Studies on the Determination of Water-soluble Chloride and Water-soluble Sulfate in Food Blue No. 1 Aluminium Lake

An improved method for determination of water-soluble chloride and water-soluble sulfate in food blue No. 1 aluminium lake (B-1 Lake) was developed. The reason for the very poor recovery of sulfate in B-1 Lake was found to be the adsorption of anions on the lake. In order to prevent sulfate adsorption, 0.1M phosphate buffer (pH7.0) was added. As the ratio of B-1 Lake to water decreased, the chloride content apparently increased. A constant value of chloride content in B-1 Lake (3.5%) was obtained by extrapolation.The preparation of test solution and the determination of Cl-, SO42- and I- in B-1 Lake were conducted as follows. Weigh 1.000g of Food B-1 Lake, add 10ml of 0.1M phosphate buffer (pH 7.0) and 90ml of water, and shake for 5 minutes in a mechanical shaker. After filtration, test the solution by ion-chromatography.A good recovery of sulfate was obtained by the proposed method. In a commercial B-1 Lake sample, chloride content was 3.2% and sulfate content was 2.7%, using this method. These values represent total contents of water-soluble chloride and water-soluble sulfate.