Application of supramolecular solvent based on the surface-active ionic liquid in dispersive liquid-liquid microextraction of triazine herbicides in tea samples.

In this study, a novel supramolecular solvent based on surface-active ionic liquid was prepared and used as an extraction solvent for dispersive liquid-liquid microextraction of four triazine herbicides in tea samples. The formation mechanism, microstructure and physicochemical properties of supramolecular solvent were studied. Some parameters, including the molar ratio of surface-active ionic liquid to tetrahydrofuran, volume of supramolecular solvent, vortex time, pH of sample solution, type and amount of salt, were investigated and optimized. The good linearities (r > 0.9990) for the analytes were obtained. The limits of detection and quantification for triazine herbicides were in the range of 1.7-2.1 µg kg-1 and 5.6-7.1 µg kg-1, respectively. The spiked recoveries were 80.0-119.9 %. The supramolecular solvent prepared in this study has the advantages of simple preparation process, low viscosity and good dispersibility. It can be used for the extraction and enrichment of trace triazine herbicides in tea samples.

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.

Facile preparation of carbon nanotube-based molecularly imprinted monolithic stirred unit.

A lab-made stirring extraction unit based on a selective monolithic solid was developed. The monolith was formed by interconnected carbon nanotubes which were covered by a thin polymeric layer, where specific cavities were generated to provide selective recognition sites in the material. To reach this goal, a water-in-oil (W/O) medium internal phase emulsion (40/60 w/w%), was prepared and photopolymerized. The polymerization reaction took place in the organic or external phase containing the carbon nanotubes, polymeric monomers (cross-linker and functional monomer) and a molecule template. Therefore, it was possible to coat the nanotubes with a layer of molecularly imprinted polymer (MIP) with the target analyte while forming a monolithic and macroscopic structure. The developed selective monolithic stirring extraction units were applied for the determination of secbumeton and structurally related compounds (triazine herbicides) in peppermint mint and tea samples. Their adsorption capacity and selectivity were also compared with a non-imprinted polymer (NIP). Finally, the performance of the method was evaluated for quantitative analysis, achieving limits of detection (LODs) between 0.4 and 2.5 µg·L-1. The intra- and inter-day precision of the method was also evaluated as relative standard deviation, observing values which ranged from 3% to 9% and 9% to 15%, respectively. Graphical Abstract.

Vortex-assisted deep eutectic solvent reversed-phase liquid-liquid microextraction of triazine herbicides in edible vegetable oils.

In this study, four triazine herbicides-namely, simazine, ametryn, prometryn and terbuthylazine-were separated and determined using high-performance liquid chromatography coupled with ultraviolet detector (HPLC-UVD). The deep eutectic solvent (DES) formed by tetrabutylammonium chloride ([N4444]Cl, TBA) and ethylene glycol (EG) was selected as the extraction solvent of vortex-assisted reversed-phase liquid-liquid microextraction (VA-RPLLME). The application of the hydrophilic DES expands the range of choice for LLME. The experimental parameters affecting the extraction recoveries, including the amount of the DES, the sample volume and the vortex time, were investigated and optimized by the design of experiments (DoE) methodology. A quadratic model, namely central composite face-centered (CCF) design featuring 20 runs was used instead of the conventional trial and error approach. Under optimum conditions, the limits of determination (LODs) of the method were 0.60-1.50 µg L-1. The enrichment factors for the analytes ranged from 27 to 31. The extraction recoveries were in the range of 84.1-104.9%, and the intra-day, inter-day and intermediate relative standard deviations (RSDs) were less than 8.4%. Finally, the method was applied for the determination of triazine herbicides in vegetable oil samples. The obtained recoveries were in the range of 60.1-107.2% and RSDs were lower than 8.1%. In general, VA-RPLLME can be complementary to the present available methods for the determination of triazine herbicides in vegetable oil samples.

Determination of triazine herbicides and their metabolites in multiple medicinal parts of traditional Chinese medicines using streamlined pretreatment and UFLC-ESI-MS/MS.

A rapid, sensitive, and reliable ultra-fast liquid chromatography combined with electrospray ionization tandem mass spectrometry (UFLC-ESI-MS/MS) method was established and applied to simultaneous determination of 31 triazine herbicides and their metabolites in multiple medicinal parts of traditional Chinese medicines (TCMs). A streamlined pretreatment approach using one-step extraction and dilution was proposed, which provided high-throughput processing, excellent recovery, and negligible interference. Afterwards, multiple-reaction monitoring (MRM) and information-dependent acquisition (IDA) triggered enhanced product ion spectra (EPI) was adopted to identify and quantify the targets in a single analysis. The optimized method was then validated according to the guidelines of the European Commission for the following parameters: Matrix effects, specificity, accuracy, precision, linearity, range, and stability. The LOD and LOQ for the 31 triazine herbicides were 0.1-10 µg kg-1 and 0.5-25 µg kg-1, respectively. Recoveries at three concentration levels were within 67.9-120.3% with an associated precision RSD <20%. Using the proposed approach, trazines herbicides were determined from 44 commercially available TCMs. The detection rate of triazine herbicides residues was 15.9% of the total samples. Among them, atrazine, simeton, and simetryn were found in the radix, herba, and seed TCMs with values far below the referenced maximum residue limits (MRLs), but no residues were detected in either the flos or fructus. Taken together, this method has the potential to provide a means for triazines screening in extensive matrices, thereby laying the foundation for pesticide registration on TCMs. Moreover, it has the potential to guide further triazine residue control in TCMs.

Molecularly imprinted solid phase extraction in a syringe filter for determination of triazine herbicides in Radix Paeoniae Alba by ultra-fast liquid chromatography.

A novel, cost-effective and simple solid phase extraction (SPE) method, by using a syringe connected with a nylon membrane filter as the adsorbent container, was developed for the extraction of triazine herbicides from Radix Paeoniae Alba (RPA) samples. The selective molecularly imprinted polymers (MIPs) synthesized with the template of atrazine were employed as the adsorbents for the enrichment and purification of analytes. The extraction parameters, including the volume and type of loading solvent, the type of washing solvent and eluting solvent, were investigated. Under the optimized conditions, the final extracts were analyzed by ultra-fast liquid chromatography (UFLC). Recoveries of the developed method range from 92.4% to 107.3% with intra- and inter-day relative standard deviations (RSDs) lower than 8.2%. The calibration curve is linear in the concentration range of 0.005-2.4 µg g(-1) for desmetryn, atrazine and terbumeton, and 0.005-1.5 µg g(-1) for dimethametryn and dipropetryn, with the correlation coefficient (R(2)) higher than 0.9995. The limits of detection (LODs) of five triazine herbicides are in the range of 0.09-0.39 ng g(-1), which are lower than the maximum residue levels (MRLs) established by various official organizations. Analytical results of three real Radix Paeoniae Alba samples indicate that the proposed method is cost-effective and easy-to-use than other routine pretreatment methods.

Magnetic ionic liquid-based dispersive liquid-liquid microextraction for the determination of triazine herbicides in vegetable oils by liquid chromatography.

Magnetic ionic liquid-based dispersive liquid-liquid microextraction (MIL-based DLLME) was developed for extracting triazine herbicides from vegetable oils. The MIL, 1-hexyl-3-methylimidazolium tetrachloroferrate ([C6mim] [FeCl4]), was used as the microextraction solvent. The magnetic separation time was shortened by simply mixing carbonyl iron powder with the MIL in the sample after DLLME. The effects of several important experimental parameters, including the amount of MIL, the time of ultrasonic extraction, the type and the volume of cleanup solvent were investigated. The MIL-based DLLME coupled with liquid chromatography gave the limits of detection of 1.31-1.49ngmL(-1) and limits of quantification of 4.33-4.91 ng mL(-1) for triazine herbicides. When the present method was applied to the analysis of vegetable oil samples, the obtained recoveries were in the range of 81.8-114.2% and the relative standard deviations were lower than 7.7%. Compared with existing methods, the performances achieved by the present method were acceptable.