Highly hydrophobic calixarene polymers for efficient enrichment of polar nitrobenzene compounds

Macrocyclic polymer materials exhibit excellent selectivity and adsorption performance in pollutant adsorption due to unique host-guest recognition. Herein, three kinds of calixarene polymers (C4P, C6P and C8P) were synthesized through Sonogashira reaction, and were characterized through ¹H NMR, FT-IR, SEM, and TEM. The water contact angle experiments revealed that three kinds of calixarene polymers were highly hydrophobic, and they all exhibited high enrichment efficiency for weak polar chloro-substituted benzene compounds (chlorobenzene, o-chlorotoluene, p-dichlorobenzene and o-dichlorobenzene) and BTEX (benzene, toluene, ethylbenzene and xylenes). Surprisingly, three types of calixarene polymers also showed satisfactory enrichment performance for polar nitrobenzene compounds (NBCs). Among them, C8P showed the most outstanding enrichment factors for NBCs (825-1913), which was about 2-7 times better than those of the commercial fibers. Using C8P as coating fiber, a sensitive analytical method was further developed based on solid phase microextraction (SPME), coupled with gas chromatography-mass spectrometry (GC-MS). The established analytical method demonstrated low detection limits (0.06-5.08 ng L^-1), a wide linear range (0.5-1000 ng L^-1), and good repeatability. The established method was further applied to the quantification of NBCs in environmental water samples, verifying its feasibility.