Temperature‐controlled liquid–liquid microextraction combined with high‐performance liquid chromatography for the simultaneous determination of diazinon and fenitrothion in water and fruit juice samples

A simple, environmentally benign, and rapid method based on temperature‐controlled liquid–liquid microextraction using a deep eutectic solvent was developed for the simultaneous extraction/preconcentration of diazinon and fenitrothion. The method involved the addition of deep eutectic solvent to the aqueous sample followed by heating the mixture in a 75°C water bath until the solvent was completely dissolved in the aqueous phase. Then, the resultant solution was cooled in an ice bath and a cloudy solution was formed. Afterward, the mixture was centrifuged and the enriched deep eutectic solvent phase was analyzed by high‐performance liquid chromatography with ultraviolet detection for quantification of the analytes. The factors affecting the extraction efficiency were optimized. Under the optimized extraction conditions, the limits of detection for diazinon and fenitrothion were 0.3 and 0.15 μg/L, respectively. The calibration curves for diazinon and fenitrothion exhibited linearity in the concentration range of 1–100 and 0.5–100 μg/L, respectively. The relative standard deviations for five replicate measurements at 10.0 μg/L level of analytes were less than 2.8 and 4.5% for intra‐ and interday assays, respectively. The developed method was successfully applied to the determination of diazinon and fenitrothion in water and fruit juice samples.     

Air‐assisted dispersive liquid–liquid microextraction based on a new hydrophobic deep eutectic solvent for the preconcentration of benzophenone‐type UV filters from aqueous samples

Deep eutectic solvents are considered as new and green solvents that can be widely used in analytical chemistry such as microextraction. In the present work, a new dl‐ menthol‐based hydrophobic deep eutectic solvent was synthesized and used as extraction solvents in an air‐assisted dispersive liquid–liquid microextraction method for preconcentration and extraction of benzophenone‐type UV filters from aqueous samples followed by high‐performance liquid chromatography with diode array detection. In an experiment, the deep eutectic solvent formed by dl‐ menthol and decanoic acid was added to an aqueous solution containing the UV filters, and then the mixture was sucked up and injected five times by using a glass syringe, and a cloudy state was achieved. After extraction, the solution was centrifuged and the upper phase was subjected to high‐performance liquid chromatography for analysis. Various parameters such as the type and volume of the deep eutectic solvent, number of pulling, and pushing cycles, solution pH and salt concentration were investigated and optimized. Under the optimum conditions, the developed method exhibited low limits of detection and limits of quantitation, good linearity, and precision. Finally, the proposed method was successfully applied to determine the benzophenone‐type filters in environmental water samples with relative recoveries of 88.8–105.9%.     

Vortex‐assisted natural deep eutectic solvent microextraction using response surface methodology optimization for determination of orthophosphate in water samples by molybdenum blue method

A new, rapid, and efficient microextraction technique named vortex‐assisted natural deep eutectic solvent microextraction has been developed for the preconcentration and determination of orthophosphate in real water samples. The method is based on the formation of the phosphomolybdenium blue complex followed by proposed microextraction procedure and subsequent spectrophotometric determination in a microcell. Screening study for the optimal composition of natural deep eutectic solvent was initially performed with different solvents, including choline chloride as hydrogen bond acceptor and different hydrogen bond donors. A ternary mixture of glucose‐choline chloride‐water was used as the most efficient extraction solvent. Response surface methodology based on the central composite design was used to optimize experimental parameters. Under optimal conditions, the calibration graph for orthophosphate determination was linear over the range of 2.0–80.0 µg/L (correlation coefficient of 0.9971) with a detection limit of 0.2 µg/L. The repeatability, reproducibility, and relative error values of the method were below 7%, indicating acceptable precision and accuracy. This approach, using natural deep eutectic solvent as an eco‐friendly solvent with high solubilization power and vortex mixing as an alternative energy source, represents a promising choice for a green separation and preconcentration methodology for determination of orthophosphate in real water samples.     

Temperature‐controlled ionic liquid dispersive liquid‐phase microextraction for the sensitive determination of triclosan and triclocarban in environmental water samples prior to HPLC‐ESI‐MS/MS

A novel dispersive liquid‐phase microextraction method without dispersive solvents has been developed for the enrichment and sensitive determination of triclosan and triclocarban in environmental water samples prior to HPLC‐ESI‐MS/MS. This method used only green solvent 1‐hexyl‐3‐methylimidazolium hexafluorophosphate as extraction solvent and overcame the demerits of the use of toxic solvents and the instability of the suspending drop in single drop liquid‐phase microextraction. Important factors that may influence the enrichment efficiencies, such as volume of ionic liquid, pH of solutions, extraction time, centrifuging time and temperature, were systematically investigated and optimized. Under optimum conditions, linearity of the method was observed in the range of 0.1–20 μg/L for triclocarban and 0.5–100 μg/L for triclosan, respectively, with adequate correlation coefficients (R>0.9990). The proposed method has been found to have excellent detection sensitivity with LODs of 0.04 and 0.3 μg/L, and precisions of 4.7 and 6.0% (RSDs, n=5) for triclocarban and triclosan, respectively. This method has been successfully applied to analyze real water samples and satisfactory results were achieved.     

On‐line extraction and determination of two herbicides: Comparison between two modes of three‐phase hollow fiber microextraction

Two different modes of three‐phase hollow fiber liquid‐phase microextraction were studied for the extraction of two herbicides, bensulfuron‐methyl and linuron. In these two modes, the acceptor phases in the lumen of the hollow fiber were aqueous and organic solvents. The extraction and determination were performed using an automated hollow fiber microextraction instrument followed by high‐performance liquid chromatography. For both three‐phase hollow fiber liquid‐phase microextraction modes, the effect of the main parameters on the extraction efficiency were investigated and optimized by central composite design. Under optimal conditions, both modes showed good linearity and repeatability, but the three‐phase hollow fiber liquid‐phase microextraction based on two immiscible organic solvents has a better extraction efficiency and figures of merit. The calibration curves for three‐phase hollow fiber liquid‐phase microextraction with an organic acceptor phase were linear in the range of 0.3–200 and 0.1–150 μg/L and the limits of detection were 0.1 and 0.06 μg/L for bensulfuron‐methyl and linuron, respectively. For the conventional three‐phase hollow fiber liquid‐phase microextraction, the calibration curves were linear in the range of 3.0–250 and 15–400 μg/L and LODs were 1.0 and 5.0 μg/L for bensulfuron‐methyl and linuron, respectively. The real sample analysis was carried out by three‐phase hollow fiber liquid phase microextraction based on two immiscible organic solvents because of its more favorable characteristics.     

Low‐density solvent‐based vortex‐assisted surfactant‐enhanced emulsification liquid–liquid microextraction and its application

For the first time, the low‐density solvent‐based vortex‐assisted surfactant‐enhanced emulsification liquid–liquid microextraction, followed by GC‐flame photometric detection has been developed for the determination of eight organophosphorus pesticides in aqueous samples. A small volume of organic extraction solvent (toluene) was dispersed into the aqueous samples by the assistance of surfactant and vortex agitator. The extraction was performed in a special disposable polyethylene pipette, allowing using the reagents with lower density than water as extraction solvents. The influence parameters were systemically investigated and optimized: toluene (30 μL) and Triton X‐100 (0.2 mmol/L) were used as the extraction solvent and the surfactant, respectively, and the extraction was performed for 1 min under room temperature without adding sodium chloride. Under the optimum conditions, the validation parameters such as the RSD (n = 6; 2.1–11.3%), LOD (0.005 and 0.05 μg/L), and linear range (0.1–50.0 μg/L with correlation coefficients (0.9958–0.9992) showed the method was satisfying. The proposed method has been successfully applied to the determination of the organophosphorus pesticides in real samples with recoveries between 82.8 and 100.2%.     

Characterization of Deep Eutectic Solvents for Dispersive Liquid–Liquid Microextraction for Phenolics

Dispersive liquid–liquid microextraction using deep eutectic solvents, as novel extraction solvents, was developed for the separation, preconcentration, and determination of chlorophenol, 2,3-dihydroxybenzoic acid, p-cresol, 4-chlorophenol, 2,4-dichlorophenol, and 2,4,6-trichlorophenol in vegetable oil. Seven deep eutectic solvents composed of choline chloride and different hydrogen bond donors (ethyl glycol, glycerol, 1,2-butanediol, 1,4-butanediol, 1,6-hexanediol, urea, and acetic acid) were characterized. The deep eutectic solvents formed by choline chloride-1,6-hexanediol in a 1:2 molar ratio provided the highest extraction efficiency. The sonication time, deep eutectic solvent volume, and disperser solvent were optimized. Under the optimal conditions of a sonication time of 11?min, a deep eutectic solvent volume of 90?µL, and acetone as the disperser solvent, extraction recoveries from 76.1 to 88.3% were obtained with 8.46 to 9.46 enrichment factors and the limits of detection exceeding 0.1?µg/mL with the relative standard deviations from 1.0 to 3.5%. This method using dispersive liquid–liquid microextraction with deep eutectic solvents is simple and provides high enrichment.     

Rapid pretreatment and determination of bisphenol A in water samples based on vortex‐assisted liquid–liquid microextraction followed by high‐performance liquid chromatography with fluorescence detection

A method for the rapid pretreatment and determination of bisphenol A in water samples based on vortex‐assisted liquid–liquid microextraction followed by high‐performance liquid chromatography with fluorescence detection was proposed in this paper. A simple apparatus consisting of a test tube and a cut‐glass dropper was designed and applied to collect the floating extraction drop in liquid–liquid microextraction when low‐density organic solvent was used as the extraction solvent. Solidification and melting steps that were tedious but necessary once the low‐density organic solvent used as extraction solvent could be avoided by using this apparatus. Bisphenol A was selected as model pollutant and vortex‐assisted liquid–liquid microextraction was employed to investigate the usefulness of the apparatus. High‐performance liquid chromatography with fluorescence detection was selected as the analytical tool for the detection of bisphenol A. The linear dynamic range was from 0.10 to 100 μg/L for bisphenol A, with good squared regression coefficient (r² = 0.9990). The relative standard deviation (n = 7) was 4.7% and the limit of detection was 0.02 μg/L. The proposed method had been applied to the determination of bisphenol A in natural water samples and was shown to be economical, fast, and convenient.     

Ultrapreconcentration and determination of organophosphorus pesticides in water by solid‐phase extraction combined with dispersive liquid–liquid microextraction and high‐performance liquid chromatography

Solid‐phase extraction coupled with dispersive liquid–liquid microextraction was developed as an ultra‐preconcentration method for the determination of four organophosphorus pesticides (isocarbophos, parathion‐methyl, triazophos and fenitrothion) in water samples. The analytes considered in this study were rapidly extracted and concentrated from large volumes of aqueous solutions (100 mL) by solid‐phase extraction coupled with dispersive liquid–liquid microextraction and then analyzed using high performance liquid chromatography. Experimental variables including type and volume of elution solvent, volume and flow rate of sample solution, salt concentration, type and volume of extraction solvent and sample solution pH were investigated for the solid‐phase extraction coupled with dispersive liquid–liquid microextraction with these analytes, and the best results were obtained using methanol as eluent and ethylene chloride as extraction solvent. Under the optimal conditions, an exhaustive extraction for four analytes (recoveries >86.9%) and high enrichment factors were attained. The limits of detection were between 0.021 and 0.15 μg/L. The relative standard deviations for 0.5 μg/L of the pesticides in water were in the range of 1.9–6.8% (n = 5). The proposed strategy offered the advantages of simple operation, high enrichment factor and sensitivity and was successfully applied to the determination of four organophosphorus pesticides in water samples.     

Simultaneous speciation of inorganic chromium(III) and chromium(VI) by hollow‐fiber‐based liquid‐phase microextraction coupled with HPLC–UV

The speciation of chromium(VI) and chromium(III) was investigated by using hollow fiber liquid‐phase microextraction based on two immiscible organic solvents followed by high performance liquid chromatography with ultraviolet detection. In this method, chromium(VI) and chromium(III) reacted with ammonium pyrrolidine dithiocarbamate to produce hydrophobic complexes. Subsequently, the complexes were first extracted into a thin layer of organic solvent (n‐dodecane) present in the pores of a porous hollow fiber, and then into a μL volume of an organic acceptor (methanol) located inside the lumen of the hollow fiber. Then, the extracting organic phase was injected into the separation column of the high‐performance liquid chromatograph for the analysis of both chromium species. Effective parameters on extraction were optimized using one‐variable‐at‐a‐time method and central composite design. Under optimized conditions, a linear range of 0.25–100 and 0.5–100 μg/L (R ² > 0.998), the limits of detection of (S/N = 3) 0.08 and 0.1 μg/L and a preconcentration factor of 625 and 556 were achieved for chromium(VI) and chromium(III), respectively. The method was successfully applied to the speciation and determination of chromium species in different water samples and satisfactory results were obtained.     

Selenium speciation in tea by dispersive liquid–liquid microextraction coupled to high‐performance liquid chromatography after derivatization with 2,3‐diaminonaphthalene

Selenium is an important element for human health, and it is present in many natural drinks and foods. Present study described a new method using dispersive liquid–liquid microextraction prior to high‐performance liquid chromatography with a UV variable wavelength detector for the determination of the total selenium, Se(IV), Se(VI), and total organoselenium in tea samples. In the procedure, 2,3‐diaminonaphthalene was used as the chelating reagent, 400 μL acetonitrile was used as the disperser solvent and 60 μL chlorobenzene was used as the extraction solvent. The complex of Se(IV) and 2,3‐diaminonaphthalene in the final extracted phase was analyzed by high‐performance liquid chromatography. The factors influencing the derivatization and microextraction were investigated. Under the optimal conditions, the limit of detection was 0.11 μg/L for Se(IV) and the linearity range was in the range of 0.5–40 μg/L. This method was successfully applied to the determination of selenium in four tea samples with spiked recoveries ranging from 91.3 to 100%.     

Dispersive liquid–liquid microextraction based on the solidification of deep eutectic solvent for the determination of benzoylureas in environmental water samples

We present a novel dispersive liquid–liquid microextraction method based on the solidification of deep eutectic solvent coupled with high‐performance liquid chromatography with a variable‐wavelength detection for the detection of five benzoylureas in real water samples. In this work, a green solvent consisting of 1‐octyl‐3‐methylimidazolium chloride and 1‐dodecanol was used as an extraction solvent, yielding the advantages of material stability, low density, and a suitable freezing point near room temperature. Parameters that significantly affect extraction efficiency were optimized by the one‐factor‐at‐a‐time approach. Under optimal conditions, the recoveries of five target compounds were obtained ranging from 87.39 to 98.05% with correlation coefficients ranging from 0.9994 to 0.9997 for pure water. The limits of detection were in the range of 0.09–0.16 μg/L. The enrichment factors were in the range of 171–188. Linearities were achieved in the range of 0.5–500 μg/L. The proposed method was successfully applied to determine benzoylureas in environmental water samples with a satisfactory recovery of approximately 81.38–97.67%.     

Simultaneous extraction and quantification of albendazole and triclabendazole using vortex‐assisted hollow‐fiber liquid‐phase microextraction combined with high‐performance liquid chromatography

A novel, simple, and rapid vortex‐assisted hollow‐fiber liquid‐phase microextraction method was developed for the simultaneous extraction of albendazole and triclabendazole from various matrices before their determination by high‐performance liquid chromatography with fluorescence detection. Several factors influencing the microextraction efficiency including sample pH, nature and volume of extraction solvent, ionic strength, vortex time, and sample volume were investigated and optimized. Under the optimal conditions, the limits of detection were 0.08 and 0.12 μg/L for albendazole and triclabendazole, respectively. The calibration curves were linear in the concentration ranges of 0.3–50.0 and 0.4–50.0 μg/L with the coefficients of determination of 0.9999 and 0.9995 for albendazole and triclabendazole, respectively. The interday and intraday relative standard deviations for albendazole and triclabendazole at three concentration levels (1.0, 10.0, and 30.0 μg/L) were in the range of 6.0–11.0 and 5.0–7.9%, respectively. The developed method was successfully applied to determine albendazole and triclabendazole in water, milk, honey, and urine samples.     

Use of volatile organic solvents in headspace liquid‐phase microextraction by direct cooling of the organic drop using a simple cooling capsule

A low‐cost and simple cooling‐assisted headspace liquid‐phase microextraction device for the extraction and determination of 2,6,6‐trimethyl‐1,3 cyclohexadiene‐1‐carboxaldehyde (safranal) in Saffron samples, using volatile organic solvents, was fabricated and evaluated. The main part of the cooling‐assisted headspace liquid‐phase microextraction system was a cooling capsule, with a Teflon microcup to hold the extracting organic solvent, which is able to directly cool down the extraction phase while the sample matrix is simultaneously heated. Different experimental factors such as type of organic extraction solvent, sample temperature, extraction solvent temperature, and extraction time were optimized. The optimal conditions were obtained as: extraction solvent, methanol (10 μL); extraction temperature, 60°C; extraction solvent temperature, 0°C; and extraction time, 20 min. Good linearity of the calibration curve (R² = 0.995) was obtained in the concentration range of 0.01–50.0 μg/mL. The limit of detection was 0.001 μg/mL. The relative standard deviation for 1.0 μg/mL of safranal was 10.7% (n = 6). The proposed cooling‐assisted headspace liquid‐phase microextraction device was coupled (off‐line) to high‐performance liquid chromatography and used for the determination of safranal in Saffron samples. Reasonable agreement was observed between the results of the cooling‐assisted headspace liquid‐phase microextraction high‐performance liquid chromatography method and those obtained by a validated ultrasound‐assisted solvent extraction procedure.     

Vortex‐assisted liquid–liquid microextraction for the rapid screening of short‐chain chlorinated paraffins in water

The rapid screening of trace levels of short‐chain chlorinated paraffins in various aqueous samples was performed by a simple and reliable procedure based on vortex‐assisted liquid–liquid microextraction combined with gas chromatography and electron capture negative ionization mass spectrometry. The optimal vortex‐assisted liquid–liquid microextraction conditions for 20 mL water sample were as follows: extractant 400 μL of dichloromethane; vortex extraction time of 1 min at 2500 × g; centrifugation of 3 min at 5000 × g; and no ionic strength adjustment. Under the optimum conditions, the limit of quantitation was 0.05 μg/L. Precision, as indicated by relative standard deviations, was less than 9% for both intra‐ and inter‐day analysis. Accuracy, expressed as the mean extraction recovery, was above 91%. The vortex‐assisted liquid–liquid microextraction with gas chromatography and electron capture negative ionization mass spectrometry method was successfully applied to quantitatively extract short‐chain chlorinated paraffins from samples of river water and the effluent of a wastewater treatment plant, and the concentrations ranged from 0.8 to 1.6 μg/L.     

Determination of desipramine in biological samples using liquid–liquid–liquid microextraction combined with in‐syringe derivatization,gas chromatography,and nitrogen/phosphorus detection

A method was established for the determination of desipramine in biological samples using liquid–liquid–liquid microextraction followed by in‐syringe derivatization and gas chromatography–nitrogen phosphorus detection. The extraction method was based on the use of two immiscible organic solvents. n‐Dodecane was impregnated in the pores of the hollow fiber and methanol was placed inside the lumen of the fiber as the acceptor phase. Acetic anhydride was used as the reagent for the derivatization of the analyte inside the syringe barrel. Parameters that affect the extraction efficiency (composition of donor and acceptor phase, ionic strength, sample temperature, and extraction time) as well as derivatization efficiency (amount of acetic anhydride and reaction time and temperature) were investigated. The limit of detection was 0.02 μg/L with intra and interday RSDs of 2.6 and 7.7%, respectively. The linearity of the method was in the range of 0.2–20 μg/L (r² = 0.9986). The method was successfully applied to determine desipramine in human plasma and urine.     

Determination of zearalenone in maize products by vortex‐assisted ionic‐liquid‐based dispersive liquid–liquid microextraction with high‐performance liquid chromatography

A novel method has been developed for the analysis of zearalenone in maize products by vortex‐assisted ionic‐liquid‐based dispersive liquid–liquid microextraction combined with HPLC and fluorescence detection. Maize samples were extracted with methanol/water (80:20, v/v) and the extraction solution was then used as the dispersive solvent in the microextraction procedure. The analyte was rapidly transmitted to a small volume of ionic liquid and was determined by HPLC. Various parameters affecting the recovery of the mycotoxin were investigated, such as the type and volume of the extraction solvent, the type and volume of the dispersive solvent, the pH of the aqueous phase, the salt addition, and the time of vortex and centrifugation. Under the optimal experimental conditions, a good linearity of the analyte was obtained in the range of 1.0–1000.0 μg/L with the correlation coefficient of 0.9998. The limit of detection (S/N = 3) and quantification (S/N = 10) were 0.3 and 1.0 μg/kg, and the mean recoveries ranged from 83.5 to 94.9%, with a relative standard deviation less than 5.0%. The proposed method was demonstrated to be simple, cheap, quick, and highly selective and was successfully applied to the determination of zearalenone in maize products.     

Simultaneous preconcentration and determination of 2,4‐D,alachlor and atrazine in aqueous samples using dispersive liquid–liquid microextraction followed by high‐performance liquid chromatography ultraviolet detection

Dispersive liquid–liquid microextraction coupled with high‐performance liquid chromatography‐ultraviolet detection as a fast and inexpensive technique was applied to the simultaneous extraction and determination of traces of three common herbicides, 2,4‐D, alachlor and atrazine, in aqueous samples. The critical experimental parameters, including type of the extraction and disperser solvents as well as their volumes, sample pH, salt addition, extraction time and centrifuging time, and speed were investigated and optimized. Under the optimum conditions, the calibration graphs found to be linear in the range of 0.3–200 μg/L with limits of detection in the range of 0.05–0.1 μg/L. The relative standard deviations were in the range of 4.5–6.2% (n = 7). The relative recoveries of well, tap, and river water samples which have been spiked with different levels of herbicides were 92.0–107.0, 82.0–104.0, and 82.0–86.0%, respectively.     

Development of Dispersive Liquid‐Liquid Microextraction Based on Solidification of Floating Organic Drop for the Determination of Trace Cobalt in Water Samples

A liquid‐phase microextraction technique was developed using dispersive liquid‐liquid microextraction based on solidification of floating organic drop combined with flame atomic absorption spectrometry, for the extraction and determination of trace amounts of cobalt in water samples. Microextraction efficiency factors, such as the type and volume of extraction and dispersive solvents, pH, extraction time, the chelating agent amount, and ionic strength were investigated and optimized. Under optimum conditions, an enrichment factor of 160 was obtained from 10.0 mL of water sample. The calibration graph was linearin the range of 1.15‐110 μg L^?1 with a detection limit of 0.35 μg L^?1. The relative standard deviation for ten replicate measurements of 10 and 100 μg L^?1 of cobalt were 3.26% and 2.57%, respectively. The proposed method was assessed through the analysis of certified reference water or recovery experiments.     

Vortex‐assisted liquid–liquid microextraction using a low‐toxicity solvent for the determination of five organophosphorus pesticides in water samples by high‐performance liquid chromatography

Vortex‐assisted liquid–liquid microextraction followed by high‐performance liquid chromatography with UV detection was applied to determine Isocarbophos, Parathion‐methyl, Triazophos, Phoxim and Chlorpyrifos‐methyl in water samples. 1‐Bromobutane was used as the extraction solvent, which has a higher density than water and low toxicity. Centrifugation and disperser solvent were not required in this microextraction procedure. The optimum extraction conditions for 15 mL water sample were: pH of the sample solution, 5; volume of the extraction solvent, 80 μL; vortex time, 2 min; salt addition, 0.5 g. Under the optimum conditions, enrichment factors ranging from 196 to 237 and limits of detection below 0.38 μg/L were obtained for the determination of target pesticides in water. Good linearities (r > 0.9992) were obtained within the range of 1–500 μg/L for all the compounds. The relative standard deviations were in the range of 1.62–2.86% and the recoveries of spiked samples ranged from 89.80 to 104.20%. The whole proposed methodology is simple, rapid, sensitive and environmentally friendly for determining traces of organophosphorus pesticides in the water samples.