Countercurrent Salting-out Homogenous Liquid-Liquid Extraction and Dispersive Liquid-Liquid Microextraction Based on the Solidification of Floating Organic Drop Followed by High-Performance Liquid Chromatography for the Isolation and Preconcentration of P
Pesticides are widely used to control pests and prevent diseases in crops, including cereals, vegetables, and fruits. Due to factors such as the persistence of pesticides, bioaccumulation, and potential toxicity, pesticide residue monitoring in foodstuffs is very important.
In the current research, we proposed a novel approach using countercurrent salting-out homogenous liquid-liquid extraction combined with dispersive liquid-liquid microextraction based on the solidification of floating organic droplets (DLLME-SFO) for isolation and preconcentration of pesticides from aqueous samples for analysis by high-performance liquid chromatography-ultraviolet detection (HPLC-UV).
In brief, sodium chloride was used as a separation reagent, in a small glass column, through which was passed a mixture of an aqueous solution of, for example, fruit juice and acetonitrile. In this process, the droplets rose through the column and a separated layer would be formed on the remained an aqueous phase. Following that, acetonitrile as the organic phase was mixed with 50.0 µL of 1-undecanol (extraction solvent). To further enrich the analytes, the mixture was injected into 5 mL of a 4% w/v sodium chloride solution and placed in a tube for the DLLME-SFO.
Under optimal conditions, a dynamic linear range of 0.5-500 μg/L, extraction recovery of 65-85%, enrichment factors of 108-142, and limit of detection of 0.2-0.4 μg/L were obtained for the organophosphorus pesticides analysed. In addition, the repeatability and reproducibility from five replicate measurements of the pesticides (100 μg/L) were within the ranges of 3.5-5.1% and 4.5-6.3%, respectively .
In this research, a new extraction method based on countercurrent salting out homogeneous liquid-liquid extraction combined with DLLME-SFO has been applied for the determination of pesticide residues in fruits, juice and environmental samples before using HPLC-UV analysis. The combined method not only leads to high enrichment factors, but can also be used in complex matrices (such as fruits, juices and high-salt solutions) without pre-treatment or dilution. Compared with other sample preparation methods, this analysis procedure has many advantages, including simplicity, ease of operation, high pre-enrichment factor, low detection limit and relatively short analysis time.
Combination of CCSHLLE and DLLME-SFO was applied for the analysis of organophosphorous pesticide residues in fruit, fruit juices and environmental samples. The DLLME-SFO method avoided using high density and toxic extraction solvents. LODs are achievable at ng L-1 using CCSLLE-DLLME-SFO-HPLC-UV.
Teymori Z
，Sadeghi M
，Fattahi N
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Ultrasound-assisted surfactant-enhanced emulsification microextraction based on the solidification of a floating organic droplet used for the simultaneous determination of six fungicide residues in juices and red wine.
A novel ultrasound-assisted surfactant-enhanced emulsification microextraction technique based on the solidification of a floating organic droplet followed by high performance liquid chromatography with diode array detection was developed for simultaneous determination of six fungicide residues in juices and red wine samples. The low-toxicity solvent, 1-dodecanol, was used as an extraction solvent. For its low density and proper melting point near room temperature, the extractant droplet was collected easily by solidifying it at a low temperature. The surfactant, Tween 80, was used as an emulsifier to enhance the dispersion of the water-immiscible extraction solvent into an aqueous phase, which hastened the mass-transfer of the analytes. Organic dispersive solvent typically required in common dispersive liquid-liquid microextraction methods was not used in the proposed method. Some parameters (e.g., the type and volume of extraction solvent, the type and concentration of surfactant, ultrasound extraction time, salt addition, and volume of samples) that affect the extraction efficiency were optimized. The proposed method showed a good linearity within the range of 5μgL(-1)-1000μgL(-1), with the correlation coefficients (γ) higher than 0.9969. The limits of detection for the method ranged from 0.4μgL(-1) to 1.4μgL(-1). Further, this simple, practical, sensitive, and environmentally friendly method was successfully applied to determine the target fungicides in juice and red wine samples. The recoveries of the target fungicides in red wine and fruit juice samples were 79.5%-113.4%, with relative standard deviations that ranged from 0.4% to 12.3%.
You X
，Wang S
，Liu F
，Shi K
... -
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Green aspects, developments and perspectives of liquid phase microextraction techniques.
Determination of analytes at trace levels in complex samples (e.g. biological or contaminated water or soils) are often required for the environmental assessment and monitoring as well as for scientific research in the field of environmental pollution. A limited number of analytical techniques are sensitive enough for the direct determination of trace components in samples and, because of that, a preliminary step of the analyte isolation/enrichment prior to analysis is required in many cases. In this work the newest trends and innovations in liquid phase microextraction, like: single-drop microextraction (SDME), hollow fiber liquid-phase microextraction (HF-LPME), and dispersive liquid-liquid microextraction (DLLME) have been discussed, including their critical evaluation and possible application in analytical practice. The described modifications of extraction techniques deal with system miniaturization and/or automation, the use of ultrasound and physical agitation, and electrochemical methods. Particular attention was given to pro-ecological aspects therefore the possible use of novel, non-toxic extracting agents, inter alia, ionic liquids, coacervates, surfactant solutions and reverse micelles in the liquid phase microextraction techniques has been evaluated in depth. Also, new methodological solutions and the related instruments and devices for the efficient liquid phase micoextraction of analytes, which have found application at the stage of procedure prior to chromatographic determination, are presented.
Spietelun A
，Marcinkowski Ł
，de la Guardia M
，Namieśnik J
... -
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Ionic liquid-assisted liquid-phase microextraction based on the solidification of floating organic droplets combined with high performance liquid chromatography for the determination of benzoylurea insecticide in fruit juice.
A green, simple, and efficient method, ionic liquid-assisted liquid-liquid microextraction based on the solidification of floating organic droplets (ILSFOD-LLME) collected via a bell-shaped collection device (BSCD) coupled to high performance liquid chromatography with a variable-wavelength detector, was developed for the preconcentration and analysis of seven benzoylurea insecticides (BUs) in fruit juice. In the proposed method, the low-density solvent 1-dodecanol and the ionic liquid trihexyl(tetradecyl)phosphonium hexafluorophosphate ([P14, 6, 6, 6]PF6) were used as extractant. The extraction solvent droplet was easily collected and separated by the BSCD without centrifugation. The experimental parameters were optimized by the one-factor-at-a-time approach and were followed using an orthogonal array design. The results indicated the different effects of each parameter for extraction efficiency. Under the optimal conditions in the water model, the limits of detection for the analytes varied from 0.03 to 0.28μgL(-1). The enrichment factors ranged from 160 to 246. Linearities were achieved for hexaflumuron and flufenoxuron in the range of 0.5-500μgL(-1), for triflumuron, lufenuron and diafenthiuron in the range of 1-500μgL(-1), and for diflubenzuron and chlorfluazuron in the range of 5-500μgL(-1); the correlation coefficients for the BUs ranged from 0.9960 to 0.9990 with recoveries of 75.6-113.9%. Finally, the developed technique was successfully applied to real fruit juice with acceptable results. The relative standard deviations (RSDs) of the seven BUs at two spiked levels (50 and 200μgL(-1)) varied between 0.1% and 7.3%.
Yang M
，Zhang P
，Hu L
，Lu R
，Zhou W
，Zhang S
，Gao H
... -
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