Determination of total non‐sulphonated aromatic amines in the food colour amaranth by dithionite reduction followed by derivatization and high‐performance liquid chromatography

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Abstract
A method is reported for determination of total free and bound non‐sulphonated aromatic amines (NSAA) in the food colour amaranth. Bound amines are first reduced using sodium dithionite then all NSAA are extracted into chloroform, followed by transfer to aqueous acid solution, diazotization with sodium nitrite and subsequent coupling with 2‐naphthol‐3, 6‐disulphonic acid, disodium salt (R‐salt). The coloured derivatives are then analysed by reversed‐phase ion‐pair liquid chromatography using an absorbance detector at 522 nm. Samples of amaranth were spiked with various amounts of 1‐ and 2‐naphthylamine and recoveries ranged from 80 to 100% with deviations of less than 2%. A survey of commercial amaranth samples indicated that the dye may contain up to 435 μg/g of total 1‐naphthylamine and 214 μg/g of total 2‐naphthylamine. The majority of NSAA are bound to R‐salt during the manufacturing process and less than 5% remain in the free state in the dye.