RP-HPTLC‒UV/VIS and RP-HPLC‒DAD determination of eight synthetic food dyes in alcoholic and soft drinks from the Romanian market

Two accurate and efficient reversed-phase methods, one by high-performance thin-layer chromatography with ultraviolet‒visible detection (RP-HPTLC‒UV/VIS) and the other by high-performance liquid chromatography with diode array detection (RP-HPLC‒DAD), for the simultaneous determination of eight synthetic food dyes (Tartrazine, Ponceau 4R, Sunset yellow FCF, Allura red AC, Brilliant blue FCF, Carmoisine, Quinoline yellow, and Patent blue V) in drinks with simple pretreatment were developed and applied to analyze some alcoholic and soft drinks. Detection was performed in the visible range in both cases at wavelengths (nm) of maximum absorbance (420 yellow, 500 red, or 630 blue), depending on the color of each dye. Both developed methods were validated for selectivity, linearity, limit of detection (LOD), limit of quantification (LOQ), intra- and interday precision, and recovery, with good results. The RP-HPTLC‒UV/VIS method showed linearity (R² > 0.998) in the 7–125 µg/mL calibration range, LOD of 0.27–0.92 µg/mL, LOQ of 0.82–1.49 µg/mL, intraday precision (%RSD) of 2.57–7.57, interday precision (%RSD) of 4.21–9.31, and recovery for alcoholic and soft drinks of 86.87–99.87% and 82.70–96.67%, respectively. The RP-HPLC–DAD method showed linearity (R² > 0.999) in the 1.56–50.0 µg/mL calibration range, LOD of 0.11–0.29 µg/mL, LOQ of 0.32–0.90 µg/mL, intraday precision (%RSD) of 0.13–2.15, interday precision (%RSD) of 0.30–2.47, and recovery of 98.17–101.30% and 88.13–101.9% for alcoholic and soft drinks, respectively. These methods were successfully applied to analyze the 8 synthetic food dyes in 11 (3 alcoholic and 8 soft) drinks from the Romanian market to verify compliance with the label and the maximum permitted level of food dyes in drinks to ensure food safety.