Abstract

A hierarchical composite ZnO@Carbon foam/PVA cryogel was fabricated and applied to extract and enrich parabens and synthetic phenolic antioxidant. A hierarchical porous structure was produced by embedding CaCO<inf>3</inf> in the porous PVA cryogel and then removing the CaCO<inf>3</inf> with hydrochloric acid, which generated CO<inf>2</inf> bubbles. The extracted compounds were quantitatively determined by high performance liquid chromatography (HPLC). The ZnO@Carbon foam loading, elution solvent type and volume, sample flow rate, sample volume, ionic strength and sample pH were optimized. The developed method demonstrated linear responses in the range of 0.25–1000.0 μg L⁻¹ for propyl paraben and butyl paraben, 0.50–1000.0 μg L⁻¹ for methyl paraben and 2.00–1000.0 μg L⁻¹ for tert-butylhydroquinone, with R² above 0.99. For the four analytes, the limits of detection (LOD) and limits of quantification (LOQ) ranged from 0.25 to 2.0 μg L⁻¹ and from 0.75 to 5.0 μg L⁻¹, respectively. The fabricated porous composite sorbent was used to extract and enrich parabens and a synthetic phenolic antioxidant from fruit juice samples. Relative recoveries were in the range of 83.8–99.0% and the RSDs were lower than 6.0%. The enrichment factor of the developed method ranged from 12.5 to 14.9. Low concentrations of tert-butylhydroquinone and butyl paraben were found in some samples at 2.20 and 2.52 μg L⁻¹, respectively. Repeatability was evaluated in terms of intra-day precision and inter-day precision. RSDs were in the range of 2.1–3.0% and 3.5–4.5%, respectively. The developed sorbent was easy to fabricate, and could be reused up to 12 times.