Dispersive liquid–liquid microextraction based on solidification of floating organic droplet for the determination of triazine and triazoles in mineral water samples

A simple, rapid, and sensitive method for the determination of atrazine, simazine, cyproconazole, tebuconazole, and epoxiconazole in mineral water employing the dispersive liquid–liquid microextraction with solidification of a floating organic drop with determination by liquid chromatography tandem mass spectrometry has been developed. A mixed solution of 250 μL 1‐dodecanol and 1250 μL methanol was injected rapidly into 10 mL aqueous solution (pH 7.0) with 2% w/v NaCl. After centrifugation for 5 min at 2000 rpm, the organic solvent droplets floated on the surface of the aqueous solution and the floating solvent solidified. The method limits of detection were between 3.75 and 37.5 ng/L and limits of quantification were between 12.5 and 125 ng/L. The recoveries ranged from 70 to 118% for repeatability and between 76 and 95% for intermediate precision with a relative standard deviation from 2 to 18% for all compounds. Low matrix effect was observed. The proposed method can be successfully applied in routine analysis for determination of pesticide residues in mineral water samples, allowing for monitoring of triazine and triazoles at levels below the regulatory limits set by international and national legislations.     

Capillary electrophoresis determination of nonsteroidal anti‐inflammatory drugs in wastewater using hollow fiber liquid‐phase microextraction

The presence of pharmaceuticals in the environment due to growing worldwide consumption has become an important problem that requires analytical solutions. This paper describes a CE determination for several nonsteroidal anti‐inflammatory drugs (ibuprofen, naproxen, ketoprofen, diclofenac, ketorolac, aceclofenac and salicylic acid) in environmental waters using hollow fiber membrane liquid‐phase microextraction. The extraction was carried out using a polypropylene membrane supporting dihexyl ether and the electrophoretic separation was performed in acetate buffer (30 mM, pH 4) using ACN as the organic modifier. Detection limits between 0.25 and 0.86 ng/mL were obtained, respectively. The method could be applied to the direct determination of the seven anti‐inflammatories in wastewaters, and five of them have been determined or detected in different urban wastewaters.     

Application of dispersive liquid–liquid microextraction based on solidification of floating organic drop for simultaneous determination of alachlor and atrazine in aqueous samples

Dispersive liquid–liquid microextraction based on solidification of floating organic drop coupled with HPLC‐UV detection as a fast and inexpensive technique was applied to the simultaneous extraction and determination of traces of two common herbicides, 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, and extraction time were investigated and optimized. Under the optimum conditions, the calibration graphs found to be linear in the range of 0.1–200 μg/L with LOD in the range of 0.02–0.05 μg/L. The RSDs were in the range of 4.2–5.3% (n = 5). The relative recoveries of well, tap, and river water samples which have been spiked with different levels of herbicides were 94.0–106.0, 99.0–105.0, and 88.5–97.0%, respectively.     

A novel dispersive liquid-liquid microextraction based on solidification of floating organic droplet method for determination of polycyclic aromatic hydrocarbons in aqueous samples

A new dispersive liquid-liquid microextraction based on solidification of floating organic droplet method (DLLME-SFO) was developed for the determination of five kinds of polycyclic aromatic hydrocarbons (PAHs) in environmental water samples. In this method, no specific holder, such as the needle tip of microsyringe and the hollow fiber, is required for supporting the organic microdrop due to the using of organic solvent with low density and proper melting point. Furthermore, the extractant droplet can be collected easily by solidifying it in the lower temperature. 1-Dodecanol was chosen as extraction solvent in this work. A series of parameters that influence extraction were investigated systematically. Under optimal conditions, enrichment factors (EFs) for PAHs were in the range of 88-118. The limit of detections (LODs) for naphthalene, diphenyl, acenaphthene, anthracene and fluoranthene were 0.045, 0.86, 0.071, 1.1 and 0.66 ng mL⁻¹, respectively. Good reproducibility and recovery of the method were also obtained. Compared with the traditional liquid-phase microextraction (LPME) and dispersive liquid-liquid microextraction (DLLME) methods, the proposed method obtained about 2 times higher enrichment factor than those in LPME. Moreover, the solidification of floating organic solvent facilitated the phase transfer. And most importantly, it avoided using high-density and toxic solvent in the traditional DLLME method. The proposed method was successfully applied to determinate PAHs in the environmental water samples. The simple and low-cost method provides an alternative method for the analysis of non-polar compounds in complex environmental water.     

Determination of fungicides in sediments using a dispersive liquid–liquid microextraction procedure based on solidification of floating organic drop

A dispersive liquid–liquid microextraction procedure based on solidification of floating organic droplet has been investigated for the determination of fungicides (cyprodinil, difenoconazole, myclobutanil, and spiroxamine) in sediments by HPLC with diode array detection. In the overall extraction process, the extraction solvents can be separated easily from the sample solution, and the experiment time was shortened. Moreover, several parameters such as the type and volume of the extraction solvent and dispersive solvent, centrifugal speed, extraction time, and salt effect that affect the extraction efficiencies of the target fungicides were studied and optimized. Under the optimized conditions, the LOD for the target analytes were in the range of 0.1–0.5 μg/g. Satisfactory recoveries of the target analytes in the sediment samples were 81.00–99.00%, with RSDs (n = 5) that ranged from 1.8 to 6.5%. Finally, the simple, sensitive, and environmentally friendly method was successfully applied to determine the target fungicides in actual sediment samples.     

Determination of acidic drugs in biological and environmental matrices by membrane‐based dual emulsification liquid‐phase microextraction followed by high‐performance liquid chromatography

A simple method is introduced providing a highly clean microextraction for the determination of some anti‐inflammatory drugs as the model analytes in human urine and environmental matrices. This method is based upon the implementation of two consecutive emulsification liquid‐phase microextractions, which are separated by a syringe filtration step. In this method, the organic extraction solvent (dihexyl ether) is dispersed into the aqueous sample solution (20 mL), and the resulting cloudy mixture is passed through a hydrophilic polytetrafluoroethylene syringe filter. By this action, the extraction phase containing the analytes and many interfering species that could be transferred into the organic phase is retained behind the hydrophilic membrane. The filter is then detached from the syringe and attached to another syringe containing an aqueous solution (pH 12.0, 150 μL), and by the in‐syringe dispersion of the organic phase into the aqueous phase, the analytes are selectively back‐extracted into the aqueous phase. The developed method is centrifuge‐free and very simple, and provides a high sample clean‐up in a few minutes. Under the optimized experimental conditions, the developed method provided a linearity in the range of 2.0–2000 ng/mL, a low limit of detection (0.5 ng/mL), and enrichment factors of 47–53.     

In situ ionic‐liquid‐dispersive liquid–liquid microextraction of Sudan dyes from liquid samples

In situ ionic‐liquid‐dispersive liquid–liquid microextraction was introduced for extracting Sudan dyes from different liquid samples followed by detection using ultrafast liquid chromatography. The extraction and metathesis reaction can be performed simultaneously, the extraction time was shortened notably and higher enrichment factors can be obtained compared with traditional dispersive liquid–liquid microextraction. When the extraction was coupled with ultrafast liquid chromatography, a green, convenient, cheap, and efficient method for the determination of Sudan dyes was developed. The effects of various experimental factors, including type of extraction solvent, amount of 1‐hexyl‐3‐methylimidazolium chloride, ratio of ammonium hexafluorophosphate to 1‐hexyl‐3‐methylimidazolium chloride, pH value, salt concentration in sample solution, extraction time and centrifugation time were investigated and optimized for the extraction of four kinds of Sudan dyes. The limits of detection for Sudan I, II, III, and IV were 0.324, 0.299, 0.390, and 0.655 ng/mL, respectively. Recoveries obtained by analyzing the seven spiked samples were between 65.95 and 112.82%. The consumption of organic solvent (120 μL acetonitrile per sample) was very low, so it could be considered as a green analytical method.     

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.     

Determination of diflubenzuron and chlorbenzuron in fruits by combining acetonitrile‐based extraction with dispersive liquid–liquid microextraction followed by high‐performance liquid chromatography

In this study, a simple and low‐organic‐solvent‐consuming method combining an acetonitrile‐partitioning extraction procedure followed by “quick, easy, cheap, effective, rugged and safe” cleanup with ionic‐liquid‐based dispersive liquid–liquid microextraction and high‐performance liquid chromatography with diode array detection was developed for the determination of diflubenzuron and chlorbenzuron in grapes and pears. Ionic‐liquid‐based dispersive liquid–liquid microextraction was performed using the ionic liquid 1‐hexyl‐3‐methylimidazolium hexafluorophosphate as the extractive solvent and acetonitrile extract as the dispersive solvent. The main factors influencing the efficiency of the dispersive liquid–liquid microextraction were evaluated, including the extractive solvent type and volume and the dispersive solvent volume. The validation parameters indicated the suitability of the method for routine analyses of benzoylurea insecticides in a large number of samples. The relative recoveries at three spiked levels ranged between 98.6 and 109.3% with relative standard deviations of less than 5.2%. The limit of detection was 0.005 mg/kg for the two insecticides. The proposed method was successfully used for the rapid determination of diflubenzuron and chlorbenzuron residues in real fruit samples.     

Optimization of a novel method based on solidification of floating organic droplet by high-performance liquid chromatography for evaluation of antifungal drugs in biological samples

In this study, a simple, rapid, and highly efficient liquid-phase microextraction method based on solidification of floating organic droplet was coupled with high performance liquid chromatography-photo diode array detection (HPLC-PDA) for determination of ketoconazole, clotrimazole, and miconazole as antifungal drugs. Central composite design (CCD) was used for optimization of several factors affecting the extraction efficiency. The optimized conditions were established to be 550 rpm for stirring rate, 35 min for extraction time, 57 °C for extraction temperature, 8.5 for solution pH, 10 μl for organic solvent volume, and 7% (w/v) of NaCl for ionic strength. Limit of detections (LODs) of the extraction method ranged from 0.01 to 0.1 μg L⁻¹ and the linear dynamic ranges (LDRs) ranged from 0.1 to 300 μg L⁻¹ for the three antifungal drugs. Relative standard deviations (RSDs) of the proposed method were 5-11%. Preconcentration factors in the range of 306-1350 were obtained at extraction time of 35 min. Finally, performance of the proposed method was evaluated for the extraction and determination of the drugs’ levels in microgram per liter in samples and satisfactory results were obtained.     

Dispersion‐solidification liquid–liquid microextraction for volatile aromatic hydrocarbons determination: Comparison with liquid phase microextraction based on the solidification of a floating drop

Two microextraction techniques – liquid phase microextraction based on solidification of a floating organic drop (LPME‐SFO) and dispersive liquid–liquid microextraction combined with a solidification of a floating organic drop (DLLME‐SFO) – are explored for benzene, toluene, ethylbenzene and o‐xylene sampling and preconcentration. The investigation covers the effects of extraction solvent type, extraction and disperser solvents' volume, and the extraction time. For both techniques 1‐undecanol containing n‐heptane as internal standard was used as an extracting solvent. For DLLME‐SFO acetone was used as a disperser solvent. The calibration curves for both techniques and for all the analytes were linear up to 10 μg/mL, correlation coefficients were in the range 0.997–0.998, enrichment factors were from 87 for benzene to 290 for o‐xylene, detection limits were from 0.31 and 0.35 μg/L for benzene to 0.15 and 0.10 μg/L for o‐xylene for LPME‐SFO and DLLME‐SFO, respectively. Repeatabilities of the results were acceptable with RSDs up to 12%. Being comparable with LPME‐SFO in the analytical characteristics, DLLME‐SFO is superior to LPME‐SFO in the extraction time. A possibility to apply the proposed techniques for volatile aromatic hydrocarbons determination in tap water and snow was demonstrated.     

悬浮固化分散液液微萃取-高效液相色谱法测定水体中邻苯二甲酸酯

建立了悬浮固化分散液液微萃取（SFO-DLLME）结合高效液相色谱（HPLC）快速测定水样中6种邻苯二甲酸酯（PAEs）的分析方法。通过对影响萃取效率因素的优化,确定了最佳萃取条件：十二烷醇萃取剂20 μL、萃取温度60℃、离子强度20 g/L、萃取时间1 min。6种PAEs在2~2000 μg/L范围内呈良好的线性关系,相关系数（r）为0.9995~0.9999,检出限（S/N=3）为0.3~0.6 μg/L。对自来水、湖水、江水、污水、海水、市售塑料瓶装纯净水和矿泉水进行测定,能检测到部分PAEs。对加标水样进行回收率试验（10、100和1000 μg/L）,6种PAEs的回收率为84.9%~94.5%,相对标准偏差为4.1%~6.8%（n=5）。该法环保、简单,可用于实际水样中6种PAEs的检测分析。     

Syringe‐to‐syringe dispersive liquid‐phase microextraction solidified floating organic drop combined with high‐performance liquid chromatography for the separation and quantification of ochratoxin A in food samples

A new, simple, and rapid syringe‐to‐syringe dispersive liquid‐phase microextraction with solidified floating organic drop was used for the separation and preconcentration of ochratoxin A from grain and juice samples before its quantification using high‐performance liquid chromatography and fluorescence detection. Factors influencing the microextraction efficiency of ochratoxin A, such as sample solution pH, type and volume of organic extractant, salt concentration, number of injections, and volume of the sample, were studied and optimized. Under the optimum properties, the calibration graph showed linearity in the range of 65.0–700.0 ng/L (coefficient of determination = 0.9991). The limit of detection was 20.0 ng/L. The inter‐day and intra‐day relative standard deviations were in the range of 5.0–8.5%. This method was successfully applied for the quantification of ochratoxin A in grain and juice samples.     

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.     

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%.     

Ionic liquid foam floatation coupled with ionic liquid dispersive liquid–liquid microextraction for the separation and determination of estrogens in water samples by high‐performance liquid chromatography with fluorescence detection

An ionic liquid foam floatation coupled with ionic liquid dispersive liquid–liquid microextraction method was proposed for the extraction and concentration of 17‐α‐estradiol, 17‐β‐estradiol‐benzoate, and quinestrol in environmental water samples by high‐performance liquid chromatography with fluorescence detection. 1‐Hexyl‐3‐methylimidazolium tetrafluoroborate was applied as foaming agent in the foam flotation process and dispersive solvent in microextraction. The introduction of the ion‐pairing and salting‐out agent NH₄PF₆ was beneficial to the improvement of recoveries for the hydrophobic ionic liquid phase and analytes. Parameters of the proposed method including concentration of 1‐hexyl‐3‐methylimidazolium tetrafluoroborate, flow rate of carrier gas, floatation time, types and concentration of ionic liquids, salt concentration in samples, extraction time, and centrifugation time were evaluated. The recoveries were between 98 and 105% with relative standard deviations lower than 7% for lake water and well water samples. The isolation of the target compounds from the water was found to be efficient, and the enrichment factors ranged from 4445 to 4632. This developing method is free of volatile organic solvents compared with regular extraction. Based on the unique properties of ionic liquids, the application of foam floatation, and dispersive liquid–liquid microextraction was widened.     

Preconcentration and determination of ceftazidime in real samples using dispersive liquid–liquid microextraction and high‐performance liquid chromatography with the aid of experimental design

A rapid and simple method for the extraction and preconcentration of ceftazidime in aqueous samples has been developed using dispersive liquid–liquid microextraction followed by high‐performance liquid chromatography analysis. The extraction parameters, such as the volume of extraction solvent and disperser solvent, salt effect, sample volume, centrifuge rate, centrifuge time, extraction time, and temperature in the dispersive liquid–liquid microextraction process, were studied and optimized with the experimental design methods. Firstly, for the preliminary screening of the parameters the taguchi design was used and then, the fractional factorial design was used for significant factors optimization. At the optimum conditions, the calibration curves for ceftazidime indicated good linearity over the range of 0.001–10 μg/mL with correlation coefficients higher than the 0.98, and the limits of detection were 0.13 and 0.17 ng/mL, for water and urine samples, respectively. The proposed method successfully employed to determine ceftazidime in water and urine samples and good agreement between the experimental data and predictive values has been achieved.     

Single‐drop microextraction combined in‐line with capillary electrophoresis for the determination of nonsteroidal anti‐inflammatory drugs in urine samples

This study describes a method to determine nonsteroidal anti‐inflammatory drugs (NSAIDs) in urine samples based on the use of single‐drop microextraction (SDME) in a three‐phase design as a preconcentration technique coupled in‐line to capillary electrophoresis. Different parameters affecting the extraction efficiency of the SDME process were evaluated (e.g. type of extractant, volume of the microdroplet, and extraction time). The developed method was successfully applied to the analysis of human urine samples with LODs ranging between 1.0 and 2.5 μg/mL for all of the NSAIDs under study. This method shows RSD values ranging from 8.5 to 15.3% in interday analysis. The enrichment factors were calculated, resulting 27‐fold for ketoprofen, 14‐fold for diclofenac, 12‐fold for ibuprofen, and 44‐fold naproxen. Samples were analyzed applying the SDME–CE method and the obtained results presented satisfactory recovery values (82–115%). The overall method can be considered a promising approach for the analysis of NSAIDs in urine samples after minimal sample pretreatment.     

Ionic‐liquid‐based dispersive liquid–liquid microextraction for high‐throughput multiple food contaminant screening

This paper describes an innovation of dispersive liquid–liquid microextraction enabling multiple‐component analysis of eight high‐priority food contaminants in two chemically distinctive families: Sudan dyes and phthalate plasticizers. To provide convenient sample handling for solid and solid‐containing matrices, a modified dispersive liquid–liquid microextraction procedure used an extractant precoated frit to perform simultaneous filtration, solvent mixing, and phase dispersion in one simple step. A binary ionic liquid extractant system was carefully tuned to deliver high quality analysis based only on affordable LC with diode array detector instrumentation. The method is comprehensively validated for robust quantification with good precision (6.9–9.8% RSD) in a linear 2–1000 μg/L range. Having accomplished enrichment factors up to 451, the treatment enables sensitive detection at 0.09–1.01 μg/L levels. Analysis of six high‐risk solid condiments and sauces further verified its practical applicability within a 70–120% recovery range. Compared to other approaches, the current dispersive liquid–liquid microextraction treatment offers major advantages in terms of minimal solvent (1.5 mL) and sample (0.1 g) consumption, ultra‐high analytical throughput (6 min), and the ability to handle complex solid matrices. The idea of performing simultaneous analysis for multiple contaminants presented here fosters a more effective mode of operation in food control routines.     

Determination of four sulfonylurea herbicides in tea by matrix solid‐phase dispersion cleanup followed by dispersive liquid–liquid microextraction

Matrix solid‐phase dispersion combined with dispersive liquid–liquid microextraction has been developed as a new sample pretreatment method for the determination of four sulfonylurea herbicides (chlorsulfuron, bensulfuron‐methyl, chlorimuron‐ethyl, and pyrazosulfuron) in tea by high‐performance liquid chromatography with diode array detection. The extraction and cleanup by matrix solid‐phase dispersion was carried out by using CN‐silica as dispersant and carbon nanotubes as cleanup sorbent eluted with acidified dichloromethane. The eluent of matrix solid‐phase dispersion was evaporated and redissolved in 0.5 mL methanol, and used as the dispersive solvent of the following dispersive liquid–liquid microextraction procedure for further purification and enrichment of the target analytes before high‐performance liquid chromatography analysis. Under the optimum conditions, the method yielded a linear calibration curve in the concentration range from 5.0 to 10 000 ng/g for target analytes with a correlation coefficients (r²) ranging from 0.9959 to 0.9998. The limits of detection for the analytes were in the range of 1.31–2.81 ng/g. Recoveries of the four sulfonylurea herbicides at two fortification levels were between 72.8 and 110.6% with relative standard deviations lower than 6.95%. The method was successfully applied to the analysis of four sulfonylurea herbicides in several tea samples.