Fabrication of a dendrimer-modified boronate affinity material for online selective enrichment of cis-diol-containing compounds and its application in determination of nucleosides in urine

Boronate adsorbents have been widely used in the extraction of cis-diol-containing molecules, but most do not have efficient capacity due to limited binding sites on their surface. In this work, a high binding capacity dendrimer-modified boronate affinity material (SiO2@dBA) was synthesized via introducing tris(2-aminoethyl)amine as branching points and using poly(amidoamine) as the main dendrimeric scaffold before modification by boronate groups. The high density of amino groups on the dendrimer supplied a large number of binding sites for modifying boronate groups. Thus the adsorption capacity (676.8 μmol g−1 for catechol, 771.3 μmol g−1 for dopamine, 770.0 μmol g−1 for adrenaline) of SiO2@dBA was greatly improved. Moreover, when coupled with large-volume injection and online column-switching solid phase extraction, SiO2@dBA was able to capture cis-diols from 10 000-fold interference and enrichment factors reached up to 497–514, which was 26- to 51-fold higher than those of analogous non-dendrimer materials. Especially, the proposed method exhibited a striking low limit of detection, 0.24 ng mL−1 for cytidine, 0.52 ng mL−1 for uridine, 0.37 ng mL−1 for guanosine, 0.67 ng mL−1 for adenosine. Finally, the method was successfully applied to online determination of trace nucleosides in healthy human urine. In conclusion, the prepared adsorbent has potential to effectively enrich a large range of trace cis-diol substances in real samples.