Traditional Dispersive Liquid-liquid Microextraction Research Articles

Novel ferrofluid based on water-based deep eutectic solvents: application in dispersive liquid-liquid microextraction of naphthalene-derived plant growth regulators in edible oil

A new ferrofluid extractant (Fe3O4 @SiO2-WDES) was ingeniously prepared by coating magnetic Fe3O4 @SiO2 microspheres with water-based deep eutectic solvent (WDES) and used for dispersive liquid-liquid microextraction (DLLME) and HPLC determination of naphthalene-derived plant growth regulators (PGRs, i.e., 1-naphthylacetic acid, 2-naphthylacetic acid, 1-naphthoxy acetic acid, 2-naphthyloxyacetic acid and 1-naphthylacetamide) in edible oil. Herein, mass transfer of the analytes in DLLME was significantly enhanced via increasing the contact surface by employing the microspheres as the supporter and dispersant of WDES, and phase separation can be efficiently achieved using an external magnet rather than centrifugation in traditional DLLME. Response surface methodology (RSM) based on Box-Behnken design (BBD) was employed for the optimization of core experimental conditions, and Analytical Eco-Scale and Analytical GREEnness Metric Approaches were adopted to evaluate the degree of greenness of the procedure. Under the optimal conditions, satisfactory performances of linearity ranged from 5 to 100 μg/L (R2 ≥ 0.9982), limit of detection (0.58–0.91 μg/L), limit of quantitation (1.9–3.0 μg/L), precision (RSDs ≤ 5.5%), recovery (81.3%−108.1%) and negligible matrix effect were achieved, which introduced a promising alternative route for the determination of naphthalene-derived plant growth regulators in edible oil.

Nanoextraction from a flow of a highly diluted solution for much-improved sensitivity in offline chemical detection and quantification

Preconcentration of the target compound is a critical step that ensures the accuracy of the subsequent chemical analysis. In this work, we present a straightforward yet effective liquid-liquid extraction approach based on surface nanodroplets (i.e., nanoextraction) for offline analysis of highly diluted sample solutions. The extraction and sample collection were streamlined in a 3-m microcapillary tube. The concentration of the target analyte in surface nanodroplets was significantly increased compared to the concentration in the sample solution, reaching several orders of magnitude. A limit of detection (LOD) was decreased by a factor of ∼103 for an organic model compound in Fourier-transform infrared spectroscopy (FTIR) measurements and ∼105 for a model fluorescent dye in fluorescence detection. The quantitative analysis of the organic compound was also achieved in a wide concentration region from 10−3 M to 10−4 M. The total volume of surface nanodroplets can be manipulated to further enhance extraction efficiency, according to the principle that governs droplet formation by solvent exchange. Additionally, our method exhibited significantly improved sensitivity compared to traditional dispersive liquid-liquid microextraction (DLLME). The LOD of the fluorescent dye and the organic model compound obtained with DLLME was 3 orders of magnitude and 20 times higher than the LOD achieved through nanoextraction approach. The nanoextraction developed in this work can be applied to preconcentrate multi-compounds from river water samples, without clear interference from each other. This can further extend its applicability for the detection and quantification of target analytes in complex aqueous samples by common analytical instruments.

A miniaturized spray-assisted fine-droplet-formation-based liquid-phase microextraction method for the simultaneous determination of fenpiclonil, nitrofen and fenoxaprop-ethyl as pesticides in soil samples.

Pesticides are a group of micropollutants that persist for a long time in the environment and pose threats to life. Much effort has been devoted to developing pre-concentration methods capable of producing samples suitable for the detection of pesticides. However, better methods are still required to detect these compounds when they are present in trace concentrations in soils. Spray-assisted fine-droplet-formation-based liquid-phase microextraction was used to prepare soil samples containing three different pesticides, fenpiclonil, nitrofen and fenoxaprop-ethyl, for subsequent analysis by gas chromatography/mass spectrometry (GC/MS). A spraying apparatus was used for the dispersion of the extraction solvent into the sample/standard solution to improve the extraction efficiency. Optimization studies were performed to lower the detection limits of these analytes and the results obtained by the application of the newly developed system were compared with those obtained using the conventional GC/MS method. A calibration curve over the range 5.0-100 μg L-1 was obtained under the optimal conditions. The limits of detection and quantification were 1.56-1.80 μg L-1 and 5.21-5.98 μg L-1 , respectively. The enhancements in detection ability over the conventional method for the three tested pesticides were 188.01, 176.96 and 517.14 for fenpiclonil, nitrofen and fenoxaprop-ethyl, respectively Recovery studies performed in soil samples were satisfactory reflecting accurate applicability of the developed method. The developed microextraction method is a time-saving and simple version of the traditional dispersive liquid-liquid microextraction method that also reduces the use of dispersive solvents.

In situ ionic liquid dispersive liquid-liquid microextraction combined with ultra high performance liquid chromatography for determination of neonicotinoid insecticides in honey samples.

An efficient in situ ionic liquid dispersive liquid-liquid microextraction followed by ultra-performance liquid chromatography was developed to determine four neonicotinoid insecticides in wild and commercial honey samples. In this method, a hydrophobic ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate, formed by in situ reaction between potassium hexafluorophosphate and 1-butyl-3-methylimidazolium bromide in sample solution, was used as the extraction solvent. In comparison with the traditional dispersive liquid-liquid microextraction method, the developed method required no dispersive solvent. To achieve high extraction efficiency and enrichment factor, the effects of various experimental parameters were studied in detail. Under the optimized conditions, the limits of detection and quantification were in the ranges of 0.30-0.62 and 1.20-2.50μg/L, respectively. The method showed high enrichment factors (74-115) with the recoveries between 81.0 and 103.4%. The proposed method was finally applied to different wild and commercial honey samples.

Inkjet-Based Dispersive Liquid-Liquid Microextraction Method Coupled with UHPLC-MS/MS for the Determination of Aflatoxins in Wheat.

A novel method was developed for determination of aflatoxin B1, B2, G1, and G2 (AFB1, AFB2, AFG1, and AFG2) in wheat using inkjet-based dispersive liquid-liquid microextraction (DLLME) coupled with ultrahigh-pressure liquid chromatography-tandem mass spectrometry. A drop-on-demand jetting device was used to form a cloudy solution in traditional DLLME by injecting extraction solvent (10 μL) as ultrafine droplets (∼20 μm diameter) at high frequency into sample solution. The method was validated using wheat as a representative matrix, which was pretreated with acetonitrile/water solution. Good linearity was observed over the studied range (0.06-6 μg/kg), and the limits of quantification (0.06-0.18 μg/kg) were below the maximum level established by the European Union for cereal. Satisfactory recoveries, ranging from 83.2% to 93.0% with relative standard deviations below 4.6%, were obtained for all compounds. The method, which is convenient and reliable and has low solvent consumption, represents a new direction for the development of traditional DLLME technology.

Comparison of three different dispersive liquid-liquid microextraction modes performed on their most usual configurations for the extraction of phenolic, neutral aromatic, and amino compounds from waters.

In this work we seek clues to select the appropriate dispersive liquid-liquid microextraction mode for extracting three categories of compounds. For this purpose, three common dispersive liquid-liquid microextraction modes were compared under optimized conditions. Traditional dispersive liquid-liquid microextraction, in situ ionic liquid dispersive liquid-liquid microextraction, and conventional ionic liquid dispersive liquid-liquid microextraction using chloroform, 1-butyl-3-methylimidazolium tetrafluoroborate, and 1-hexyl-3-methylimidazolium hexafluorophosphate as the extraction solvent, respectively, were considered in this work. Phenolic, neutral aromatic, and amino compounds (each category included six members) were studied as analytes. The analytes in the extracts were determined by high-performance liquid chromatography with UV detection. For the analytes with polar functionalities, the in situ ionic liquid dispersive liquid-liquid microextraction mode mostly led to better results. In contrast, for neutral hydrocarbons without polar functionalities, traditional dispersive liquid-liquid microextraction using chloroform produced better results. In this case, where dispersion forces were the dominant interactions in the extraction, the refractive index of solvent and analyte predicted the extraction performance better than the octanol/water partition coefficient. It was also revealed that none of the methods were successful in extracting hydrophilic analytes (compounds with the log octanol/water partition coefficient<2). The results of this study could be helpful in selecting a dispersive liquid-liquid microextraction mode for the extraction of various groups of compounds.

Development of CO2-Mediated Switchable Hydrophilicity Solvent-Based Microextraction Combined with HPLC-UV for the Determination of Bisphenols in Foods and Drinks

In traditional dispersive liquid-liquid microextraction procedures, both extraction and dispersive solvents are required, and thus, it increases the consumption of organic solvent. Herein, we reported a CO2-mediated switchable hydrophilicity solvent-based microextraction (SHS-BME) for the determination of bisphenol compounds (BPCs) in complex milk and drink samples. N,N-Dimethylcyclohexylamine was used as a switchable hydrophilicity solvent; it can switch reversibly between one form that is miscible with water and another that forms a biphasic mixture with water, and thus allow extraction of the analytes in a homogeneous phase without dispersive solvent. Several important parameters were screened and optimized by single factor experiments and central composite design as follows: 782 μL of switchable solvent, 375 μL of NaOH solvent, and 1.1:1 switchable solvent/water (v/v). Under the optimized SHS-BME conditions, the limit of detections (LODs) for BPCs in milk, orange juice, and energy drink samples were in the range of 0.27–0.40 μg L−1 for BPE, 0.17–0.30 μg L−1 for BPA, and 0.50–0.67 μg L−1 for BPB, respectively, and the extraction recoveries for BPCs were in the range of 79.5–103.4% in milk, of 84.5–97.5% in orange juice, and of 91.9–101.2% in energy drinks. The precision of the method, based on relative standard deviations (RSDs), ranged from 1.7 to 4.8% and from 2.1 to 5.7% for intra-day and inter-day comparisons, respectively. In total, this SHS-BME method possesses many advantages, such as high extraction recovery and high detection sensitivity (low LODs and RSDs), no requirement of dispersive solvent, simple operational procedure, reducing the pretreatment time and workload, and so on. Therefore, it has a great potential application value for detection of trace BPCs in routine food tests.

Determination of Sudan Dyes in Juice Samples via Solidification of Ionic Liquid in Microwave-Assisted Liquid-Liquid Microextraction Followed by High-Performance Liquid Chromatography

Solidification of ionic liquid (SIL) has been applied in microwave-assisted liquid-liquid microextraction method for analyzing Sudan dyes in juice samples. 1-Ethy-3-methylimidazolium hexafluorophosphate ([C2MIM][PF6]) was selected as the extraction solvent due to its relatively high melting point. With the aid of microwave irradiation, the dyes could be easily extracted into ionic liquid phase without dispersive solvent. The solid microdroplet could be easily separated from liquid. Compared with traditional dispersive liquid-liquid microextraction, this method will greatly simplify the collection procedure and shorten the operation time. Several experimental parameters, including the amount of ionic liquid, microwave power and irradiation time, pH of sample solution, and ionic strength, were systematically investigated and optimized. The limits of detection for Sudan I, II, III, and IV were 1.08, 1.30, 1.14, and 1.19 μg/L, respectively. The recoveries of the analytes ranged from 83.42 to 115.56 % and relative standard deviations were lower than 11.53 %, when the present method was applied to the analysis of real samples.

Dispersive Liquid–Liquid Microextraction Using Low-Toxic Solvent for the Determination of Heavy Metals in Water Samples by Inductively Coupled Plasma–Mass Spectrometry

A low-toxic dispersive liquid-liquid microextraction (DLLME) combined with inductively coupled plasma-MS was used for preconcentration and determination of Cu, Cr, Cd, Ni, Mn, and Pb in real-water samples. In traditional DLLME analysis, chlorinated solvents have been widely used as extraction solvents. However, these solvents are not environmentally friendly. To overcome this problem, we used a low-toxic bromosolvent (1-bromo-3-methylbutane; lethal concentration, 50%, 6150 mg/kg) as the extraction solvent. To study the effects of different parameters on the extraction efficiency, an orthogonal array experimental design with an L16(4(5)) matrix was used. Under the best experimental conditions (i.e., concentration of complexing reagent 1-(2-pyridylazo)-2-naphthol, 1.5 × 10(-3) mol/L; pH, 7.0; volume of acetone, 0.5 mL; volume of 1-bromo-3 methylbutane, 30 μL; and without salt addition), the enhancement factor ranged from 34 to 40. The linear dynamic range was 1-1000 μg/L with r(2) values of 0.9984-0.9999, and the LODs were between 0.042 and 0.53 μg/L. RSDs (at metal ion concentrations of 20 μg/L, n = 6) were 2.12 to 3.42%. The developed method was successfully applied to the extraction and determination of the mentioned metal ions in real-water samples, and satisfactory results were obtained.

Sensitive determination of methadone in human serum and urine by dispersive liquid-liquid microextraction based on the solidification of a floating organic droplet followed by HPLC-UV.

Dispersive liquid-liquid microextraction based on solidification of floating organic droplet was developed for the extraction of methadone and determination by high-performance liquid chromatography with UV detection. In this method, no microsyringe or fiber is required to support the organic microdrop due to the usage of an organic solvent with a low density and appropriate melting point. Furthermore, the extractant droplet can be collected easily by solidifying it at low temperature. 1-Undecanol and methanol were chosen as extraction and disperser solvents, respectively. Parameters that influence extraction efficiency, i.e. volumes of extracting and dispersing solvents, pH, and salt effect, were optimized by using response surface methodology. Under optimal conditions, enrichment factor for methadone was 134 and 160 in serum and urine samples, respectively. The limit of detection was 3.34ng/mmL in serum and 1.67ng/mL in urine samples. Compared with the traditional dispersive liquid-liquid microextraction, the proposed method obtained lower limit of detection. Moreover, the solidification of floating organic solvent facilitated the phase transfer. And most importantly, it avoided using high-density and toxic solvents of traditional dispersive liquid-liquid microextraction method. The proposed method was successfully applied to the determination of methadone in serum and urine samples of an addicted individual under methadone therapy.

Dispersive Liquid-Liquid Microextraction with Liquid Chromatography-Tandem Mass Spectrometry for the Determination of Triazine, Neonicotinoid, Triazole and Imidazolinone Pesticides in Mineral Water Samples

Mineral water is known for its high purity. Because mineral water is produced by the infiltration of water through the soil, there is the possibility of contamination with pesticides. The aim of this study was to develop a simple, rapid and efficient method for the extraction and preconcentration of different classes of pesticides in mineral water samples by dispersive liquid-liquid microextraction (DLLME) coupled with liquid chromatography tandem mass spectrometry. To optimize the DLLME conditions for the different classes of pesticides and access the effect of variables on the extraction, a central composite design (CCD) with a five-level fractional factorial design was used for the construction of a second order response surface model (RSM). The limits of quantification were between 0.005 and 0.5 μg L-1. Correlation coefficients (r) were higher than 0.999. Recoveries ranged from 102 to 120%, with relative standard deviations between 1 and 10%. Low matrix effect for all compounds was observed. The result showed that using a mixture of acetone and acetonitrile as disperser solvent and a mixture of chloroform and monochlorobenzene as extractor solvent, it is possible to employ the traditional DLLME with chlorinated solvents to extract the multiclass pesticides from the water samples.

In situionic-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.

Novel coupling of surfactant assisted emulsification dispersive liquid–liquid microextraction with spectrophotometric determination for ultra trace nickel

In this work, dispersive liquid–liquid microextraction (DLLME) was improved and the preconcentration method named as surfactant assisted emulsification dispersive liquid–liquid microextraction (SAE-DLLME) was established for ultra trace nickel preconcentration and spectrophotometric determination. Non-ionic surfactant Triton X-100 (TX-100) was used as emulsifier and Triton X-114 (TX-114) was investigated as comparison. Disperser solvent was substituted by surfactant, which could afford more effective emulsification and make the extraction relatively greener. The extraction was accomplished efficiently in only 1min during manual shaking. Compared to traditional DLLME, the developed SAE-DLLME pretreatment was simple, rapid and effective. The improved extraction technique was firstly coupled with traditional spectrophotometer to improve the analytical performance and expand the application of spectrophotometric determination. The influence factors relevant to SAE-DLLME including extraction parameters and instrumental conditions, were studied in detail. Under the optimal conditions, the limit of detection (LOD) for nickel was 0.24μgL−1, with sensitivity enhancement factor (EF) of 23.

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.