Boronate functionalized magnetic nanoparticles and off-line hyphenation with capillary electrophoresis for specific extraction and analysis of biomolecules containing cis-diols

In recent years, functionalized magnetic nanoparticles (MNPs) have drawn continuously increasing attention due to their great potential for capturing biological molecules or species. However, functionalized MNPs as nanoextraction probes and the coupling with a separation platform for chemical analysis have not extensively investigated yet. In this study, boronate functionalized MNPs were synthesized and employed as extracting probes to capture and enrich cis-diol-containing biomolecules, and an off-line coupling method of the MNPs-based extraction with capillary electrophoresis (CE) was established by using pH junction, an on-line preconcentration technique in CE, as a bridge for the coupling. The prepared MNPs exhibited specific selectivity and sufficient capacity. The pH junction compressed a large injected sample volume into a much narrower sample zone and therefore significantly improved the detection sensitivity, solving the sensitivity mismatch between the MNPs-based extraction and CE. Experimental conditions for the pH junction and the desorption were optimized. Under the optimized conditions, the sensitivity was enhanced by 42-fold as compared with regular CE. N,N-dimethylformamide was found to be an effective desorption promoter, which reduced the desorption time to a few minutes. With the established method, riboflavin in a human urine sample was determined.