Determination of Inorganic Bromides in Food Red No. 104 by Ion Chromatography

Abstract

An ion chromatographic method is described for the determination of inorganic bromides in Food Red No. 104 (R104; C.I. 45410, C.I. Acid Red 92).
Conductivity detection under acidic solvent conditions (2.5mM phthalic acid and 2.4mM tris (hydroxymethyl) aminomethane) was chosen from the viewpoint of sensitivity (determination limit: 0.5ppm). The bromide ion was separated satisfactorily on a column of Shim-pack IC-Al with a guard columm of Shim-pack IC-GAl at a flow rate of 1.5ml/min at 40°C and the recovery of NaBr (0.0644mg) added to R104 standard (100mg) was 101.5%.
Then, thirty-nine commercial samples of R104 made in Japan were analyzed by this method. All of the commercial R104 samples contained inorganic bromides above 0.01% (calculated as NaBr) and the highest and average contents were 0.329 and 0.159%, respectively. The bromide content average classified according to manufacturer showed large differences, taking account of the standard deviations. Since we observed an increase of inorganic bromides in a solution of R104 after storage without shielding from light, the differences might derive from the manufacturing conditions used by each maker during the synthesis of R104.