Significant Progress on the Development of Covalent Organic Frameworks-Based Solid-Phase Microextraction Probe
Rapid, sensitive, and accurate analysis of trace environmental pollutants is urgently required in the field of environmental analytical chemistry. Per- and polyfluoroalkyl substances (PFASs) are a series of persistent organic pollutants (POPs) widespread in environment and organism, and they have been concerned widely by both health authorities and public due to their hepatotoxicity, reproductive toxicity, and potential carcinogenicity. Perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) are the two most widely used PFASs that have been designated as target chemicals for regulation by the Stockholm Convention on POPs. It is necessary to monitor the contents and compositions of PFASs in environmental and biological media for understanding their environmental behaviors and toxic effects.
Mass spectrometry (MS) has always been the preferred method for determination of trace analytes in complex samples. However, PFASs exist in environmental and biological media with very low concentrations. This, together with the complicated sample matrices and limited samples for analysis make the conventional MS-based methods become cumbersome, labor-intensive, and time-consuming. The development of ambient ionization techniques in the early 21st century offers MS the opportunity for rapid analysis of complex samples under ambient and open-air conditions with minor or no sample pretreatment. Coupling solid-phase microextraction (SPME) with ambient MS has been considered as an effective approach to achieve rapid, direct, and sensitive analysis of trace analytes in complex samples.
Herein, a novel covalent organic frameworks (COFs)-based SPME probe was developed by the group of Prof. Yunyun Yang from Institute of Analysis, Guangdong Academy of Sciences, and the COFs-SPME has been coupled with nanoelectrospray ionization (nanoESI)-MS under ambient and open-air conditions to achieved rapid, sensitive, and accurate analysis of trace PFASs in complex environmental and biological media. The COFs sorbent with highly selective enrichment toward PFASs was designed, and a facile synthesis method was developed to achieve high product yield and high crystallinity. The COFs was synthesized by condensation of 2,3,5,6-tetrafluorotelephtal aldehyde and 2,4,6-tris(4-aminophenyl)-1,3,5-triazine via imine bonds, which showed strong adsorption towards PFASs via pore size selection, hydrophobic interactions, fluorine-fluorine interactions, electrostatic interactions together with hydrogen bond interactions. A novel biocompatible COFs-SPME probe with high selectivity and enrichment capacity toward PFASs was prepared, which can be used for direct sampling and extraction of PFASs from complex environmental and biological media. After extraction, the loaded COFs-SPME probe was directly applied to nanoESI-MS analysis under ambient and open-air conditions (Fig. 1). By using the proposed method, rapid, sensitive, and accurate detection of PFASs in environmental water and whole blood has been successfully achieved. This research provides new possibilities for rapid analysis and monitoring of trace environmental pollutants in complex matrices, which is of great scientific value and application prospects.
Figure 1. Schematic diagram for analysis of PFASs by COFs-SPME coupled with nanoESI-MS.
This work "Covalent organic frameworks-based solid-phase microextraction probe for rapid and ultrasensitive analysis of trace per- and polyfluoroalkyl substances using mass spectrometry" has been published in Analytical Chemistry (Top first ranking journal of the Chinese Academy of Sciences). The first author was Dr. Yajun Hou, and the corresponding author was Prof. Yunyun Yang. Link of the article: https://pubs.acs.org/doi/abs/10.1021/acs.analchem.0c01829.