Ionic liquid-based ultrasound-assisted dispersive liquid–liquid microextraction followed high-performance liquid chromatography for the determination of ultraviolet filters in environmental water samples

In the present study, a rapid, highly efficient and environmentally friendly sample preparation method named ionic liquid-based ultrasound-assisted dispersive liquid–liquid microextraction (IL-USA-DLLME), followed by high performance liquid chromatography (HPLC) has been developed for the extraction and preconcentration of four benzophenone-type ultraviolet (UV) filters (viz. benzophenone (BP), 2-hydroxy-4-methoxybenzophenone (BP-3), ethylhexyl salicylate (EHS) and homosalate (HMS)) from three different water matrices. The procedure was based on a ternary solvent system containing tiny droplets of ionic liquid (IL) in the sample solution formed by dissolving an appropriate amount of the IL extraction solvent 1-hexyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate ([HMIM][FAP]) in a small amount of water-miscible dispersive solvent (methanol). An ultrasound-assisted process was applied to accelerate the formation of the fine cloudy solution, which markedly increased the extraction efficiency and reduced the equilibrium time. Various parameters that affected the extraction efficiency (such as type and volume of extraction and dispersive solvents, ionic strength, pH and extraction time) were evaluated. Under optimal conditions, the proposed method provided good enrichment factors in the range of 354–464, and good repeatability of the extractions (RSDs below 6.3%, n = 5). The limits of detection were in the range of 0.2–5.0 ng mL⁻¹, depending on the analytes. The linearities were between 1 and 500 ng mL⁻¹ for BP, 5 and 500 ng mL⁻¹ for BP-3 and HMS and 10 and 500 ng mL⁻¹ for EHS. Finally, the proposed method was successfully applied to the determination of UV filters in river, swimming pool and tap water samples and acceptable relative recoveries over the range of 71.0–118.0% were obtained.     

Ionic liquid-based dispersive liquid–liquid microextraction for the separation and preconcentration of lead in water samples prior to FAAS determination without chelating agent

In the present study, an environment-friendly sample preparation method termed ionic liquid-based dispersive liquid–liquid microextraction combined with flame atomic absorption spectrometry has been developed for the determination of Pb(II) ion in water samples prior to flame atomic absorption spectrometry determination. In this method, ionic liquid was used as an extraction solvent instead of the organic solvent used in the conventional dispersive liquid–liquid microextraction (DLLME) assay, and there is no need for a chelating agent. Several variables that may affect extraction efficiencies, including pH, the volume of ionic liquid, the type and volume of disperser solvent, salt addition, and the time for centrifugation and extraction were studied and optimised. Under the optimised conditions, the calibration curve exhibited linearity over the range of 20.0–1000.0 μg L^?1. The enrichment factor and the limit of detection based on 3S_b/m were 35.0 and 5.9 μg L^?1, respectively. Seven replicate determination of a solution containing of 100.0 μg L^?1 Pb(II) ions gave a relative standard deviation of ±2.1%. Finally, the feasibility of the proposed method for Pb(II) determination was assessed by the analysis of certi?ed reference material and various water samples and the satisfactory results were obtained.     

New temperature-assisted ionic liquid-based dispersive liquid–liquid microextraction method for the determination of glyphosate and aminomethylphosphonic acid in water samples

A new analytical temperature-assisted ionic liquid-based dispersive liquid–liquid microextraction (TA-IL-DLLME) method was developed for glyphosate and aminomethylphosphonic acid determination in water samples. Extracted analytes were derivatized using 9-fluoroenylmethylchloroformate and quantified by liquid chromatography with fluorescence detection. For the TA-IL-DLLME method, two strategies for phase solubilization were evaluated; in approach 1, the ionic liquid and aqueous matrix sample were mixed and then heated, while in approach 2, the aqueous sample was first heated and then the ionic liquid was injected. For both approaches, optimization included parameters that significantly affect extraction efficiency: ionic liquid type and volume, solubilization temperature and time, cooling and centrifugation time. Among the evaluated ionic liquids, 1-decyl-3-methylimidazolium tetrafluoroborate showed the best performance for TA-IL-DLLME and was selected for the two solubilization approaches; with approach 2, slightly better results were obtained. Thus, sample analyses were performed using a procedure based on approach 2. An important matrix effect, attributed to the presence of salts and metals in real water samples was observed. Sample acidification before derivatization allowed this problem to diminish, with recoveries ranging from 75 and 99%, and enrichment factors between 57 and 76 for target analytes.     

A new treatment by dispersive liquid–liquid microextraction for the determination of parabens in human serum samples

Alkyl esters of p-hydroxybenzoic acid (parabens) are a family of compounds that have been in use since the 1920s as preservatives in cosmetic formulations, with one of the lowest rates of skin problems reported in dermatological patients. However, in the last few years, many scientific publications have demonstrated that parabens are weak endocrine disruptors, meaning that they can interfere with the function of endogenous hormones, increasing the risk of breast cancer. In the present work, a new sample treatment method is introduced based on dispersive liquid–liquid microextraction for the extraction of the most commonly used parabens (methyl-, ethyl-, propyl-, and butylparaben) from human serum samples followed by separation and quantification using ultrahigh performance liquid chromatography–tandem mass spectrometry. The method involves an enzymatic treatment to quantify the total content of parabens. The extraction parameters (solvent and disperser solvent, extractant and dispersant volume, pH of the sample, salt addition, and extraction time) were accurately optimized using multivariate optimization strategies. Ethylparaben ring ¹³C₆-labeled was used as surrogate. Limits of quantification ranging from 0.2 to 0.7 ng mL^?1 and an interday variability (evaluated as relative standard deviations) from 3.8 to 11.9 % were obtained. The method was validated using matrix-matched calibration standard and a spike recovery assay. Recovery rates for spiked samples ranged from 96 to 106 %, and a good linearity up to concentrations of 100 ng mL^?1 was obtained. The method was satisfactorily applied for the determination of target compounds in human serum samples.     

Ionic liquid ultrasound assisted dispersive liquid–liquid/micro-volume back extraction procedure for preconcentration and determination of ultra trace amounts of thallium in water and biological samples

A simple, highly sensitive and environment-friendly method, combined with flame atomic absorption spectroscopy (FAAS) is developed to preconcentrate and determine trace amounts of thallium in aqueous solutions. In the preconcentration step, the thallium (I) from 30?mL of an aqueous solution was extracted into 350?µL of ionic liquid, 1-hexyl-3-methylimidazolium hexa?uorophosphate [Hmim][PF₆], containing dicyclohexyl-18-crown-6 (DCH-18-crown-6) as complexing agent. Subsequently, the DCH-18-crown-6 complex was back-extracted into 300?µL of nitric acid (2?mol?L^?1) solution, and analyzed by FAAS. Several parameters in?uencing the extraction and determination of thallium, such as pH, concentration of DCH-18-crown-6, sonication and centrifugation times, sample volume, ionic liquid amounts, ionic strength, and concentration of stripping acid solution, were optimized. Under optimum conditions, the calibration graph was linear in the range of 5 to 400?ng?mL^?1, the detection limit was 0.64?ng?mL^?1 (3S_b/m, n?=?7), the enhancement factor was 98.2 and the relative standard deviation was ±1.43%. The results for preconcentration and determination of trace amount of thallium in waste water, well water, tap water, sea water, human hair and nail demonstrated the accuracy, recovery and applicability of the presented method.     

In-syringe demulsified dispersive liquid–liquid microextraction and high performance liquid chromatography–mass spectrometry for the determination of trace fungicides in environmental water samples

An in-syringe demulsified dispersive liquid–liquid microextraction (ISD–DLLME) technique was developed using low-density extraction solvents for the highly sensitive determination of the three trace fungicides (azoxystrobin, diethofencarb and pyrimethanil) in water samples by high performance liquid chromatography–mass spectrometry chromatography–diode array detector/electrospray ionisation mass spectrometry. In the proposed technique, a 5-mL syringe was used as an extraction, separation and preconcentration container. The emulsion was obtained after the mixture of toluene (extraction solvent) and methanol (dispersive solvent) was injected into the aqueous bulk of the syringe. The obtained emulsion cleared into two phases without centrifugation, when an aliquot of methanol was introduced as a demulsifier. The separated floating organic extraction solvent was impelled and collected into a pipette tip fitted to the tip of the syringe. Under the optimal conditions, the enrichment factors for azoxystrobin, diethofencarb and pyrimethanil were 239, 200, 195, respectively. The limits of detection, calculated as three times the signal-to-noise ratio (S N⁻¹), were 0.026 μg L⁻¹ for azoxystrobin, 0.071 μg L⁻¹ for diethofencarb and 0.040 μg L⁻¹ for pyrimethanil. The repeatability study was carried out by extracting the spiked water samples at concentration levels of 0.02 μg mL⁻¹ for all the three fungicides. The relative standard deviations varied between 4.9 and 8.2% (n = 5). The recoveries of all the three fungicides from tap, lake and rain water samples at spiking levels of 0.2, 1, 5 μg L⁻¹ were in the range of 90.0–105.0%, 86.0–114.0% and 88.6–110.0%, respectively. The proposed ISD–DLLME technique was demonstrated to be simple, practical and efficient for the determination of different kinds of fungicide residues in real water samples.     

One-step in-syringe dispersive liquid–liquid microextraction and GC-FID determination of trace amounts of di(2-ethylhexyl) phthalate and its metabolite in human urine samples

Di(2-ethylhexyl) phthalate (DEHP) is used as plasticizer in polyvinylchloride (PVC) plastics. Its metabolites and the parent phthalates are considered toxic. As the DEHP plasticizers are not chemically bound to PVC, they can migrate, evaporate or be leached into indoor air and atmosphere, foodstuff, and other materials. We have reported a novel, easy and available analytical method for the determination of DEHP and its metabolite, mono(2-ethylhexyl) phthalate (MEHP) in human urine samples by the in-syringe dispersive liquid–liquid microextraction method coupled with gas chromatography with flame ionization detector. The limits of detection and precision (RSD) were 2.5 μg/L and 1.4% for DEHP and 1.1 μg/L and 3.0% for MEHP, respectively. This method could be utilized for routine monitoring of the trace DEHP and MEHP in urine of human exposure to plasticizers.     

Flotation-assisted dispersive liquid–liquid microextraction method for preconcentration and determination of trace amounts of cobalt: Orthogonal array design

A simple, rapid, and efficient flotation-assisted dispersive liquid–liquid microextraction method was developed for preconcentration of trace amount of cobalt(II) ions. In this technique, a mixture of toluene and methanol (20: 80, v/v) was injected through the septum in the bottom of a narrow-bore tube containing cobalt solution. Afterwards, the fine droplets of extraction solvent were formed and cobalt (as 1-nitroso-2- naphtol complex) was collected on the surface of solution by aeration. The effect of different variables on the extraction efficiency of cobalt such as pH of solution, ligand concentration and injection volume was investigated using orthogonal array design. At optimum conditions, the calibration curve was linear over the range of 10–1000 μg/L. The detection limit, relative standard deviation and enrichment factor were 3 μg/L, 3.9% (n = 10) and 120, respectively. The developed method was successfully applied to the determination of cobalt in water and drug samples.     

Ultrasound-enhanced surfactant-assisted dispersive liquid–liquid microextraction and high-performance liquid chromatography for determination of ketoconazole and econazole nitrate in human blood

A simple and efficient method, based on ultrasound-enhanced surfactant-assisted dispersive liquid–liquid microextraction (UESA-DLLME) followed by high-performance liquid chromatography (HPLC) has been developed for extraction and determination of ketoconazole and econazole nitrate in human blood samples. In this method, a common cationic surfactant, cetyltrimethylammonium bromide (CTAB), was used as dispersant. Chloroform (40 μL) as extraction solvent was added rapidly to 5 mL blood containing 0.068 mg mL⁻¹ CTAB. The mixture was then sonicated for 2 min to disperse the organic chloroform phase. After the extraction procedure, the mixture was centrifuged to sediment the organic chloroform phase, which was collected for HPLC analysis. Several conditions, including type and volume of extraction solvent, type and concentration of the surfactant, ultrasound time, extraction temperature, pH, and ionic strength were studied and optimized. Under the optimum conditions, linear calibration curves were obtained in the ranges 4–5000 μg L⁻¹ for ketoconazole and 8–5000 μg L⁻¹ for econazole nitrate, with linear correlation coefficients for both >0.99. The limits of detection (LODs, S/N = 3) and enrichment factors (EFs) were 1.1 and 2.3 μg L⁻¹, and 129 and 140 for ketoconazole and econazole nitrate, respectively. Reproducibility and recovery were good. The method was successfully applied to the determination of ketoconazole and econazole nitrate in human blood samples.     

Solvent-based de-emulsification dispersive liquid–liquid microextraction combined with gas chromatography–mass spectrometry for determination of trace organochlorine pesticides in environmental water samples

In this work, we propose solvent-based de-emulsification dispersive liquid–liquid microextraction (SD-DLLME) as a simple, rapid and efficient sample pretreatment technique for the extraction and preconcentration of organochlorine pesticides (OCPs) from environmental water samples. Separation and analysis of fifteen OCPs was carried out by gas chromatography–mass spectrometry (GC/MS). Parameters affecting the extraction efficiency were systematically investigated. The detection limits were in the range of 2–50 ng L⁻¹ using selective ion monitoring (SIM). The precision of the proposed method, expressed as relative standard deviation, varied between 3.5 and 10.2% (n = 5). Results from the analysis of spiked environmental water samples at the low-ppb level met the acceptance criteria set by the EPA.     

Application of dispersive liquid–liquid microextraction and reversed phase-high performance liquid chromatography for the determination of two fungicides in environmental water samples

Dispersive liquid–liquid microextraction (DLLME) has been developed for the extraction and preconcentration of diethofencarb (DF) and pyrimethanil (PM) in environmental water. In the method, a suitable mixture of extraction solvent (50 µL carbon tetrachloride) and dispersive solvent (0.75 mL acetonitrile) are injected into the aqueous samples (5.00 mL) and the cloudy solution is observed. After centrifugation, the enriched analytes in the sediment phase were determined by HPLC-VWD. Different influencing factors, such as the kind and volume of extraction and dispersive solvent, extraction time and salt effect were investigated. Under the optimum conditions, the enrichment factors for DF and PM were both 108 and the limit of detection were 0.021 ng mL^?1 and 0.015 ng mL^?1, respectively. The linear ranges were 0.08–400 ng mL^?1 for DF and 0.04–200 ng mL^?1 for PM. The relative standard deviation (RSDs) were both almost at 6.0% (n = 6). The relative recoveries from samples of environmental water were from the range of 87.0 to 107.2%. Compared with other methods, DLLME is a very simple, rapid, sensitive (low limit of detection) and economical (only 5 mL volume of sample) method.     

Low-density magnetofluid dispersive liquid–liquid microextraction for the fast determination of organochlorine pesticides in water samples by GC-ECD

A new micro-extraction technique named low-density magnetofluid dispersive liquid–liquid microextraction (LMF-DMMLE) has been developed, which permits a wider range of solvents and can be combined with various detection methods. Comparing with the existing low density solvents micro-extraction methods, no special devices and complicated operations were required during the whole extraction process. Dispersion of the low-density magnetofluid into the aqueous sample is achieved by using vortex mixing, so disperser solvent was unnecessary. The extraction solvent was collected conveniently with an external magnetic field placed outside the extraction container after dispersing. Then, the magnetic nanoparticles were easily removed by adding precipitation reagent under the magnetic field. In order to evaluate the validity of this method, ten organochlorine pesticides (OCPs) were chosen as the analytes. Parameters influencing the extraction efficiency such as extraction solvents, volume of extraction solvents, extraction time, and ionic strength were investigated and optimized. Under the optimized conditions, this method showed high extraction efficiency with low limits of detection of 1.8–8.4 ng L⁻¹, good linearity in the range of 0.05–10.00 μg L⁻¹ and the precisions were in the range of 1.3–9.6% (RSD, n = 5). Finally, this method was successfully applied in the determination of OCPs in real water samples.     

Ultrasound-assisted dispersive liquid–liquid microextraction for the determination of six pyrethroids in river water

A simple ultrasound-assisted dispersive liquid–liquid microextraction method combined with liquid chromatography was developed for the preconcentration and determination of six pyrethroids in river water samples. The procedure was based on a ternary solvent system to formatting tiny droplets of extractant in sample solution by dissolving appropriate amounts of water-immiscible extractant (tetrachloromethane) in watermiscible dispersive solvent (acetone). Various parameters that affected the extraction efficiency (such as type and volume of extraction and dispersive solvent, extraction time, ultrasonic time, and centrifuging time) were evaluated. Under the optimum condition, good linearity was obtained in a range of 0.00059–1.52 mg L⁻¹ for all analytes with the correlation coefficient (r²) > 0.999. Intra-assay and inter-assay precision evaluated as the relative standard deviation (RSD) were less than 3.4 and 8.9%. The recoveries of six pyrethroids at three spiked levels were in the range of 86.2–109.3% with RSD of less than 8.7%. The enrichment factors for the six pyrethroids were ranged from 767 to 1033 folds.     

Rapid determination of ultra-trace amounts of acrylamide contaminant in water samples using dispersive liquid–liquid microextraction coupled to gas chromatography-electron capture detector

The objective of the present study was to develop and validate a rapid, highly sensitive, and reliable extraction method to determine acrylamide in water samples. The method was based on the derivatisation of the acrylamide in the presence of KBr, HBr and saturated Br₂ solution into 2,3-dibromopropionamide and dispersive liquid–liquid microextraction (DLLME) followed by gas chromatography–electron capture detection (GC–ECD) of the analyte. Different parameters that affect the DLLME process such as types and volumes of disperser solvent, ionic strength of aqueous solution and extraction time were investigated and optimised. Under optimal conditions, excellent linearity was obtained between concentration of acrylamide and the response of ECD with correlation of determination (R²) of 0.9999. The precision of the method, which was determined by calculating the relative standard deviations (RSD) of the at least three replicate measurements, was 3.6%. The method presented in this study is sensitive enough for the determination of acrylamide in different water samples with the limit of detection (LOD) value of 1?ng?L^?1. The mean percentage recoveries exceeded 91% for all of spiking levels in the real water samples. The results obtained from DLLME method are validated by EPA method 8032A.     

A dispersive liquid–liquid microextraction based on a task-specific ionic liquid for enrichment of trace quantity of cadmium in water and food samples

In this work, a hydrophilic task-specific ionic liquid (TSIL) of 1-chloroethyl-3-methylimidazolium chloride functionalized with 8-hydroxyquinoline was used in a dispersive liquid–liquid microextraction method followed by flame atomic absorption spectrometry for the enrichment and determination of trace amounts of cadmium (Cd²⁺) ions. The simultaneous chelation and extraction of Cd²⁺ ions was carried out by the TSIL. Fine droplets of the water-immiscible TSIL containing target analyte were generated in situ by addition of an anion exchanger potassium hexafluorophosphate (KPF₆) salt to the sample tube. After phase separation by centrifugation for 4 min, the sedimented TSIL was diluted with acidified ethanol for measurement of Cd²⁺ content. Some significant parameters influence the preconcentration of Cd²⁺ ions such as sample pH, TSIL volume, amount of KPF₆, non-ionic surfactant and salt concentration were investigated. Under the optimal conditions, calibration curve was linear in the range of 5–250 µg L^?1 Cd²⁺ with correlation coefficient of 0.9975 and a detection limit of 0.55 µg L^?1. The relative standard deviation for six replicate measurements of 50 µg L^?1 Cd²⁺ was 1.5%. The method was successfully applied for the extraction and determination of Cd²⁺ ions in water and food samples.     

Trace determination of EDTA from water samples using dispersive liquid–liquid microextraction coupled with HPLC-DAD

Dispersive liquid–liquid microextraction (DLLME) in conjunction with high-performance liquid chromatography-diode array detection (HPLC-DAD) has been applied to the extraction and determination of EDTA in sediments and water samples. The effect of extraction, nature and volume of disperser solvent, pH value of sample solution, extraction time and extraction temperature were investigated. Under the optimal conditions the analytical range of EDTA was from 3.0 to 50.0 μg L^?1 with a correlation coefficient of 0.9982 and a detection limit of 1.7 μg L^?1. The relative standard deviation (RSD) was less than 5.4% (n?=?5), and the recovery values were in the range of 89–95%. The simplicity, high enrichment, high recovery and good repeatability are the main advantages of the method presented. The DLLME-HPLC-DAD method was successfully applied to the analysis of EDTA in aqueous samples.     

Ultrasound-assisted dispersive liquid–liquid microextraction and multivariate optimization for determination of Sodium Closantel in biological samples and pharmaceutical formula

A fast and simple ultrasound-assisted dispersive liquid–liquid microextraction method for determination of Sodium Closantel has been developed. High-performance liquid chromatography with ultraviolet detector has been used for the determination of Sodium Closantel. The effect of influencing parameters such as type and volume of extraction and disperser solvents, pH of sample solution, extraction time and amount of salt was also investigated. Optimization of method was performed using Plackett–Burman experimental design and surface response methodology. Under the optimal conditions, the linear dynamic range of Sodium Closantel was from 10 to 3000 µg L^?1 with a correlation coefficient of 0.997 and a detection limit of 1.0 µg L^?1. The relative standard deviation was less than 3.5% (n = 5). The method has been successfully applied for determination of Sodium Closantel in real samples. The enrichment factor was 48 under optimal conditions.     

Ionic liquids versus ionic liquid-based surfactants in dispersive liquid–liquid microextraction for determining copper in water by flame atomic absorption spectrometry

This work compares the performance of dispersive liquid–liquid method (DLLME) as a prior step for determining copper by flame atomic absorption spectrometry (FAAS), when using the ionic liquid (IL) 1-butyl-3-methylimidazolium hexafluorophosphate (C₄MIm-PF₆) or the IL-based surfactant 1-hexadecyl-3-butylimidazolium bromide (C₁₆C₄Im-Br) as extractant solvents. For the water-insoluble C₄MIm-PF₆, the most conventional DLLME mode using acetonitrile as dispersive solvent was employed. For the water-soluble C₁₆C₄Im-Br, the in situ DLLME mode with lithium bis[(trifluoromethane)sulfonyl]imide (Li-NTf₂) as metathesis reagent was employed. In both approaches, some effective parameters such as volumes of extractant and dispersive solvents, concentration of complexing agent, pH of sample solution, salting-out effect and final diluting solvent to ensure compatibility with FAAS, were properly optimised. The optimum conditions for the IL-DLLME method using C₄MIm-PF₆ were: 100 μL of neat C₄MIm-PF₆, 1 mL of acetonitrile, 10 mL of water, no control of pH for environmental waters, NaCl content of 23 g L^?1, diethyl dithiocarbamate (DDTC) as complexing agent at 10 mg L^?1 and final dilution of the micro-droplet with acetonitrile up to 70 µL. The optimum conditions for the in situ IL-DLLME method using C₁₆C₄Im-Br were: 0.8 mL of acetonitrile, 10 mL of water containing C₁₆C₄Im-Br at 25.2 mmol L^?1, final dilution step of the micro-droplet with 200 µL of acetonitrile and remaining conditions as those of C₄MIm-PF₆. The analytical performance of both methods was similar, being slightly better for the IL-DLLME method using C₄MIm-PF₆, with limits of detection (LOD) of 3.3 µg L^?1 (versus 5.1 µg L^?1 when using C₁₆C₄Im-Br), precision values as intraday relative standard deviation (RSD in %) lower than 8.8% (being of 10% for the C₁₆C₄Im-Br method) and an enrichment factor of 54 (being 27 when using C₁₆C₄Im-Br). The DLLME-FAAS method with C₄MIm-PF₆ was used in the analysis of environmental waters with successful performance, with relative recoveries of 110% and 105%, and interday precision with RSD values of 21% and 7.4% for spiked levels of 60 and 160 µg L^?1, respectively. The results obtained when analysing an urban wastewater sample coming from an inter-laboratory exercise was comparable to those obtained for other 93 laboratories. The method was also valid for the determination of Cu²⁺ in presence of foreign ions commonly found in natural waters.