Digitally plotted graphene oxide-modified paper for syringe-assisted micro-solid-phase extraction of antiepileptic...

Graphene oxide (GO) has considerable potential as a sorbent for solid-phase extraction because it interacts strongly with aromatic compounds, yet practical use can be hindered by difficulties in handling GO powder and reproducibly immobilizing it on solid supports. Cellulose paper is an attractive low-cost substrate, although conventional coating methods may yield uneven deposition. Digital plotting offers a straightforward way to place GO onto paper with controlled deposition and without complicated chemical modification. Accordingly, this study addressed the need for a reproducibly fabricated GO-paper sorbent that could be incorporated into a simple flow-through micro-solid-phase extraction (μ-SPE) system for bioanalytical sample preparation.

GO-modified cellulose paper was prepared with a commercial digital plotter, providing uniform and reproducible sorbent substrates. Initial screening of ten aromatic organic compounds led to the selection of carbamazepine and oxcarbazepine as model analytes. The optimized conditions were pH 6.0-7.5, a 5-min extraction period, and two GO layers. For spiked rat blood, 1 mL of sample underwent protein precipitation with 80% acetonitrile before GO-based extraction, followed by elution with 500 μL of 1% formic acid in acetonitrile. Placing the GO-modified paper in a syringe filter holder enabled syringe-assisted flow-through μ-SPE, with sample passage completed in approximately 30 s. Analysis by sweeping-micellar electrokinetic chromatography yielded recoveries of 87.5 ± 4.0 to 90.3 ± 3.1% for carbamazepine and 85.5 ± 4.7 to 89.1 ± 3.6% for oxcarbazepine.

This work is novel in integrating digitally controlled GO deposition on cellulose paper with a syringe-assisted flow-through μ-SPE configuration. The resulting approach combines reproducible sorbent preparation with rapid sample handling, low sorbent and solvent requirements, and effective cleanup of pretreated blood samples. It therefore shows the potential of digitally fabricated GO-paper sorbents as a simple and accessible platform for bioanalytical sample preparation.