Ionic liquids (ILs) have presented excellent behaviors in the separation of azeotropes in extractive distillation. However, the intrinsic molecular nature of ILs in the separation of azeotropic systems is not clear. In this paper, Fourier-transform infrared spectroscopy (FTIR) and theoretical calculations were applied to screen the microstructures of ethyl propionate–n-propanol–1-ethyl-3-methylimidzolium acetate ([EMIM][OAC]) systems before and after azeotropy breaking. A detailed vibrational analysis was carried out on the v(C=O) region of ethyl propionate and v(O–D) region of n-propanol-d1. Different species, including multiple sizes of propanol and ethyl propionate self-aggregators, ethyl propionate–n-propanol interaction complexes, and different IL–n-propanol interaction complexes, were identified using excess spectroscopy and confirmed with theoretical calculations. Their changes in relative amounts were also observed. The hydrogen bond between n-propanol and ethyl propionate/[EMIM][OAC] was detected, and the interaction properties were also revealed. Overall, the intrinsic molecular nature of the azeotropy breaking was clear. First, the interactions between [EMIM][OAC] and n-propanol were stronger than those between [EMIM][OAC] and ethyl propionate, which influenced the relative volatilities of the two components in the system. Second, the interactions between n-propanol and [EMIM][OAC] were stronger than those between n-propanol and ethyl propionate. Hence, adding [EMIM][OAC] could break apart the ethyl propionate–n-propanol complex (causing the azeotropy in the studied system). When x([EMIM][OAC]) was lower than 0.04, the azeotropy still existed mainly because the low IL could not destroy the whole ethyl propionate–n-propanol interaction complex. At x(IL) > 0.04, the whole ethyl propionate–n-propanol complex was destroyed, and the azeotropy disappeared.
Triazine herbicides are a category of key and broad-spectrum herbicides in agricultural crops. However, their unintended and excessive use has caused irreparable damage to environmental and agro-food safety concerns, thus harming human health. Herein, we report on a new hydroxylated microporous organic network (OH−MON) with a permanent micropore of 1.72 nm, high surface area, and high stability, synthesized by simple Sonogashira–Hagihara polymerization. When utilized as an advanced solid-phase extraction adsorbent for efficient adsorption of triazine herbicides, this established analytical approach showed an ultra-low detection limit (0.03−0.15 ng∙L -1 ), and a satisfactory reproducibility attributable to the generated rich selective hydrogen-bonding groups on the highly accessible inner skeleton, as demonstrated by the theoretical calculation and selectivity test. This study suggested the enormous practical application potential of OH−MON for preconcentration and detection of triazine herbicides in a complex matrix.
The paper reviews applications of calixarenes in capillary electrophoresis,mainly including calixarenes as buffer additives and prepartion materials of capillary coating in capillary electrophoresis.;
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