A composite polymer of polystyrene coated with poly(4-vinylpyridine) as a sorbent for the extraction of synthetic dyes from foodstuffs

Abstract

A poly(St-co-EGDMA)@poly(4-vinylpyridine-co-EGDMA) composite polymer was synthesised by precipitation reversible addition–fragmentation chain transfer (RAFT) polymerization. The polymer was investigated as a sorbent for extraction of synthetic food dyes: ponceau 4R, tartrazine, sunset yellow, brilliant blue and erythrosine from soft drinks. The morphology and composition of the polymer were characterized and confirmed respectively by scanning electron microscopy and Fourier-transform infrared spectroscopy. The pH dependence experiment revealed that the adsorption of food dyes by the polymer was pH dependent and the maximum adsorption was achieved at pH 3. Adsorption between the polymer and the dyes was mainly due to electrostatic interaction. Under the optimized pH conditions, the polymer was saturated with the dye solutions at a concentration of about 200 μg mL⁻¹ and exhibited a maximum adsorption capacity of 9 μg mg⁻¹. The values were higher than those for polyamide, a sorbent used in the standard method. The recovery from the real samples of the three spiked concentrations 10, 50 and 100 μg mL⁻¹ was respectively within the ranges of 83.2–107.2%, 94.5–110.7% and 79.2–111.5%, with a SD within ±4%. The sorbent could be reused more than 10 times with a recovery higher than 80%. The small volume requirement of the sample and sorbent during the sample pre-treatment, indicated that poly(St-co-EGDMA)@poly(4-vinylpyridine-co-EGDMA) was a potential material for food dye extraction in an environment-friendly and economical manner.