Porous carbon derived from a metal-organic framework as an efficient adsorbent for the solid-phase extraction of phthalate esters

Migration and distribution characteristics of typical organic pollutants in condensable particulate matter of coal-fired flue gas and by-products of wet flue gas desulfurization system

The wet flue gas desulfurization (WFGD) system of coal-fired power plants shows a good removal effect on condensable particulate matter (CPM), reducing the dust removal pressure for the downstream flue gas purification devices. In this work, the removal effect of a WFGD system on CPM and its organic pollutants from a coal-fired power plant was studied. By analyzing the organic components of the by-products emitted from the desulfurization tower, the migration characteristics of organic pollutants in gas, liquid, and solid phases, as well as the impact of desulfurization towers on organic pollutants in CPM, were discussed. Results show that more CPM in the flue gas was generated by coal-fired units at ultra-low load, and the WFGD system had a removal efficiency nearly 8% higher than that at full load. The WFGD system had significant removal effect on two typical esters, especially phthalate esters (PAEs), with the highest removal efficiency of 49.56%. In addition, the WFGD system was better at removing these two esters when the unit was operating at full load. However, it had a negative effect on n-alkanes, which increased the concentration of n-alkanes by 8.91 to 19.72%. Furthermore, it is concluded that the concentration distribution of the same type of organic pollutants in desulfurization wastewater was similar to that in desulfurization slurry, but quite different from that in coal-fired flue gas. The exchange of three organic pollutants between flue gas and desulfurization slurry was not significant, while the concentration distribution of organic matters in gypsum was affected by coal-fired flue gas.

Application of an MOF-based dispersive micro solid phase extraction method followed by dispersive liquid–liquid microextraction for plasticizers’ detection and determination

In this research, MIL-68 (Al) was synthesized and used for the extraction of some plasticizers from various samples stored in plastic bottles.

Surface modification of coconut shell activated carbon for efficient solid-phase extraction of N-nitrosodimethylamine from water

A practical and cheap methodology in modifying commercial coconut shell activated carbon for solid-phase extraction of N-nitrosodimethylamine in water was developed through an understanding of activated carbon surface chemistry. In comparison with commercial activated carbon, extraction recoveries by activated carbon treated with sulfuric acid decreased by 50%, while those of activated carbon heated at 800°C improved by more than 100%. Acid treatment increased the oxygen content on the carbon's surface. In contrast, heat treatment decreased the surface oxygen content, resulting in a more hydrophobic surface, which favoured adsorption and extraction of N-nitrosodimethylamine. The influence of different activated carbon sizes, amount of modified activated carbon, and pH on the N-nitrosodimethylamine recoveries was assessed and compared with the commercial solid-phase extraction cartridge. The recommended amount of powder activated carbon treated at 800°C was 3 g to yield an optimum recovery of 130%, which was superior to the commercial solid-phase extraction cartridges. The method validation results confirmed the high accuracy, reproducibility, and precision of the method. The study indicated that chemisorption plays a significant role in the adsorption of N-nitrosodimethylamine on activated carbon, and the optimization of its surface chemistry can enhance N-nitrosodimethylamine adsorption/extraction from water.

Rapid Determination of 17 Phthalate Esters in Capsanthin by QuEChERS Coupled with Gas Chromatography-Mass Spectrometry

A method for the simultaneous determination of 17 kinds of phthalate esters in capsanthin was developed by the QuEChERS (quick, easy, cheap, effective, ruggedand safe) pretreatment method coupled with gas chromatography-mass spectrometry(GC-MS). Capsanthin samples were extracted with acetonitrile, and then sodium chloride and anhydrous magnesium sulfate were added for salting out. After the extracting liquids were cleansed by florisil, the supernatants were analyzed by GC-MS. The limits of detection (LOD) and limits of quantitation (LOQ) ranged from 0.2 to 0.5 μg/g and 0.6 to 1.5 μg/g, respectively. DMP, DEP, DAP, DIBP, DBP, BMPP, DPP, DHXP and DCHP were in the range of 0.2 - 10 μg/g; DMEP, DEEP, BBP, DBEP, DEHP, DPhP, DNOP and DNP were in the range of 0.5 - 20 μg/g. And all had good linearity and the linear correlation coefficients (R²) were more than 0.995. The average recoveries of 17 kinds of PAEs of the three levels were between 82.8 and 118.1%, and the relative standard deviations (RSDs) were between 0.12 and 7.3%. It is a simple, rapid, accurate and reliable method for the rapid detection of PAEs in large quantities of natural plant extract samples.

Zirconium metal-organic framework assisted miniaturized solid phase extraction of phenylurea herbicides in natural products by ultra-high-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry

The zirconium metal-organic framework (Zr-MOF) was used as a novel and effective adsorbent material for the enrichment of five phenylurea herbicides (fenuron, monuron, diuron, linuron and pencycuron) in natural products. The target analytes were determined by ultra-high-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry. Some crucial experimental parameters, such as type of adsorbents, amount of adsorbent, type of eluent solvents and adsorption capacity were investigated and optimized. Under the optimum extraction conditions, the enrichment factors of fenuron, monuron, diuron, linuron and pencycuron were 90, 128, 148, 204 and 295 times, respectively. A good linearity was obtained in different concentration levels of target analytes with the determination coefficients (r²) larger than 0.993. In addition, the limits of detection varied from 0.05 to 0.36 ng/mL and the recoveries of the analytes were in the range of 85.19-99.13 %. The results demonstrated that the proposed miniaturized solid-phase extraction procedure coupled with Zr-MOF could become an effective tool to analyze phenylurea herbicides and would have the vast application prospect for the extraction of pesticide residue and more organic pollutants from Hawthorn, Dendrobii Officinalis Caulis and Salviae Miltiorrhizae Radix et Rhizoma samples.

Recent advances in metal-organic frameworks and covalent organic frameworks for sample preparation and chromatographic analysis

In the field of analytical chemistry, sample preparation and chromatographic separation are two core procedures. The means by which to improve the sensitivity, selectivity and detection limit of a method have become a topic of great interest. Recently, porous organic frameworks, such as metal-organic frameworks (MOFs) and covalent organic frameworks (COFs), have been widely used in this research area because of their special features, and different methods have been developed. This review summarizes the applications of MOFs and COFs in sample preparation and chromatographic stationary phases. The MOF- or COF-based solid-phase extraction (SPE), solid-phase microextraction (SPME), gas chromatography (GC), high-performance liquid chromatography (HPLC) and capillary electrochromatography (CEC) methods are described. The excellent properties of MOFs and COFs have resulted in intense interest in exploring their performance and mechanisms for sample preparation and chromatographic separation.

Recent applications of metal-organic frameworks in sample pretreatment

Metal-organic frameworks are promising materials in diverse analytical applications especially in sample pretreatment by virtue of their diverse structure topology, tunable pore size, permanent nanoscale porosity, high surface area, and good thermostability. According to hydrostability, metal-organic frameworks are divided into moisture-sensitive and water-stable types. In the actual applications, both kinds of metal-organic frameworks are usually engineered into hybrid composites containing magnetite, silicon dioxide, graphene, or directly carbonized to metal-organic frameworks derived carbon. These metal-organic frameworks based materials show good extraction performance to environmental pollutants. This review provides a critical overview of the applications of metal-organic frameworks and their composites in sample pretreatment modes, that is, solid-phase extraction, magnetic solid-phase extraction, micro-solid-phase extraction, solid-phase microextraction, and stir bar solid extraction.