Three-dimensional hierarchical porous biochar as an efficient adsorbent for simultaneous extraction of ametryn and benzo[a]pyrene from tea beverages

Background Limits on ametryn and benzo[a]pyrene in tea beverages are becoming more stringent. To enhance detection efficiency and reduce analysis costs, it is critical to develop mixed-mode extractants for these two analytes with substantial differences in properties concurrently. Biochar (BC) is increasingly being used in the preparation of mixed-mode adsorbents, but there is a challenge in balancing adsorption capacity against adsorption rate. Therefore, it is of great significance to explore mixed-mode adsorbents that can simultaneously adsorb or extract analytes with different properties, such as ametryn and benzo[a]pyrene, and achieve rapid adsorption or extraction. Results The shells of Zizyphus jujuba seeds were used to synthesize K-H-BC, a three-dimensional hierarchical porous BC with a wide range of oxygen-containing functional groups. The synthesis technique included KOH activation and modification using a 1:3 vol ratio of HNO 3 /H 2 SO 4 . K-H-BC's mixed-mode adsorption properties resulted in various interactions with ametryn and benzo[a]pyrene. It exhibited rapid adsorption rates for ametryn and benzo[a]pyrene (reaching equilibrium in 15 min and 5 min, respectively) as well as high adsorption capacities (487.64 mg g −1 and 133.16 mg g −1 , respectively). Using K-H-BC as a dispersed solid-phase extraction adsorbent, combined with high performance liquid chromatography, a method for simultaneously detecting the two analytes in tea beverages was established. Ametryn displayed a linear range of 2–500 μg L −1 with a limit of detection of 0.20 μg L −1 , while benzo[a]pyrene showed a linear range of 25–500 μg L −1 with a limit of detection of 2.12 μg L −1 . Significance and novelty It provides a solution to the problem of high hydrophobicity in KOH-activated BC by modifying it with mixed acids. K-H-BC possesses a three-dimensional hierarchical porous structure and abundant surface oxygen-containing functional groups, allowing it to retain high adsorption capacity during rapid adsorption while co-adsorbing and co-extracting analytes with significantly different properties. This research provides a reference for using BC in sample pretreatment and the comprehensive utilization of non-medicinal parts of Zizyphus jujuba .