Sulfonic acid functionalized hierarchical porous covalent organic frameworks as a SALDI-TOF MS matrix for effective extraction and detection of paraquat and diquat

• Published in: Journal of colloid and interface science 2021-12, Vol.603, p.172-181
• Main Authors: Tan, Wei, Xu, Xianyan, Lv, Yuanxia, Lei, Wenjuan, Hu, Kun, Ye, Fanggui, Zhao, Shulin
• Format: Article
• Language: English
• Subjects: DFT calculation; Food samples; Quaternary ammonium herbicides; SALDI-TOF MS; Sulfonic acid functionalized hierarchical porous COFs
• ISSN: 0021-9797; 1095-7103
• DOI: 10.1016/j.jcis.2021.06.077

Sulfonic acid functionalized hierarchical porous covalent organic frameworks (H-COF-SO3H) synthesized by defect-structure and post-synthesis modification method could be used as adsorbent and matrix for detecting quaternary ammonium herbicides paraquat and diquat in food samples by surface-assisted laser desorption/ionization time-of-flight mass spectrometry (SALDI-TOF MS). [Display omitted] •-SO3H functionalized hierarchical porous COFs prepared by defect-structure and post-synthesis modification.•Mass spectra of PQ and DQ with H-COF-SO3H as SALDI-TOF MS matrix had interference-free background.•-SO3H modification endowed H-COF-SO3H with high and selective enrichment to quaternary ammonium herbicides PQ and DQ.•Adsorption mechanism between analytes and adsorbents were investigated by DFT calculation.•Trace PQ and DQ in food samples could be detected by SALDI-TOF MS with H-COF-SO3H as adsorbent and matrix. Design and construction of a matrix with specific adsorption on the target compounds can effectively reduce the detection limit of surface-assisted laser desorption/ionization time-of-flight mass spectrometry (SALDI-TOF MS) analysis. Sulfonic acid functionalized hierarchical porous covalent organic frameworks (H-COF-SO3H) was synthesized by defect-structure and post-modification method, and then used as matrix and adsorbent for the determination of quaternary ammonium herbicides paraquat (PQ) and diquat (DQ). N2 adsorption–desorption experiments confirmed that H-COF-SO3H possesses hierarchical porosity with pore widths concentrated at 1.3,1.5, and 2.8 nm. The strong UV absorption at 200–450 nm and good thermal stability made H-COF-SO3H being a promising matrix without background interference. H-COF-SO3H can efficiently enrich PQ and DQ via electrostatic attraction, and the key role of -SO3H group on specific adsorption was confirmed by density functional theory (DFT) calculations. The limits of detection (LODs) for PQ and DQ with H-COF-SO3H enrichment were 0.5 and 0.1 ng·mL−1, respectively, which were 20 and 60 times higher than those without H-COF-SO3H enrichment, respectively. The spiked recoveries of PQ and DQ for the three food samples were 92.0–113.2% and 80.1–102.6% with RSDs of 2.2–9.2% and 2.0–8.7%, respectively. This work provides an analyte-oriented approach for fabricating SALDI-TOF MS matrix.