Product codeN013 NN
Chemical name2-Hydroxy-1-(2-hydroxy-4-sulfo-1-naphthylazo)-3-naphthoic acid
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NN is a colorimetric and chelatometric reagent for calcium (pH 12, λmax=470 nm) and UO22+ (λmax=570 nm, ε=1.36×105). Although NN is soluble in water, the solution is unstable and decomposes in a few minutes, especially in the presence of oxidative ions. Its proton dissociation constants are reported to be pKa2=9.26 and pKa3=13.67 (μ=0.1, 24ºC). An NN solution of 0.1% w/v in 50% aqueous methanol is stable for one week if stored in a cool and dark place. Ascorbic acid is used as a stabilizer of the NN stock solution. Al, Cu, Fe(III), and Ni interfere with the determination of calcium by NN and should be masked by KCN or triethanolamine.
1) K. Ueno, T. Imamura and K. L. Cheng, "Handbook of Organic Analitical Reagents 2nd Edition", CRC Press, 1992.
2) J. Patton and W. Reeder, "New Indicator for Titration of Calcium with (Ethylenedinitrilo) Tetraacetate", Anal. Chem., 1956, 28, 1026.
3) A. Itoh and K. Ueno, "Evaluation of 2-Hydroxy-1-(2-Hydroxy-4-Sulpho-1-Naphthylazo)-3-Naphthoic Acid and Hydroxynaphthol Blue as Metallochromic Indicators in the EDTA Titration of Calcium", Analyst, 1970, 95, 583.
Handling and storage condition
|Appearance：||Black purple powder|
|Solubility in NaOH solution：||To pass test (clear, blue to deep blue)|
|Absorbance：||0.600 - 0.800 (around 555 nm)|
|Sulfated ash：||≦ 0.20 %|
|Sensitivity：||To pass test|