Boronic acid-modified polyhedral oligomeric silsesquioxanes on polydopamine-coated magnetized graphene oxide for selective and high-capacity extraction of the catecholamines epinephrine, dopamine and isoprenaline

Amino-functionalized polyhedral oligomeric silsesquioxanes (POSS-8NH(2)) were covalently bound to the surface of polydopamine-coated magnetized graphene oxide. It was then reacted with 4-formylphenylboronic acid to prepare a cubic boronic acid-bonded magnetic graphene oxide adsorbent. The new adsorbent exhibits better selectivity and much higher adsorption capacity for ortho-phenols over adsorbents where small boronic ligands are directly bound to the surface of the material. It is shown to enable selective and faster enrichment of the catecholamines epinephrine (EP), dopamine (DA) and isoprenaline (IP) with high selectivity over many potential interferents that can occur in urine. The analytes were then quantified by HPLC with fluorometric detection. Under optimal conditions, response is linear (R-2 >= 0.9907), limits of detection are low (0.54-2.3 ng center dot mL(-1)), and reproducibility is acceptable (inter- and intra-day assay RSDs of <= 10.9%). The method was successfully applied to the determination of endogenous EP and DA and exogenous IP in urine samples.