A hybrid material was prepared from graphene oxide and melamine sponge, and modified with phenylboronic acid to obtain a sorbent for the enrichment of the nucleosides cytidine, uridine, inosine, guanosine and adenosine. The loading capacity typically is around 27.8 mg g which is comparable to other sorbents, and highly selectivity for cis-diols is observed even if the concentration of potential interferents is 1500-fold higher. The sorbent was placed in an injector, and the process was operated semiautomatically by using a peristaltic pump. The sorbent is stable and can be re-used six times without decrease in efficiency. It was applied to the selective extraction of the cis-diols (cytidine, uridine, inosine, guanosine, adenosine) from HepG2 cells. It presents good linear between 3 to 5000 μg L and the limits of detection (in HPLC analysis with UV detection) are 1-4 μg L. Good recoveries of 85-101% were obtained with spiked HepG2 cells samples, with relative standard deviation of ≤9.9%. Graphical abstract Schematic for the preparation of boronic acid modified graphene oxide/melamine sponge composite for in-syringe solid-phase extraction of nucleosides.

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The films formed on the surface of copper during its anodic dissolution in the neutral or acidic sulfate solution were studied with the in-line digital holography. The results showed that the mixture films were formed on the surface of copper in the neutral or acidic sulfate solution: the inner oxide film and the outer salt film. Although there are defects in the oxide film caused by the sulfate ions, the oxide film other than the salt film mainly inhibits the anodic dissolution at the high anodic potentials.

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