p-Phenylenediamine-modified graphene oxide as a sorbent for solid-phase extraction of phenylurea herbicides, nitroimidazoles, chlorophenols, phenylurea insecticides and phthalates.

Graphene oxide was covalently modified with p-phenylenediamine via a diazonium reaction. The resulting material was employed as a sorbent for the solid-phase extraction of six phenylurea herbicides (metoxuron, monuron, chlortoluron, isoproturon, monolinuron, and buturon) from environmental water and lettuce leafs. Some key factors that influence the extraction efficiency were studied, including sample loading rate, sample pH, and desorption conditions. Following desorption with acetonitrile, the analytes were quantified by HPLC with UV detection. Under optimized conditions, response to phenylurea herbicides is linear in the 2.0-100 ng mL-1 concentration range for water samples, and 5.0-100 ng g-1 for leaf lettuces. The limits of detection are 0.10-0.25 ng mL-1 for water samples, and 1.5-2.5 ng g-1 for leaf lettuces. The sorbent was also applied to the preconcentration of organic compounds including nitroimidazoles, chlorophenols, phenylurea insecticides and phthalates. This shows that this sorbent has a large potential for the enrichment of organic pollutants. Graphical abstract A graphene oxide/p-phenylenediamine (GO@PA) composite was prepared via a simple and environmentally-friendly diazonium reaction between p-phenylenediamine diazonium salt and graphene oxide. It was used as the solid phase extraction (SPE) adsorbent to extract phenylurea herbicides with the extraction efficiency higher than that of commercial C18, multi-walled carbon nanotube and polystyrene polymer. The SPE method was combined with HPLC for simultaneous determination of six phenylurea herbicides in environment water and vegetable samples.