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SIGMAFAST p-Nitrophenyl phosphate Tablets

tablet, To prepare 20 mL

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pNPP tablets
EC Number:
MDL number:

Quality Level




water: 0.25 tablet/mL, clear, colorless

storage temp.


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Developed for use as a soluble substrate for the detection of alkaline phosphatase activity in Enzyme Immunoassays (EIA). pNPP is the substrate of choice in high sensitivity alkaline phosphatase-based EIA assays.One pNPP tablet and one Tris buffer tablet are dissolved in deionized water and provide a ready-to-use substrate. Each Sigma FAST pNPP tablet set yields a solution containing 1.0 mg/ml pNPP, 0.2 M Tris buffer. EIA applications using pNPP may be read in timed assays or stopped with 3N NaOH for delayed readings. SIGMAFAST require only the addition of distilled or deionized water to prepare an active substrate solution. Tablets are individually packaged in foil packets.


Each tablet set dissolved in 20 mL deionized water yields a ready-to-use buffered solution containing pNPP.

Legal Information

SIGMAFAST is a trademark of Sigma-Aldrich Co. LLC

Storage Class

11 - Combustible Solids




Not applicable


Not applicable

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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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