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Prepared at the 30th JECFA (1986), published in FNP 37 (1986) and in FNP 52 (1992) |
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SYNONYMS |
CI Food Green 3, FD&C Green 3, CI (1975) No. 42053, INS No. 143 |
DEFINITION |
Consists essentially of disodium 3-[N-ethyl-N-[4-[[4-[N-ethyl-N-(3-sulfonatobenzyl)amino]phenyl](4-hydroxy-2-sulfonatophenyl)methylene]-2,5-cyclohexadien-1-ylidene]ammoniomethyl]benzenesulfonate and isomers and subsidiary colouring matters together with water, sodium chloride and/or sodium sulfate as the principal uncoloured components.
May be converted to the corresponding aluminium lake in which case only the General Specifications for Aluminium Lakes of Colouring Matters apply. |
Chemical names |
Disodium 3-[N-ethyl-N-[4-[[4-[N-ethyl-N-(3-sulfonatobenzyl) amino] phenyl](4-hydroxy-2-sulfonatophenyl)methylene]-2,5-cyclohexadien-1-ylidene] ammoniomethyl]-benzenesulfonate;
Inner disodium salt of N-ethyl-N-[4[[4-ethyl[(3-sulfophenyl)methyl]amino]phenyl](4-hydroxy-2-sulfophenyl) methylene]-2,5-cyclohexadien-1-ylidene]-3-sulfobenzene-methanaminium hydroxide |
C.A.S. number |
2353-43-9 |
Chemical formula |
C37H34N2Na2O10S3 |
Structural formula |  |
Formula weight |
808.86 |
Assay |
Not less than 85% total colouring matter |
DESCRIPTION |
Red to brown-violet powder or crystals |
FUNCTIONAL USES |
Colour |
CHARACTERISTICS | |
IDENTIFICATION | |
Solubility |
Soluble in water; sparingly soluble in ethanol |
Identification of colouring matters |
Passes test |
PURITY | |
Loss on drying at 135o together with chloride and sulfate calculated as sodium salts |
Not more than 15% |
Water insoluble matter |
Not more than 0.2% |
Chromium |
Not more than 50 mg/kg |
Arsenic |
Not more than 3 mg/kg |
Lead |
Not more than 10 mg/kg |
Heavy metals |
Not more than 40 mg/kg Test 0.5 g of the sample as directed in the Limit Test |
Subsidiary colouring matters |
Not more than 6% See description under TESTS |
Organic componds other than colouring matters |
Not more than 0.5%, sum of 2-, 3-, and 4-Formylbenzenesulfonic acids, sodium salts Not more than 0.3%, sum of 3- and 4-[N-Ethyl-N-(4-sulfophenyl)amino]methylbenzenesulfonic acid, disodium salts Not more than 0.5% of 2-Formyl-5-hydroxybenzenesulfonic acid, sodium salt Proceed as directed under Column Chromatography, using, for example, the following absorptivities: 3-formylbenzenesulfonic acid: 0.495 mg L-1 cm-1 at 246 nm in dilute HCl 3-[(ethyl)(4-sulfophenyl)amino]methylbenzenesulfonic acid: 0.078 mg L-1 cm-1 at 277 nm in dilute ammonia 2-formyl-5-hydroxybenzenesulfonic acid: 0.080 mg L-1 cm-1 at 335 nm in dilute ammonia |
Leuco base |
Not more than 5.0% Weigh accurately 130±5 mg sample and proceed as directed under Leuco Base in Sulphonated Triarylmethane Colours Absorptivity (a) = 0.6 mg L-1 cm-1 at approx. 625 nm Ratio = 0.971 |
Unsulfonated primary aromatic amines |
Not more than 0.01% calculated as aniline |
Ether extractable matter |
Not more than 0.4% |
TESTS | |
PURITY TESTS | |
Subsidiary colouring matters |
Prepare a 1% solution of the colour. By means of a syringe spot as a band 1 mg of the colour on an 20 x 20 cm silica gel thin layer chromatographic plate. Allow the plate to dry about 20 min in the dark before placing it in a chromatographic tank containing the following developing solution: acetonitrile/isoamyl alcohol/methyl ethyl ketone/water/ammonia (50/50/15/10/5 by volume). Develop the plate until the solvent front is near the top of the plate. Remove the plate and allow it to dry. The subsidiary colours will appear in the following positions: the two top bands are the lower sulfonated subsidiary colours followed by the isometric and the main band or fast Green FCF near the bottom of the plate. Scrape off all the bands above the isometric colour. Extract the colour from the silica gel with ethyl alcohol. Filter through a sintered glass funnel and examine spectrophotometrically. The Standard absorptivity of the lower subsidiary colour is 0.126 mgL-1cm-1.
NOTE: In the calculation of the subsidiary colour, it is assumed that its absorptivity at its peak is the same as that of the parent compound at its peak. Standard solutions must be prepared and their absorptivities measured within 1 h. Spectrophotometric measurements of the extracted subsidiary colours must be made as promptly as possibile. |
METHOD OF ASSAY |
Proceed as directed under Total Content by Titration with Titanous Chloride, using the following: Weight of sample: 1.9 - 2.0 g Buffer: 15 g sodium hydrogen tartrate Weight (D) of colouring matters equivalent to 1.00 ml 0.1 N TiCl3: 40.45 mg |