Preparation of phenyl-boronic acid polymeric monolith by initiator-free ring-opening polymerization for microextraction of sulfonamides prior to their determination by ultra-performance liquid chromatography-tandem mass spectrometry.

In this study, a novel phenyl-boronic acid polymeric monolith (PBAPM) in polyether ether ketone (PEEK) tube was fabricated. The inner wall of PEEK tube was modified with mussel inspired polydopamine layer to firmly bond PBAPM, so as to avoid the outflow of PBAPM from PEEK tube and improve the service life and application scope of PBAPM. The PBAPM was synthesized by initiator-free ring-opening polymerization based on our previous work. The boric acid groups provided B-N coordination sites, as well as the hydrophobic amino and epoxy monomers provided hydrophobic interaction sites. Due to the synergistic effect of hydrophobic interaction and B-N coordination, the PBAPM exhibited excellent binding amounts for nitrogen-containing sulfonamides (SAs). In addition, the PBAPM possessed excellent stability, rigidity and permeability. Therefore, the PBAPM was used as solid phase microextraction (SPME) material for enrichment and separation of SAs from aqueous samples. The PBAPM SPME was optimized in detail, and combined with ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) analysis for simultaneous determination of 10 kinds of SAs from tap, lake and river water. Using only 1 mL of water samples, limit of quantitation of SAs could reach 0.54-4.5 ng L-1. Recoveries of standard spiked SAs from water samples were between 82.0% and 105.4%, with intra-day and inter-day relative standard deviation ranging from 3.3% to 5.6% and 4.2% to 8.1%, respectively. The PBAPM SPME combined with UPLC-MS/MS method shown better or similar recoveries, and used fewer samples than previous methods. These results demonstrated that the PBAPM could selectively separate and enrich ultra-trace nitrogen-containing SAs from aqueous samples.

Synthesis of boronate-decorated polyethyleneimine-grafted porous layer open tubular capillaries for enrichment of polyphenols in fruit juices.

A combination between modification with porous layer and grafting of polyethyleneimine (PEI) on the inner face of capillary was for the first time developed for boronate affinity in-tube solid-phase microextraction (SPME) material to enhance the extraction capacity for cis-diol-containing polyphenols. The successful synthesis of boronate-decorated polyethyleneimine-grafted porous layer open tubular (BPPLOT) capillary was confirmed by scanning electron micrograph, Fourier transform-infrared spectra and absorption experiments. The porous layer, PEI and boronate affinity provided high specific surface area, more binding sites for boronate groups and specific selectivity of BPPLOT capillary, respectively. The maximum binding quantity of BPPLOT capillary greatly improved, and ranged from 143 to 170 µg m-1 for cis-diol-containing polyphenols (catechin, chlorogenic acid, caffeic acid and epicatechin). A green method based on boronate affinity in-tube SPME was developed for separation and enrichment polyphenols, and some parameters of in-tube SPME were optimized. After in-tube SPME, HPLC with UV detection was used for quantitative determination of polyphenols. Recoveries of standard spiked cis-diol-containing polyphenols from fruit juice were between 80.9% and 102%, with intra-day and inter-day coefficient of variation ranging from 4.8% to 7.3% and 5.0% to 8.6%, respectively. Conversely, recovery of non-cis-diol-containing ferulic acid was no greater than 3.0%. These results suggested that the BPPLOT capillary could effectively separate and enrich cis-diol-containing polyphenols from real samples.