Nitrogen-rich covalent organic frameworks as solid-phase extraction adsorbents for separation and enrichment of four disinfection by-products in drinking water.

Disinfection by-products (DBPs) in drinking water can pose a health risk to humans. In this work, a new nitrogen-rich covalent organic frameworks (TpTt-COFs) was synthesized and applied firstly as a novel solid-phase extraction (SPE) trapping media for four ultra-trace levels of DBPs in drinking water samples. Under the optimal conditions, these DBPs were absorbed on a SPE cartridge; then, the DBPs were eluted with the optimized volume of eluent. The concentrated elution was detected and quantified by gas chromatography-mass spectrometry. Low limits of detection (0.0004-0.0063 ng mL-1), wide linearity (0.002-50 µg L-1), good reproducibility (1.54-2.88%) and repeatability (1.28-3.40%) were obtained. This novel method has been successfully applied to the analysis of ultra-trace levels DBPs in real drinking water samples. These accurate experimental results by this method indicated that the novel TpTt-COFs as a SPE trapping material was an attractive option for efficient and effective analysis of ultra-trace levels DBPs in future.

Amino-modified covalent organic framework as solid phase extraction absorbent for determination of carboxylic acid pesticides in environmental water samples.

The amino-modified covalent organic framework (NH2@COF) was synthesized via the thiol-ene click reaction of vinyl covalent organic framework (COF) with 4-aminobenzenethiol. The introduction of amino groups can interact with the anionic headgroup of carboxylic acid pesticides. Moreover, ample hydrophilic surface area can boost absorption in the water media. The NH2@COF was fully characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. Compared with vinyl COF and four commercial absorbents, the NH2@COF shows higher extraction efficiency for carboxylic acid pesticides. The solid phase extraction (SPE) conditions, involving flow rate, ionic strength, sample pH, desorption solvent, and desorption solvent volume, were optimized in details. Under the optimized conditions, the NH2@COF was successfully applied for the enrichment and determination of six carboxylic acid pesticides in environmental water samples combined with high performance liquid chromatography. The method features wide linearity (0.2-100 ng mL-1, r > 0.999), low limits of quantification (0.04-0.20 ng mL-1), and excellent precision (RSDs ≤ 8.7%). The recoveries range from 89.6% to 102.4% with RSDs ≤ 7.1%. Therefore, the NH2@COF-SPE method is an efficient pretreatment procedure and can be utilized for the selective extraction of carboxylic acid pesticides from environmental water samples.

A water-compatible magnetic molecularly imprinted polymer for the selective extraction of risperidone and 9-hydroxyrisperidone from human urine.

An accurate, rapid, and sensitive method for the determination of risperidone and 9-hydroxyrisperidone in urine samples was developed by combining water-compatible magnetic molecularly imprinted solid-phase extraction with high performance liquid chromatography. Several variables relating to the efficiency of magnetic solid phase extraction were optimized, including the amount of adsorbent, adsorption time, type of elution solvent, and desorption time. The analytical performance of this method was validated under the optimized conditions. The linearity for risperidone and 9-hydroxyrisperidone was obtained in the range 1-2000ngmL-1 with correlation coefficient ≥ 0.991. Limits of detection of risperidone and 9-hydroxyrisperidone are 0.21ngmL-1 and 0.24ngmL-1, respectively. Recoveries at three spike levels (10, 100, and 1000ngmL-1) ranged from 94.6% to 102.4% with relative standard deviations (%) ≤ 5.3. These results confirmed that this method can be successfully and facilely used to analyze the multi-residues of risperidone and 9-hydroxyrisperidone in urine samples with high efficiency and good sensitivity.

One-pot synthesis of substituted furans using Cu(OTf)(2)-catalyzed propargylation/cycloisomerization tandem reaction.

A convenient one-pot propargylation/cycloisomerization tandem process has been developed for the synthesis of substituted furans derivatives from 1,3-dicarbonyl compounds and enoxysilanes with propargylic alcohols or acetates using copper(II) triflate as a bifunctional catalyst. This method provides a flexible and rapid route to substituted furans.