Spectrophotometric Determination for 10^<-8> M Levels of L-Ascorbic Acid Using the Diazotization of 5,10,15,20-Tetrakis(4-aminophenyl)porphine

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A water-soluble porphyrin having four aminophenyl groups 5,10,15,20-tetrakis(4-aminophenyl)porphine (TAPP) diazotizes with nitrite ion and produces a large spectral change (ε : molar absorptivity, Δε=ε_<sample>-ε_<blank>=3.0×10^5M^<-1>cm^<-1>, 434nm). The coexistence of L-ascorbic acid (AsA) strongly interferes with this reaction. Therefore, a highly sensitive spectrophotometric determination of AsA was developed using this effect. For the determination of trace amounts of AsA, the calibration curve was linear in the concentration range of 8.0×10^<-8>M-5.0×10^<-7>M (14-88ppb). The detection limit (3σ) was 1.0×10^<-8>M (1.76ppb), and the relative standard deviation was 1.86% (2.0×10^<-7>M (35ppb) AsA, 6 determinations). This method is more than 20 times highly-sensitive than the indophenol method as standard spectrophotometry for AsA. This method has been applied to the deternation of AsA in soft drinks and drugs.
公益社団法人日本薬学会の論文
1997-08-15