Application of solid-phase extraction and planar chromatography with diode-array detection to the qualitative and quantitative analysis of dyes in beverages

The objective of this study was the use of solid-phase extraction and planar chromatography with diode-array detection for analysis of dyes in beverages. The dyes were chromatographed in normal-phase systems on silica, diol, cyanopropyl, and aminopropyl layers and in reversed-phase systems on cyanopropyl, diol, aminopropyl, and octadecyl silica wettable with water. Reversed-phase chromatography was performed with different mobile phase modifiers (tetrahydrofuran, dioxane, methanol, acetonitrile, and acetone) at different concentrations, containing different amines, cationic and anionic ion-pair reagents, buffers, and ammonia, again at different concentrations. On the basis of the results obtained it was possible to choose the best systems for analysis of tartrazine and sunset yellow in beverages. Identification of the analytes was confirmed by the comparison of UV spectra of drink components with those of standards, by use of the diode-array densitometer.