Rosocyanine

Fixed

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Rosocyanine is a dye which is formed from curcumin and borates.

Use

The color reaction between borates and curcumin is used for spectrophotometric determination of boron in foods or different materials. As a reactant for the boric acid, the dye is curcumin, the. , In some Curcuma species, particularly in Curcuma longa Linn found in the rhizome of turmeric and is obtained from it. The reaction is very sensitive and has even small amounts of boron after. The absorption maximum of 540 nm is rosocyanine, wherein the colorimetric measurement is carried out.

Schlumberger coined the term rosocyanine for the description of this red dye.

Forming rosocyanine is dependent on the reaction conditions. The reaction is preferably carried out in hydrochloric or sulfuric auerer solution. The dye is also formed under other conditions, except that in alkaline solution gradually decomposition. The reaction may be disturbed in the presence of silicate, fluoride, titanium, zirconium, molybdenum, tungsten and beryllium, as well as at higher pH values. In the solution of oxidizing agents present as nitrate, bromate, etc. must be removed before the determination, since they accelerate the decomposition of curcumin.

Rosocyanine formed as a chelate compound in an acidic solution of curcumin and boric acid in a ratio of 2: 1 Curcumin has a 1,3- diketone structure, and may therefore act as a chelating agent. Boric acid and its salts ( borates ) preferably form chelates with 1,3- diketones. Such boron complexes are referred to ( a 1,3,2- dioxaborine here ) as dioxaborines.

In rosocyanine the two curcumin molecules are not in the same plane but are rotated relative to each other. The same applies to the dye Rubrocurcumin that results from the reaction of curcumin with borates in the presence of oxalic acid.

To exclude the presence of other interfering substances in the atmosphere after the boron curcumin method, a variant has been developed in which 2,2-dimethyl- 1 ,3-hexanediol or 2 -ethyl- 1 ,3-hexanediol, in addition to a large extent in curcumin neutral solution is added to the solution to be determined boron. This intermediate forms a chelate between the boron and the 1,3- hexanediol derivative, which is then extracted from the aqueous solution with an organic solvent. After acidification of the organic phase Rubrocyanin forms as a red dye, which is determined colorimetrically.

Properties

Rosocyanine is as solid a dark green powder with metallic luster, in solution it forms deep red colored solutions. In water and in some organic solvents, the dye is almost insoluble in ethanol it is bad ( 0.01 %), but in pyridine, sulfuric acid and acetic acid more soluble (about 1 %). An alcoholic solution of rosocyanine red green color on addition of alkali temporarily deep blue.