Revolution teaching practice in sample pretreatment supported by large-scale instrument： a case study of magnetic covalent organic framework enriching organic ultraviolet filters in seawater

doi:10.3724/SP.J.1123.2025.08010

Abstract

Abstract:

Current undergraduate environmental chemistry curricula often suffer from a disconnect between sample preparation and large-scale instrumental analysis， making it difficult to cultivate students’ systematic analytical capabilities. Furthermore， the experimental content predominantly focuses on conventional water quality parameters and traditional pollutants like heavy metals， lacking training in monitoring and remediation technologies for new pollutants， which creates a significant gap with national strategic needs. To address this issue， this study designed an integrated comprehensive experiment that combines material synthesis， sample pretreatment， and large-scale instrumental analysis， targeting typical new pollutants， such as organic ultraviolet filters （OUVFs） from pharmaceuticals and personal care products. A magnetic covalent organic framework （MCOF） was synthesized via a reflux heating method. Students were guided to apply it as the sorbent in magnetic solid-phase extraction （MSPE）. Owing to its facile magnetic separation， the rapid enrichment of OUVFs was achieved within 8 min， followed by quantitative determination of seawater samples using ultra-high performance liquid chromatography-tandem mass spectrometry （UHPLC-MS/MS）. Through a three-stage teaching module encompassing “pre-class preview， in-class experiment， and post-class discussion”， the experiment emphasizes enhancing students’ independent exploration abilities in adsorbent synthesis and characterization， optimization of enrichment parameters， and data analysis. Teaching practice has shown that this design not only enabled students to deeply understand the complex sample pretreatment process and the mechanism of multi-factor synergistic effects， but also significantly enhanced their comprehensive innovation and practical abilities in solving new pollutant monitoring problems.

Key words: integrated chemistry experiment, liquid chromatography-tandem mass spectrometry （LC-MS/MS）, magnetic solid-phase extraction （MSPE）, teaching reform, environmental chemistry

CLC Number:

O658

LI Shuang, ZHU Yiling, REN Zhen, GAO Dangdang, GU Helin, LAO Junlang. Revolution teaching practice in sample pretreatment supported by large-scale instrument： a case study of magnetic covalent organic framework enriching organic ultraviolet filters in seawater[J]. Chinese Journal of Chromatography, 2026, 44(6): 705-712.

Figures/Tables 8

Fig. 1 Structural formulas of the four organic ultraviolet filters （OUVFs）OC： octocrylene； OMC： octyl methoxycinnamate； EHS： ethylhexyl salicylate； AVO： avobenzone.

Fig. 2 Synthesis process of Fe3O4@TFPB-BDBD： benzidine； THF： tetrahydrofuran； TFPB： 4-［3，5-bis（4-formylphenyl）phenyl］ben-zaldehyde； COF： covalent organic framework； MCOF： magnetic covalent organic framework.

Fig. 3 Procedure of magnetic solid phase extraction

Table 1 Physicochemical properties and MS parameters of the four OUVFs

Analyte	M_r	pK_a	lg K_ow	t_R/min	Precursor ion （m/z）	Product ions （m/z）	Declustering potentials/V	Collision energies/eV
OC	361.5	7.5	6.4	8.7	362.1	250.1^*， 231.9	45.4， 50.0	12.0， 29.0
OMC	290.4	7.5	5.0	9.0	291.3	179.0^*， 161.0	45.8， 36.5	12.9， 26.4
EHS	250.3	8.1	4.4	9.2	251.1	120.9^*， 138.9	33.3， 36.5	33.7， 12.6
AVO	310.4	9.7	4.3	8.9	311.0	161.0^*， 135.1	52.9， 55.9	35.0， 30.7

Fig. 4 （a） Microstructural image and （b） FT-IR spectra of Fe3O4@TFPB-BD

Fig. 5 Effects of （a） dosage of Fe3O4@TFPB-BD，（b） pH of water sample，（c） adsorption time and （d） type of eluent on the enrichment efficienciesACN： acetonitrile； MeOH： methanol； FA： formic acid； TFA： trifluoroacetic acid.

Table 2 Performance parameters of the analytical method for the four OUVFs

OUVF	Regression equation	Correlation coefficient	Linear range/（ng/L）	LOD/（ng/L）	LOQ/（ng/L）	RSD/%
OC	y=109.95x+1579.61	0.9955	2‒2000	0.38	1.24	7.89‒14.87
AVO	y=320.00x+67294.86	0.9998	2‒2000	0.29	0.94	9.15‒14.53
OMC	y=170.44x‒1876.29	0.9905	2‒2000	0.23	0.77	0.97‒12.44
EHS	y=11.65x+166.83	0.9973	2‒2000	0.34	1.13	9.48‒14.89

Fig. 6 Chromatograms of the four OUVFs in （a） a real seawater sample and （b） a spiked seawater sample （2?000 ng/L）

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