I'd be grateful for the molar extinction coefficient ε of azorubine at the absorption maximum (about 520 nm), with an authoritative reference.


Found the following value (see the very comprehensive reference below):

molar absorption coefficient $\pu{\epsilon = 24 000 M-1 cm-1}$ ($\pu{510 nm}$) in water

CARMOISINE (E122), CAS Number 3567-69-9, (3~{E})-4-oxo-3-[(4-sulfonaphthalen-1-yl)hydrazinylidene]naphthalene-1-sulfonic acid, SMILES(canonical): C1=CC=C2C(=C1)C(=CC=C2S(=O)(=O)O)NN=C3C=C(C4=CC=CC=C4C3=O)S(=O)(=O)O,


Taniguchi, M. and Lindsey, J. S. (2018), Database of Absorption and Fluorescence Spectra of >300 Common Compounds for use in PhotochemCAD. Photochem Photobiol, 94: 290-327. doi:10.1111/php.12860 https://onlinelibrary.wiley.com/doi/epdf/10.1111/php.12860

Originally from

  1. Kamachi, S., K. Wakabayashi, K. Zaitsu and Y. Ohkura (1983) New chromogenic substrates for the assy of esterases — acetates and butyrates of phenolic naphthylazo compounds with sulfonic acid group. Chem. Pharm. Bull. 31, 162–167.

  2. Lin, J.-J., D. Liu, C. Fu and T.-Z. Li (2012) Optimization of Fenton-like degradation conditions of Acid Red 14 azo dye under low frequency ultrasonic irradiation. Asian J. Chem. 24, 4453– 4457.

  3. Arvin, M., G. Dehghan, M. A. Hosseinpourfeizi and A. A. Moosavi- Movahedi (2013) Spectroscopic and electrochemical studies on the interaction of carmoisine food additive with native calf thymus DNA. Spectrosc. Lett. 46, 250–256.


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