HPLC determination of carminic acid in foodstuffs and beverages using diode array and fluorescence detection.

Carmine extracted from cochineal insects is one of the most used natural colorings for beverages and other foods. Its active ingredient is carminic acid (7-β-D-glucopyranosyl-9,10-dihydro-3,5,6,8-tetrahydroxy-1-methyl-9,10-dioxo-2-anthracenecarboxylic acid). This work describes a rapid HPLC determination of carminic acid and compares diode array and fluorescence detections for quantification. Samples with higher protein levels, such as milk and yogurt, are first treated with 1 mL of 8 M NH₄OH (5 min), the pH is reduced to 2 with 6 M HCl before centrifugation, the supernatant is then filtered and injected into the chromatograph. Low protein samples are simply filtered before injection. The separations were performed with a LiChroCART RP18 column using a mixture of acetonitrile and formic acid as mobile phase. The optimized conditions permit baseline quantification of the carminic acid even in the presence of other coloring agents. The sampling and analytical procedures are considerably faster than those of the literature and present excellent recuperation, selectivity, accuracy and precision. The method was applied to analysis of several yogurts and beverages. [ABSTRACT FROM AUTHOR]