Determination of total non‐sulphonated aromatic amines in soft drinks and hard candies by reduction and derivatization followed by high‐performance liquid chromatography

Abstract

Utilizing elements of methodology developed previously for food colours, total free and bound non‐sulphonated aromatic amines (NSAA) were determined in commercial samples of soft drink beverages and hard candies. Bound amines in the samples were reduced using sodium dithionite, then total NSAA were extracted into chlorofom, transferred to aqueous acid solution and diazotized with sodium nitrite before coupling with 2‐naphthol‐3,6‐disulphonic acid, disodium salt (R‐salt). The coloured derivatives were analysed using reversed‐phase ion pair high‐performance liquid chromatography (HPLC) and an absorbance detector set at 512 nm. Solid phase extraction cartridges were utilized for extraction and clean‐up of the food colours present in the sample, and the concentration of each dye was determined quantitatively using HPLC and absorbance detector wavelengths of 426, 516 or 625 nm. Levels of total NSAA were compatible with those observed previously in food colours. Commercial soft drinks were found to contain (expressed in terms of total free plus bound NSAA in the beverage) 0.19–12.6 ng/ml of aniline, 0.83–8.25 ng/ml 1‐naphthylamine and 0.62–1.12 ng/ml 2‐naphthylamine. Levels of 0.66–9.15 ng/g of aniline and 2.48–10.6 ng/g 1‐naphthylamine were found in commercial samples of hard candies. Bound NSAA in hard candies appeared to survive the manufacturing process. Recoveries averaged 96.9% for tartrazine and 89.6–97.2% for the bound amines when hard candies were prepared in the laboratory.

Keywords:

• total non‐sulphonated aromatic amines
• food colours
• soft drinks
• hard candies
• reduction
• HPLC