title: High-purity 4-nitrophenol: purification, characterization, and specifications for use as a spectrophotometric reference material.
abstract: We describe specifications for high-purity 4-nitrophenol, which is suitable for spectrophotometric standardization. Such a reference material is needed in clinical enzymology to establish the proper molar absorptivity of 4-nitrophenol under final reaction conditions, particularly for measuring alkaline phosphatase activity in human serum. Some lots of 4-nitrophenol available commercially met these specifications, but several did not. The latter can be purified to meet our specifications by recrystallization or sublimation. The molar absorptivity of 4-nitrophenol (35 mumol/L) IN 10 mmol/L NaOH at 25 degrees C at 401 nm is 18380 +/- 90 L.mol-1.cm-1.
mesh_terms: D000469:Alkaline Phosphatase / Q000032:analysis; D002152:Calorimetry, Differential Scanning; D006867:Hydrolases / Q000032:analysis*; D007202:Indicators and Reagents; D009596:Nitrophenols / Q000302:isolation & purification*; D013053:Spectrophotometry; D013379:Substrate Specificity; D014867:Water / Q000032:analysis
chemical_list: D007202:Indicators and Reagents; D009596:Nitrophenols; D014867:Water; D006867:Hydrolases; D000469:Alkaline Phosphatase; C024836:4-nitrophenol