Vortex-assisted solid-phase extraction based on metal-organic framework/chitosan-functionalized hydrophilic sponge column for determination of triazine herbicides in environmental water by liquid chromatography-tandem mass spectrometry.

In the presented work, MIL-101(Cr) and chitosan were directly embedded on the skeleton of melamine sponge material using a simple and environmentally friendly method. Chitosan acts not only as an adhesive during the preparation of functionalized sponges, but also as an adsorption adjuvant in herbicide detection. Unlike other polymers, chitosan has excellent hydrophilicity and contains numerous adsorption sites; thus, it enables the sponge material to be used for determination of contaminants in an aqueous phase. Scanning electron microscopic (SEM) analysis showed that the coating material was uniformly distributed on the skeleton of melamine sponge. The prepared material was used as a sorbent in a vortex-assisted solid-phase extraction and combined with high performance liquid phase tandem mass spectrometry for the extraction and trace determination of six triazines in water samples (Atraton, Desmetryn, Prometon, Ametryn, Prometryn and Dimethametryn). Several parameters that affect the extraction efficiencies were investigated. Under the optimal conditions (MIL-101(Cr) loading, 150 mg; sample pH, 7; salt concentration, 0%; adsorption time, 3 min; desorption solvent, 1.5 mL acetonitrile; desorption time, 4 min), the proposed method was successfully used in the determination of trace triazines in five real water samples (drinking water, tap water, lake waters and river water), satisfactory recoveries were obtained in the range of 78.9%-118.6%. The limits of detection of the proposed method in detecting triazine herbicides in spiked water samples ranged from 0.014 to 0.045 ng mL-1.

A semi-automatic solid phase extraction system based on MIL-101(Cr) foam-filled syringe for detection of triazines in vegetable oils.

In this study, several metal-organic framework-melamine foam columns were first developed and used as a laboratory-made semi-automatic solid phase extraction packed in syringe adsorber for the extraction of six triazine herbicides from vegetable oil samples coupled to high-performance liquid chromatography-tandem mass spectrometry. The metal-organic framework-foam columns were prepared using a simple approach by embedding the solid particles in melamine foam using polyvinylidene difluoride physical encapsulation. The method was applicable to a wide variety of metal-organic framework materials, and the incorporated materials retained their unique properties. Key factors that affect the extraction efficiency, including the MIL-101(Cr) amount, sample flow rate, type and volume of the eluting solvent, and flow rate of eluting solvent, were investigated. Under optimum conditions, the proposed method exhibited low limits of detection (0.017-0.096 ng/mL, S/N = 3) for six triazines. The relative standard deviations calculated for all herbicides ranged from 0.2 to 14.9%. This study demonstrated that the MIL-101(Cr)-foam column can be used as a high-quality adsorption material for the detection of triazines in vegetable oils.

Application of an in-situ formulated magnetic deep eutectic solvent for the determination of triazine herbicides in rice.

In this work, a rapid, convenient, sensitive, and cost-effective in-situ formed magnetic deep eutectic solvent based on a dispersive liquid-liquid extraction method was developed for the determination of triazine herbicides in rice. A novel tetrabutylammonium chloride (TBAC) based magnetic deep eutectic solvent (MDES), [TBAC/ethylene glycol][FeCl4] was generated by means of an simple in-situ reaction of the deep eutectic solvent (DES) with iron chloride in the sample solution. The solvent which has high affinity for target analytes and magnetic ability was successfully employed as an extraction solvent and simplified both the extraction and separation procedure. A series of parameters influencing the extraction efficiency were investigated. Under optimal conditions, calibration curves for the target triazine herbicides were obtained in the ranges of 5-1000 ng g-1, with correlation coefficients greater than 0.9910. The limits of detection (LOD) and quantification (LOQ) were in the range of 1.49-3.10 ng g-1 and 4.96-10.34 ng g-1, respectively. The precision of intra- and inter-day were under 6.2% and 9.6%, respectively, and the precision between laboratories were lower than 7.5%. The accuracy of the method varied from 84.9 to 117.5%. Furthermore, the method showed satisfactory matrix effect and robustness. These results indicate that the technique is suitable for rice sample analysis.

MIL-101(Cr)/MWCNTs-functionalized melamine sponges for solid-phase extraction of triazines from corn samples, and their subsequent determination by HPLC-MS/MS.

In the presented work, we proposed the use of polyvinylidene difluoride (PVDF) as a coupling agent to load MIL-101(Cr) and carboxylated multi-walled carbon nanotubes (MWCNTs) on the skeleton of melamine sponge (MeS) for the preparation of novel extraction media with high-efficiency. The morphology and structure of this composite were characterized by scanning electron microscopy (SEM) analyses. The obtained MIL-101(Cr)/MWCNTs functionalized MeS(MIL/M-MeS) cube was used as a sorbent for the solid-phase extraction (SPE) of six triazines (Atraton, Simetryne, Prometon, Ametryn, Propazine, and Prometryn) spiked corn samples. Several parameters that may affect the extraction efficiencies, including type and volume of extraction solvent, times of ultrasonic extraction, adsorption, and desorption; type and volume of desorption solvent, were optimized. This was followed by elution containing the herbicides, which were quantified using high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). Under optimum conditions, the analytical method for the preparation of MIL/M-MeS cube produced satisfactory recoveries and repeatability. The LODs of the method when applied to spiked corn samples were in the range of 0.01-0.04 ng g-1 (LODs = 3δ/k). The relative intra- and inter-day recoveries ranged from 90.30 to 116.50% and 92.38-116.24%, respectively, and relative standard deviations ranged from 1.08 to 12.32% and 5.36-16.23%, respectively.

Development of a novel acidic task-specific ionic liquid-based effervescence-assisted microextraction method for determination of triazine herbicides in tea beverage.

In this study, a simple, rapid, sensitive and eco-friendly effervescence-assisted microextraction method was established for the determination of triazine herbicides in tea beverage samples. For the first time, acidic task-specific ionic liquid [C4mim][HSO4] was utilized not only as extraction solvent, but also as Brønsted acid to generate carbon dioxide which can enhance mass transfer between extraction solvent and analytes. Extraction parameters, including amounts of ionic liquid and sodium bicarbonate, concentration of salt, pH value of the sample solution and volume of elution solvent, were evaluated. Under the optimal conditions, the developed method had good linearity in the range of 1-200 ng mL-1 or 2-200 ng mL-1 with the correlation coefficients higher than 0.9990. Additionally, minimum detection and quantification limits were 0.08 ng mL-1 and 0.25 ng mL-1, respectively, precision was in the satisfactory range of 0.8%-9.3%, and recovery of the herbicides from the real samples, which was varied from 76.3% to 135.9%, was in the acceptable range. Moreover, stability of the analytes in sample solution and robustness of the experiment were measured and obtained satisfactory results. In addition, the method does not require external energy supplied by an external source or apparatus. These results demonstrate that the method could be applied for determining trace triazine herbicides in beverage samples.

Solid-phase microextraction of triazine herbicides via cellulose paper coated with a metal-organic framework of type MIL-101(Cr), and their quantitation by HPLC-MS.

Cellulose paper was coated with the metal-organic framework MIL-101(Cr) in a chitosan matrix and utilized for thin-film microextraction (TFME). The coated paper possesses excellent extraction efficiency for the triazine herbicides atraton, desmetryn, secbumeton, prometon, ametryn, dipropetryn, and dimethametryn. High-performance liquid chromatography-tandem mass spectrometry was applied to quantify target analytes. The effects of mass ratio of MIL-101(Cr) to chitosan, sample pH value, time of adsorption and desorption, and type and volume of desorption solvent on extraction efficiency were optimized. Under the optimal conditions, the method has limits of detection between 1.5 and 22 ng·L-1. The recoveries of triazines from spiked tap water, drinking water, lake water and river water range from 77.0 to 125.3%, with relative standard deviations of <17.4%. Graphical abstract Cellulose paper was modified with metal-organic framework MIL-101(Cr)/chitosan by using a simple, efficient and environmentally friendly approach. The modified cellulose paper was then used as a novel extraction phase in thin-film microextraction (TFME).

One-step synthesized magnetic MIL-101(Cr) for effective extraction of triazine herbicides from rice prior to determination by liquid chromatography-tandem mass spectrometry.

The magnetic metal-organic framework MIL-101(Cr) material-based solid-phase extraction method coupled with high-performance liquid chromatography and tandem mass spectrometry was applied to extract seven triazine herbicides in rices. Fe3 O4 /MIL-101(Cr) was synthesized using reduction-precipitation method, in which steps including pre-synthesis and modification of Fe3 O4 nanoparticles were by-passed. Various parameters including extraction solvent type and volume, ultrasonic extraction time, amount of Fe3 O4 /MIL-101(Cr) microspheres, adsorption time, desorption volume and time were investigated. Under optimal conditions, the proposed method had the limit of detection (S/N = 3) and the limit of quantification (S/N = 10) of 1.08-18.10 and 3.60-60.20 pg/g, respectively. Relative standard deviations calculated for all herbicides with concentrations of 2 and 20 ng/g were in the range of 0.5 to 13% (n = 3). In addition, at the two above-mentioned concentrations, the method achieved relative recoveries percentages of 79.3 to 116.7% when applied to determine the triazine herbicides in real samples spiked. This rapid, green, non-polluting, pre-concentrated extraction method was successfully developed and applied to analyze herbicides in rice samples.

Packed hybrids of gold nanoparticles and halloysite nanotubes for dispersive solid phase extraction of triazine herbicides, and their subsequent determination by HPLC.

Halloysite nanotubes (HNTs) were functionalized with gold nanoparticles. The morphology and structures of this composite were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, powder X-ray diffraction, and surface area and pore-size analyses. The material was employed, in conjunction with a syringe pump and an organic filter head, to the enrichment of five triazines (atrazine, desmetryn, prometorn, tebumeton, ametryn) in spiked rice samples. Several parameters that may affect the extraction efficiencies, including type and volume of extraction solvent, amount of sorbent, times of ultrasonic extraction and adsorption, volume and flow rate of elution solvent, were optimized. Following elution with acetonitrile, the herbicides were quantified by using HPLC. Under the optimum conditions, the LODs of the method, when applied to spiked rice samples, are the range from 0.06 to 1.32 ng g-1 (LODs = 3SD/k). The relative intra-day and inter-day recoveries ranged from 80.6 to 106.5% and 80.4-107.3%, respectively, and relative standard deviations ranged from 0.8 to 8.7% and 3.6-9.6%, respectively. Graphical abstract Packed hybrids of gold nanoparticles and halloysite nanotubes (Au/HNTs) were prepared and applied to the dispersive solid-phase extraction by packed sorbent of five triazine herbicides from rice.