Diethoxy-pillar[5]arenes doped poly(deep eutectic solvent-co-ethylene glycol dimethacrylate) monolithic column: An efficient sorbent for pipette tip micro solid-phase extraction and sensitive determination of eight phthalate esters in baijiu

In this study, a diethoxy-pillar[5] arene (EtP5) doped deep eutectic solvent (DES) monolithic column was prepared using diethylene glycol dimethacrylate (EGDMA) as the crosslinker for pipette tip micro-solid phase extraction (PT-μSPE) of phthalate esters (PAEs). The column was characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, nitrogen adsorption-desorption measurement, thermogravimetric analysis, and contact angle goniometry. The saturated adsorption capacities of the EtP5 doped poly(DES- co -EGDMA) monolithic column for dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), butyl benzyl phthalate (BBP), dicyclohexyl phthalate (DCHP), diethylhexyl phthalate (DEHP), dioctyl phthalate (DOP), and dinonyl phthalate (DNP) were 15.3, 22.7, 41.2, 43.0, 37.6, 36.1, 35.6, and 32.8 mg·g −1 , respectively. The EtP5 doped poly(DES- co -EGDMA) monolithic column has a service life of at least 80 cycles and exhibits superior adsorption selectivity for PAEs. Electrostatic potential analysis, Fourier transform infrared analysis and the relationship between the adsorption capacity and hydrophobic coefficients (log K ow ) of PAEs indicated the existence of C − H⋯π interaction, π-π stacking and hydrophobic interaction between PAEs and EtP5, as well as O − H⋯O hydrogen bond interaction between PAEs and ChCl-IA. After optimizing the extraction conditions, a PT-μSPE-HPLC-UV method was established for the detection of 8 PAEs in baijiu. The method exhibited linear ranges of 0.5–1000 μg·L −1 for DMP and DEP; 1.0–1000 μg·L −1 for DBP, BBP, and DCHP; 1.5–1000 μg·L −1 for DEHP and DOP; and 2.0–1000 μg·L −1 for DNP (R 2  ≥ 0.998). The limits of detection (LODs, S/N = 3) and limits of quantitation (LOQs, S/ N  = 10) ranged from 0.2 to 0.7 μg·L −1 and 0.5 to 2.0 μg·L −1 , respectively. Recoveries of the 8 PAEs in spiked baijiu samples ranged from 83.7 % to 105.5 %. Intra-day and inter-day precisions (RSDs) were no more than 6.0 %. These results demonstrate that the EtP5 doped poly(DES- co -EGDMA) monolithic column is an ideal medium for the separation and detection of PAEs in baijiu.