Microporous hydrogen-bond organic frameworks-based SALDI-TOF MS for simultaneous enrichment and high sensitivity detection of paraquat and chlormequat

Abstract

This study proposes a surface-assisted laser desorption ionization time-of-flight mass spectrometry (SALDI-TOF MS) method using an ultrastable microporous hydrogen-bonded organic frameworks (MP-HOFs) for selective and sensitive analysis of two common organic pesticides: paraquat (PQ) and chlormequat (CQ) in real samples. MP-HOFs are formed by H-bonding self-assembly of co-planar π-conjugated large aromatic tectons with carboxylate groups. They can not only efficiently absorb and transfer laser energy, but also specifically capture and isolate target analytes from complicated systems. The proposed SALDI-TOF MS method exhibited high salt tolerance and low background. The selective enrichment performance of MP-HOFs was demonstrated by analyzing PQ and CQ in real samples. Simultaneous analysis results of PQ and CQ showed satisfactory reproducibility with relative standard deviations (RSDs) of 3.2–9.2% and 5.7–12.3% for spot-to-spot and sample-to-sample, good linearity (R2 > 0.99), and high sensitivity with a limit of detection of 0.001 and 0.05 ng mL−1, respectively. The detection limits of PQ and CQ test analytes were three and two orders of magnitude lower than those of non-enriched PQ and CQ, respectively. Furthermore, the possible ionization mechanism was discussed, and the presented approach was successfully applied for PQ and CQ detection in tap water, river water, and soil, confirming its potential in practical applications.