


Contains 15 mg substrate per tablet

Storage Class Code

11 - Combustible Solids



Flash Point(F)

Not applicable

Flash Point(C)

Not applicable

Personal Protective Equipment

dust mask type N95 (US), Eyeshields, Gloves

Certificate of Analysis

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Certificate of Origin

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Alkaline Phosphatase Assay Based on the Chromogenic Interaction of Diethanolamine with 4-Aminophenol
Sun J, et al.
Analytical Chemistry, 90(10), 6339-6345 (2018)
Protein tyrosine phosphatase assays
Lorenz U
Current Protocols in Immunology, 93(1), 11-17 (2011)
Masaya Yokota et al.
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Colorimetric Alkaline Phosphatase and Peroxidase Substrate Detection Systems

Nitroblue Tetrazolium (NBT) is used with the alkaline phosphatase substrate 5-Bromo- 4-Chloro-3-Indolyl Phosphate (BCIP) in western blotting and immunohistological staining procedures. These substrate systems produce an insoluble NBT diformazan end product that is blue to purple in color and can be observed visually.

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