Acta Pharm. 49 (1999) 211-216

HPLC investigation of the degradation of some artificial food colorants
in the presence of ascorbic acid

VESNA RIZOVA,¹ TRAJCE STAFILOV,^2* and KIRO STOJANOVSKI²

¹State Institute of Public Health, P.O.B. 577, 91001 Skopje, Macedonia
²Institute of Chemistry, Faculty of Science, St. Kiril and Metodij University, P.O.B. 162, 91001 Skopje, Macedonia  

The influence of the concentration of ascorbic acid on some food colorants solution degradation has been studied. For this purpose, some food colorants with naphtalenic structure such as Ponceau 4R, Amaranth, Allura Red, Carmoisine and Sunset Yellow, have been investigated. Rate constant (k), time of colorant half-life (t_1/2), as well as the type of the reaction kinetics have been determined. The ascorbic acid solution degradation and the degradation of the investigated colorants in the solutions with no ascorbic acid have been also monitored under the similar conditions. The colorants and the ascorbic acid have been determined by high performance liquid chromatography (HPLC) with diode array detector (DAD) and UV-Vis spectrometry. It has been found that with an increase in ascorbic acid concentration in the colorant solution, the value of the rate constant increases as well. Accordingly, the value of the colorant half-life decreases. The values of the rate constant were 2.00-2.57 times higher if the colorant degradation was run in the presence of 500 mg L^-1 of ascorbic acid compared with the presence of 100 mg L^-1 of ascorbic acid. In all the cases the first order kinetics has been established.

Keywords: food colorants, Ponceau 4R, Amaranth, Allura Red, Carmoisine, Sunset Yellow, ascorbic acid, degradation, rate constant, HPLC, UV-Vis spectrometry