Abstract
Titanium trichloride titration is employed as the official method of determination of coal-tar dyes permitted under the Japanese Food Sanitation Law. The method was modified to allow the use of automatic photometric titration. The major wavelength of the interference filter corresponded with the specific color of each coal-tar dye. The injection droplet volume, the time interval between an injection and the next injection and the temperature during titration were decided as 30μl, 3sec and 70°C, respectively.
When determination of Brilliant Blue FCF by the presented method was carried out repeatedly, the standard deviation was 0.31 and the coefficient of variation was 0.34%. In the determination of Fast Green FCF and Acid Red, the coefficients of variation were 0.19-0.34%.
When the determination of four Azo colors and Indigo Carmine by photometric titration were carried out, the standard deviation was 0.08-0.28 and the coefficient of variation was 0.09-0.33%.
The method presented here is simple, rapid and accurate, and should be useful for the determination of food coal-tar dyes.
