Determination of Carcinogenic Primary Aromatic Amines Contained as Impurities in Synthetic Organic Colorants.

This article focuses on the development and application of an analytical method to detect carcinogenic primary aromatic amines (PAAs) present as impurities in synthetic organic colorants. Using ultrasound extraction with hydrochloric acid containing 20% methanol, followed by alkaline conversion and diatomaceous earth column extraction, the method was applied to 38 colorants, revealing the presence of several PAAs—including 2,4-dimethylaniline, o-toluidine, and p-phenylazoaniline—at varying concentrations. Most detected PAAs corresponded to starting materials or intermediates in colorant synthesis, though p-phenylazoaniline in Yellow No. 407 appeared to be a synthesis byproduct. The study highlights that p-phenylazoaniline was consistently found at significant levels in Red No. 225 samples from multiple suppliers, underscoring the need for monitoring these impurities to enhance colorant safety.