Sensitive monitoring of trace nitrophenols in water samples using multiple monolithic fiber solid phase microextraction and liquid chromatographic analysis

• A new porous monolith-based sorbent was prepared.
• The sorbent was used as extraction medium of MMF-SPME.
• The new sorbent could extract nitrophenols effectively with multiple interactions.
• Method of sensitive monitoring of trace nitrophenols in water samples was developed.

In this work, a simple, efficient and environmentally friendly method—multiple monolithic fiber solid-phase microextraction (MMF-SPME) combining with high-performance liquid chromatography (HPLC) was first established for the determination of six trace nitrophenols in water samples. In order to prepare MMF-SPME, 1-allyl-3-methylimidazolium bis [(trifluoro methyl) sulfonyl] imide was co-polymerized with ethylene dimethacrylate to get single thin fiber (0.5 mm in diameter). Subsequently, four thin fibers were bound together to obtain the MMF-SPME. The effect of preparation conditions of MMF-SPME on the extraction performance was investigated in detail. In order to obtain the optimal extraction conditions of MMF-SPME for nitrophenols, several extractive parameters, including desorption solvent, extraction and desorption time, pH values and ionic strength in sample matrix were optimized. Under the optimum conditions, the linear ranges of 4-nitrophenol, 2,4-dinitrophenol, 5-methyl-2-nitrophenol, 5-methoxyl-2-nitrophenol were 0.5–200 µg/L and 1.0–200 µg/L for 2-nitrophenol and 4-tertbutyl-2-nitrophenol. The limits of detection (S/N=3) for the target analytes were 0.075–0.27 µg/L. At the same time, excellent method reproducibility was achieved in terms of intra- and inter-day precisions, indicated by the RSDs of both <10.0%, respectively. Finally, the proposed method was successfully used to detect nitrophenols in different environmental water samples. Satisfactory recoveries ranged from 82.6% to 116% and the RSDs for reproducibility were less than 10% for target analytes in all real samples.

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