Determination of 13 synthetic food colorants in water-soluble foods by reversed-phase high-performance liquid chromatography coupled with diode-array detector

A reversed-phase high performance liquid chromatographic method for the successful separation and determination of 13 synthetic food colorants (Tartrazine E 102, Quinoline Yellow E 104, Sunset Yellow E 110, Carmoisine E 122, Amaranth E 123, Ponceau 4R E 124, Erythrosine E 127, Red 2G E 128, Allura Red AC E 129, Patent Blue V E 131, Indigo Carmine E 132, Brilliant Blue FCF E 133 and Green S E 142) was developed. A C18 stationary phase was used and the mobile phase contained an acetonitrile-methanol (20:80 v/v) mixture and a 1% (m/v) ammonium acetate buffer solution at pH 7.5. Successful separation was obtained for all the compounds using an optimized gradient elution within 29 min. The diode-array detector was used to monitor the colorants between 350 and 800 nm. The method was thoroughly validated. Detection limits for all substances varied between 1.59 (E 142) and 22.1 (E 124) μg L⁻¹. The intra-day precision (as R.S.D._r) ranged from 0.37% (E 122 in fruit flavored drink at a concentration of 100 mg L⁻¹) to 4.8% (E 142 in icing sugar at a level of 0.9 mg kg⁻¹). The inter-day precision (as R.S.D._R) was between 0.86% for E 122 in fruit flavored drink at 100 mg L⁻¹ and 10% for E142 in jam at a concentration of 9 mg kg⁻¹. Satisfactory recoveries, ranging from 94% (E 142 in jam) to 102% (E 131 in sweets), were obtained. The method was applied to the determination of colorants in various water-soluble foods, such as fruit flavoured drinks, alcoholic drinks, jams, sugar confectionery and sweets, with simple pre-treatment (dilution or water extraction).