Sanbing Zhang

Vortex-assisted magnetic β-cyclodextrin/attapulgite-linked ionic liquid dispersive liquid–liquid microextraction coupled with high-performance liquid chromatography for the fast determination of four fungicides in water samples

A novel microextraction technique combining magnetic solid-phase microextraction (MSPME) with ionic liquid dispersive liquid-liquid microextraction (IL-DLLME) to determine four fungicides is presented in this work for the first time. The main factors affecting the extraction efficiency were optimized by the one-factor-at-a-time approach and the impacts of these factors were studied by an orthogonal design. Without tedious clean-up procedure, analytes were extracted from the sample to the adsorbent and organic solvent and then desorbed in acetonitrile prior to chromatographic analysis. Under the optimum conditions, good linearity and high enrichment factors were obtained for all analytes, with correlation coefficients ranging from 0.9998 to 1.0000 and enrichment factors ranging 135 and 159 folds. The recoveries for proposed approach were between 98% and 115%, the limits of detection were between 0.02 and 0.04 μg L(-1) and the RSDs changed from 2.96 to 4.16. The method was successfully applied in the analysis of four fungicides (azoxystrobin, chlorothalonil, cyprodinil and trifloxystrobin) in environmental water samples. The recoveries for the real water samples ranged between 81% and 109%. The procedure proved to be a time-saving, environmentally friendly, and efficient analytical technique.

Ionic liquid-assisted liquid-phase microextraction based on the solidification of floating organic droplets combined with high performance liquid chromatography for the determination of benzoylurea insecticide in fruit juice.

A green, simple, and efficient method, ionic liquid-assisted liquid-liquid microextraction based on the solidification of floating organic droplets (ILSFOD-LLME) collected via a bell-shaped collection device (BSCD) coupled to high performance liquid chromatography with a variable-wavelength detector, was developed for the preconcentration and analysis of seven benzoylurea insecticides (BUs) in fruit juice. In the proposed method, the low-density solvent 1-dodecanol and the ionic liquid trihexyl(tetradecyl)phosphonium hexafluorophosphate ([P14, 6, 6, 6]PF6) were used as extractant. The extraction solvent droplet was easily collected and separated by the BSCD without centrifugation. The experimental parameters were optimized by the one-factor-at-a-time approach and were followed using an orthogonal array design. The results indicated the different effects of each parameter for extraction efficiency. Under the optimal conditions in the water model, the limits of detection for the analytes varied from 0.03 to 0.28μgL(-1). The enrichment factors ranged from 160 to 246. Linearities were achieved for hexaflumuron and flufenoxuron in the range of 0.5-500μgL(-1), for triflumuron, lufenuron and diafenthiuron in the range of 1-500μgL(-1), and for diflubenzuron and chlorfluazuron in the range of 5-500μgL(-1); the correlation coefficients for the BUs ranged from 0.9960 to 0.9990 with recoveries of 75.6-113.9%. Finally, the developed technique was successfully applied to real fruit juice with acceptable results. The relative standard deviations (RSDs) of the seven BUs at two spiked levels (50 and 200μgL(-1)) varied between 0.1% and 7.3%.

Effervescence-assisted β-cyclodextrin/attapulgite composite for the in-syringe dispersive solid-phase extraction of pyrethroids in environmental water samples

In this research, an effervescence-assisted β-cyclodextrin/attapulgite composite (β-CD/ATP) for the in-syringe dispersive solid-phase extraction (EAIS-DSPE) of pyrethroids in environmental samples was developed for the first time. A syringe was used to conduct the extraction procedure and a small amount of β-CD/ATP was dispersed into the solution with the release of carbon dioxide when the effervescent tablet components dissolved in water. Then, the sorbent was recovered using a filter membrane, and the analytes were directly eluted using acetonitrile. In the process, the β-CD/ATP sorbent resulted in an excellent extraction efficiency compared to commercially available sorbents such as C18 and HLB. Moreover, in the extraction procedure, both the β-cyclodextrin inclusion interactions (especially the hydrophobic effects) and the special structure of the ATP contributed to the efficient enrichment of pyrethroids in aqueous media. The amount of β-CD/ATP sorbent, the volume of desorption, the ratio of NaH2PO4/Na2CO3, the volume of the sample, and the pH were screened using a Plackett-Burman design. All factors affecting the procedure were optimized by applying a central composite design. Under the optimized conditions, a good repeatability (RSDs) ranging from 1.7 to 2.3, linearity (2.5-500μgL(-1)), limits of detection (LODs) (0.15-1.03μgL(-1)), and an acceptable recoveries (76.8-86.5%) were achieved. Finally, the proposed method was successfully applied for the determination of pyrethroids in environmental samples including river water, reservoir water and lake water.

Determination of benzoylurea insecticides in environmental water and honey samples using ionic-liquid-mingled air-assisted liquid–liquid microextraction based on solidification of floating organic droplets

A novel and simple ionic-liquid-mingled air-assisted liquid–liquid microextraction based on solidification of floating organic droplets combined with high performance liquid chromatography was developed for the determination of six benzoylureas (BUs) in water and honey samples. In this method, a mixture of low-density and low melting point extraction solvents and aqueous sample solutions was rapidly sucked up and injected several times using a glass syringe. The influence of the main factors on the efficiency of this procedure is studied. Under the optimal conditions, the enrichment factors (EFs) for BUs were acquired in the range of 144 to 187, limits of detection (LODs) were between 0.01 and 0.1 μg L−1 and limits of quantitation (LOQs) were changed in the range of 0.03 and 0.33 μg L−1. The obtained extraction recoveries ranged from 84.03% to 109.20% with intra-day lower than 4.5%, and inter-day precision lower than 6.5%. The method is successfully applied to determine the BUs in environmental water and honey samples with recoveries in the range of 78.57–109.72%, which proved the potential use of this method in real samples.

Optimization of dispersive liquid–liquid microextraction based on the solidification of floating organic droplets using an orthogonal array design and its application for the determination of fungicide concentrations in environmental water samples

A dispersive liquid-liquid microextraction method based on the solidification of floating organic droplets was developed as a simple and sensitive method for the simultaneous determination of the concentrations of multiple fungicides (triazolone, chlorothalonil, cyprodinil, and trifloxystrobin) in water by high-performance liquid chromatography with variable-wavelength detection. After an approach varying one factor at a time was used, an orthogonal array design [L25 (5(5))] was employed to optimize the method and to determine the interactions between the parameters. The significance of the effects of the different factors was determined using analysis of variance. The results indicated that the extraction solvent volume significantly affects the efficiency of the extraction. Under optimal conditions, the relative standard deviation (n = 5) varied from 2.3 to 5.5% at 0.1 μg/mL for each analyte. Low limits of detection were obtained and ranged from 0.02 to 0.2 ng/mL. In addition, the proposed method was applied to the analysis of fungicides in real water samples. The results show that the dispersive liquid-liquid microextraction based on the solidification of floating organic droplets is a potential method for detecting fungicides in environmental water samples, with recoveries of the target analytes ranging from 70.1 to 102.5%.

Using β-cyclodextrin/attapulgite-immobilized ionic liquid as sorbent in dispersive solid-phase microextraction to detect the benzoylurea insecticide contents of honey and tea beverages.

A green, simple, inexpensive dispersive solid-phase microextraction method coupled with high-performance liquid chromatography was developed for rapid screening and selective recognition of benzoylurea insecticides (BUs) in honey and tea beverages. A novel adsorbent, ionic liquid (IL)-modified β-cyclodextrin/attapulgite (β-CD/ATP), was prepared by immobilizing IL on the surface of β-CD/ATP. A series of demanding extraction conditions were investigated through the experimental design. Under optimum conditions, the limits of detection for the analytes varied from 0.12 to 0.21 μg L(-1). The enrichment factors ranged from 112 to 150 folds. Linearities in the range of 5-500 ng m L(-1) were achieved for four BUs, while the correlation coefficients ranged from 0.9997 to 1.0000 and the recoveries from 84.5% to 104.7%. The precision of this method for the four BUs corresponded to intra-day and inter-day RSDs% lower than 3.85%. Finally, the proposed technique was applied for the preconcentration of the BUs from real samples with satisfactory results.

Ionic liquid-based totally organic solvent-free emulsification microextraction coupled with high performance liquid chromatography for the determination of three acaricides in fruit juice

A novel, totally organic solvent-free emulsification microextraction (TEME) technique using ionic liquids (ILs) is proposed in this study. Seven bis(trifluoromethylsulfonyl)imide ionic liquids were synthesized. After comparing the physicochemical properties of the ionic liquids and their application to microextraction experiments, 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C6MIM][NTf2]), which has moderate surface tension and viscosity, was selected as the extraction solvent. The dispersion of ILs and mass transfer were accelerated by ultrasound irradiation and temperature control processes. Therefore, no dispersive organic solvent was needed. Several variables, such as ionic liquid volume, duration of the ultrasound extraction, dispersion temperature, ionic strength and centrifugation time were investigated and optimized. Under the optimum conditions, the calibration curve was linear in the range of 0.1-600 μg L(-1) for chlorfenapyr and fenpyroximate and 0.5-600 μg L(-1) for spirodiclofen, with correlation coefficients of 0.9994-0.9999. The enrichment factors were between 261 and 285. The limits of detection (LODs) were 0.02-0.06 μg L(-1). Real fruit juice samples (at fortified levels of 10 μg L(-1) and 30 μg L(-1)) were successfully analyzed using the proposed method. The relative recoveries and enrichment factors were in the range of 92-104%.

In-syringe dispersive liquid-liquid microextraction based on the solidification of ionic liquids for the determination of benzoylurea insecticides in water and tea beverage samples.

A novel in-syringe dispersive liquid-liquid microextraction based on the solidification of ionic liquids (in-syringe SIL-DLLME) was coupled with high-performance liquid chromatography-ultraviolet detector (HPLC-UVD) to detect five benzoylurea insecticides (BUs) in water and tea beverage samples. In this method, the hydrophobic ionic liquid [N8881][PF6] was formed in situ by the metathesis reaction between [N8881]Cl and the anion-exchange reagent KPF6 to extract the target analytes. The whole extraction procedure was performed in a syringe. The solidified extractant could be separated from the aqueous phase by exposing the emulsified extraction solution to an ice bath and then easily collected by squeezing out the aqueous phase through the prepared NWPP-based needle. Various parameters affecting the extraction efficiency, such as the amount of [N8881]Cl, the molar ratio of [N8881]Cl to KPF6, salt addition, cooling time, solution temperature, sample pH and sample volume, were evaluated. Under the optimized conditions, the proposed method was validated with satisfactory results: good linearities with coefficients of determination greater than 0.99 were obtained in the range of 2-500µgL-1; the limits of detection varied between 0.29 and 0.59µgL-1; the recoveries of the five benzoylurea insecticides ranged from 85.93% to 90.52%; and the intra-day (n=3) and inter-day (n=3) relative standard deviations were less than 5.36%. Finally, the proposed method was successfully used for the determination of BUs in real water and tea beverage samples.

Detection of triazole pesticides in environmental water and juice samples using dispersive liquid–liquid microextraction with solidified sedimentary ionic liquids

A novel in situ metathesis reaction combined with an ultrasound-assisted dispersive liquid–liquid microextraction based on the solidification of sedimentary ionic liquids (in situ UA-SSIL-DLLME) was combined with high-performance liquid chromatography (HPLC) to detect four triazole pesticides in water and juice samples. In this method, the hydrophobic ionic liquid [P4448][PF6], formed in situ by the hydrophilic ionic liquid [P4448]Br and the anion-exchange reagent KPF6, was used as the microextraction solvent. The extraction procedure was assisted by ultrasound at 50 W for 5 min. After centrifugation and cooling, [P4448][PF6] was sedimented at the bottom and easily collected by decanting the aqueous phase directly. Various parameters affecting the extraction efficiency, such as the quantity of [P4448]Br, the molar ratio of [P4448]Br to KPF6, salt addition, ultrasound time, centrifugation rate and time, and sample pH, were evaluated. Good linearities with correlation coefficients greater than 0.99 were obtained under the optimum conditions. The limits of detection varied between 0.90 and 1.38 μg L−1, and the enrichment factors were in the range of 94–101. The recoveries of these four triazole pesticides ranged from 85.18% to 91.14%, with relative standard deviations less than 4.86% and 5.87% for intra-day (n = 3) and inter-day (n = 3), respectively. The proposed method was then successfully applied to analyze the target compounds in environmental water and juice samples.

Dispersive micro‐solid‐phase extraction of benzoylurea insecticides in honey samples with a β‐cyclodextrin‐modified attapulgite composite as sorbent

A β-cyclodextrin-modified attapulgite composite was prepared and used as a dispersive micro-solid-phase extraction sorbent for the determination of benzoylurea insecticides in honey samples. Parameters that may influence the extraction efficiency, such as the type and volume of the eluent, the amount of the sorbent, the extraction time and the ionic strength were investigated and optimized using batch and column procedures. Under optimized conditions, good linearity was obtained for all of the tested compounds, with R(2) values of at least 0.9834. The limits of detection were determined in the range of 0.2-1.0 μg/L. The recoveries of the four benzoylurea insecticides in vitex honey and acacia honey increased from 15.2 to 81.4% and from 14.2 to 82.0%, respectively. Although the β-cyclodextrin-modified attapulgite composite did not show a brilliant adsorption capacity for the selected benzoylurea insecticides, it exhibited a higher adsorption capacity toward relatively hydrophobic compounds, such as chlorfluazuron and hexaflumuron (recoveries in vitex honey samples ranged from 70.0 to 81.4% with a precision of 1.0-3.7%). It seemed that the logPow of the benzoylurea insecticides is related to their recoveries. The results confirmed the possibility of using cyclodextrin-modified palygorskite in the determination of relatively hydrophobic trace pharmaceutical residues.