Determination of eight synthetic dyes in foodstuffs by green liquid chromatography

Eight synthetic food colours were analysed by green liquid chromatography. Green liquid chromatography is an environmentally friendly technique which does not use organic solvents in the extraction procedure or in the chromatographic method. Analysis was carried out for the following colours: tartrazine (E102), indigotine (E132), Quinoline Yellow (E104), Ponceau 4R (E124), Sunset Yellow (E110), Brilliant Blue (E133), Allura Red (E129) and carmoisine (E122) in four different foods: cookies, coloured rice, saffron and fruit juice. The method was performed on an Eurospher-100 C8 (5 μm, 4.6 × 250 mm) column with ultraviolet (UV)-VIS detection and validated by determining the calibration lines, measurement of recovery, precision, and limits of quantification and detection (LODs and LOQs). LOD ranged from 0.04 mg kg⁻¹ for E102 to 1.00 mg kg⁻¹ for E122; LOQ ranged from 0.06 mg kg⁻¹ for E102 to 1.12 mg kg⁻¹ for E122. The levels of colours in foods were compared with Iranian National Standards, but only 7.5% of cookies, 30% of coloured rice, 8% of saffron and 12% of juice samples were in compliance with these standards. Tartrazine is prohibited in Iran, but it was found as the most prevalent food colour in the samples analysed. The results of these tests confirmed that HPLC avoiding the use of organic solvents is a suitable method and can be used for quantitative analyses or screening of food samples for synthetic food colours.