Dispersive Liquid-liquid Microextraction Based On Solidification Of Floating Organic Droplet Research Articles

Analysis of six preservatives in beverages using hydrophilic deep eutectic solvent as disperser in dispersive liquid-liquid microextraction based on the solidification of floating organic droplet

In this work, a deep eutectic solvent (DES) composed of tetrabutylammonium bromide (TBABr) and acetic acid in a 1:2 M ratio was applied as the dispersive solvent for the dispersive liquid-liquid microextraction based on solidification of floating organic droplet (DLLME-SFO), using 1-decanol as extractant. Six preservatives (benzoic acid, BA; sorbic acid, SA; methyl paraben, MP; ethyl paraben, EP; propyl paraben PP; and butyl paraben, BP) in beverages were determined simultaneously through high-performance liquid chromatography with a diode array detector (HPLC-DAD). Under the optimal experimental condition that consists of 200 μL of disperser (TBABr: acetic acid, 1:2), 80 μL of extractant (1-decanol), 3 min of vortex time, 4.5 of pH, 2.5 g of NaCl, the proposed method showed satisfactory linearity in the range of 0.05−50.0 mg L−1, with a correlation coefficient (R2) higher than 0.9998. The limits of detection (LODs) varied from 0.02 to 0.05 mg L-1 and the limits of quantification (LOQs) varied from 0.05−0.1 mg L−1. The relative standard deviations (intra-day and inter-days) were below 5 %. The developed method was successfully applied to the determination of preservatives in beverages.

Simultaneous determination of polycyclic aromatic hydrocarbons and phthalate esters in surface water by dispersive liquid-liquid microextraction based on solidification of floating organic drop followed by high performance liquid chromatography

Polycyclic aromatic hydrocarbons (PAHs) and phthalate esters (PAEs) are internationally recognized as priority pollutants; hence, it is important to monitor their concentrations in the environment. However, the low concentrations of PAHs and PAEs in surface water make the direct and sensitive determination of these compounds by instrumental methods difficult. Therefore, the development of an accurate and rapid sample pretreating method for the determination of PAHs and PAEs in water has always been the goal of environmental scientists. Dispersive liquid-liquid microextraction based on solidification of floating organic droplet (DLLME-SFO) is a simple, rapid, low-cost, sensitive, and environmentally friendly method. Methods based on DLLME-SFO for the simultaneous determination of PAHs and PAEs in surface water have rarely been reported. In this study, a novel DLLME-SFO method was developed for the simultaneous determination of 16 PAHs and 6 PAEs in surface water samples. To optimize the extraction efficiency for the target compounds, various parameters, including the types and volumes of extractants and dispersants, ionic strength, and extraction time, were investigated. First, 1-undecanol (melting point:19℃) and 1-dodecanol (melting point:24℃) were selected as extractive solvents, and their extraction efficiency was investigated. The results showed that 1-dodecanol had better extraction efficiency. The melting point of 1-undecanol was relatively low, and the droplets that solidified during the experiment were easy to melt and break, which led to the low recovery rate of extraction. Then, the effect of the volume (10, 20, 30, 40, 50 μL) of 1-dodecanol was investigated, and the extraction efficiency of the target compounds was found to decrease with increasing volume of 1-dodecanol. Second, the effect of four dispersive solvents (methanol, ethanol, acetonitrile, and acetone) on the extraction efficiencies was studied. The extraction efficiencies of the target compounds were the highest when methanol was used as the dispersant; hence, the effect of different volumes of methanol on the extraction efficiency was further examined. When the volume of methanol was less than 500 μL, the contact area between the extraction solvent and the water phase increased with increasing methanol volume, and the extraction efficiency increased. However, when the volume of methanol was more than 500 μL, the excessive dispersant increased the solubility of the target compound in the water phase, which led to a decrease in the extraction efficiency. Finally, the effects of salt addition and vortex oscillation time on the extraction efficiency were probed. The experimental results indicated that the extraction efficiency increased with an increase in the quantity of NaCl. When the NaCl quantity was greater than 0.2 g, there was no notable change in the extraction efficiency. Vortex oscillation could accelerate the establishment of the extraction equilibrium, and the extraction efficiency reached a stable state when the vortex oscillation time was more than 2 min. According to the abovementioned results, the optimized DLLME-SFO conditions were established as follows:for 5.0 mL water samples, 10 μL of 1-dodecanol was chosen as the extraction solvent, 500 μL of methanol was used as the dispersive solvent, the vortex oscillation extraction time was 2 min, and the NaCl quantity was 0.2 g. The target compounds were analyzed by high-performance liquid chromatography. Separation of the PAHs and PAEs was achieved on a SUPELCOSILTM LC-PAH column (150 mm×4.6 mm, 5 μm) with acetonitrile-water as the mobile phase using a gradient elution program. Fifteen PAHs were detected using a fluorescence detector, and six PAEs and acenaphthylene were detected by an ultraviolet detector. Quantitative determination was achieved by the external standard method. This method was successfully validated for the analyses of the 16 PAHs and 6 PAEs in two types of water samples (tap water and river water). The average recoveries of the target compounds were 60.2%-113.5%, and the corresponding relative standard deviations (RSDs, n=3) were 1.9%-14.3%. The limits of detection (LODs, S/N=3) ranged from 0.002 μg/L to 0.07 μg/L for the PAHs and from 0.2 μg/L to 2.2 μg/L for the PAEs. The limits of quantification (LOQs, S/N=10) ranged from 0.006 μg/L to 0.23 μg/L for the PAHs and from 0.8 μg/L to 7.4 μg/L for PAEs. The proposed method is simple, fast, low-cost, and environmentally friendly, and it is suitable for the rapid determination of trace PAHs and PAEs in surface water samples.

Analysis of Organic Components by DLLME Based on the Solidification of a Floating Organic Droplet Followed with GC/MS in Wood Vinegar

A simple, efficient and environmentally friendly method has been established for the analysis of organic components in wood vinegar (WV) by dispersive liquid-liquid micro-extraction based on solidification of floating organic droplet (DLLME-SFO) coupled with GC/MS. Several variables that affect the extraction efficiency, including the type and volume of the extractant and dispersant, extraction time and the mass fraction of sodium chloride were optimized. Under the optimum conditions, the sample extracted were analyzed by GC/MS. The result shows that, apart from the main component of acetic acid, many kinds of ketone compound, phenol compound, ester compound, aldehyde and alcohol compound exist in the WV. The proposed method has been successfully employed to determine the organic components in the WV.

Analysis of organophosphorus and pyrethroid pesticides in organic and conventional vegetables using QuEChERS combined with dispersive liquid-liquid microextraction based on the solidification of floating organic droplet

A simple, sensitive and environmentally-friendly method for determining organophosphorus and pyrethroid pesticides in vegetables was developed to better evaluate the risk of consuming them. The pesticides in vegetables were extracted, purified and concentrated by using the QuEChERS (quick, easy, cheap, effective, rugged and safe method) combined DLLME-SFO (dispersive liquid–liquid microextraction based on solidification of floating organic droplet) techniques. The key parameters were optimized through orthogonal array experimental design and statistical analysis. The linearity of the calibration curves was satisfied in matrix-matched standard solution with R2 ≥ 0.99. The limits of detection and limits of quantification were 0.3–1.5 and 0.9–4.7 μg/kg, respectively. The average recoveries of pesticides were 61.6–119.4% with relative standard deviations <16.1%. Furthermore, the method was applied successfully to analyse the pesticides in 15 pairs of organic and conventional vegetables. These results reflect the efficiency, reliability and robustness of the developed method.

Determination of Budesonide and Sulfasalazine in Water and Wastewater Samples Using DLLME-SFO-HPLC-UV Method

Dispersive liquid–liquid microextraction based on solidification of floating organic droplet (DLLME-SFO) was applied to isolate budesonide (BUD) and sulfasalazine (SULF) from aqueous samples. The effects of different parameters on the efficiency on the extraction such as type of extrahent and dispersive solvent, ionic strength, pH of sample, and centrifugation time were investigated. Moreover, the influence of foreign substances on a studied process was tested. The calibration curves were recorded. The linearity ranges for BUD and SULF were 0.022–8.611 µg mL−1 and 0.020–7.968 µg mL−1 with the limit of detection (LOD) 0.011 µg mL−1 and 0.012 µg mL−1, respectively. The enrichment factors (EF) for two analytes were high: for BUD it was 145.7 and for SULF, 119.5. The elaborated procedure was applied for HPLC-UV determination of these analytes in water and wastewater samples.

Deep eutectic solvent as a novel disperser in dispersive liquid-liquid microextraction based on solidification of floating organic droplet (DLLME-SFOD) for preconcentration of steroids in water samples: Assessment of the method deleterious impact on the environment using Analytical Eco-Scale and Green Analytical Procedure Index

Herein, we seek clues to investigate the effectiveness of deep eutectic solvent (DES) as a novel dispersive solvent in DLLME-SFOD for the enrichment of nine steroids in water for the first time. The novel DLLME-SFOD method is premised on using 2-dodecanol as extractant and DES (tetrabutylammonium bromide: acetic acid) as a dispersive solvent. Using DES as disperser was compared with other conventional dispersers like (ethanol, methanol, and acetone) attaining a higher recovery than the conventional dispersers. Both HPLC-DAD separation and DLLME-SFOD procedure were optimized by one-factor-at-a-time (OFAT) succeeded by experimental design applying response surface methodology (RSM) to check the optimal conditions of both HPLC separation and extraction. Under the optimal conditions, the proposed method revealed good linearity (correlation coefficients ≥0.998), low detection limits (in the range of 1.0–9.7 ng/mL), and high inter- and intra-day precision (%RSD <5) with high preconcentration factors in the ranges of (44–112) for the nine concerned steroids. Moreover, the method was successfully applied to determine the concerned steroids in different real aqueous samples with expanded measurement uncertainty of the results <17% at 95% confidence level. Finally, the developed procedure impact on the environment was assessed by applying the Analytical Eco-Scale and Green Analytical Procedure Index (GAPI) tools, proving the greenness of the method. The novel disperser DESs have the merits of simple preparation, low cost, enhancing extraction efficiency and being eco-friendly. These DESs can be used to replace conventional organic disperser solvents.

Solid-Phase Extraction Combined with Dispersive Liquid-Liquid Microextraction Based on Solidification of Floating Organic Droplet for Simultaneous Determination of Organochlorine Pesticides and Polychlorinated Biphenyls in Fish

Solid-phase extraction (SPE) was combined with dispersive liquid-liquid microextraction based on solidification of floating organic droplet (DLLME-SFO) as a pretreatment technique for the simultaneous analysis of 11 organochlorine pesticides (OCPs) and 5 polychlorinated biphenyls (PCBs) in fish tissue. Gas chromatography with electron capture detector was used for the identification and quantification of these compounds. In the newly developed method, the acetonitrile extractant of the fish sample was cleaned up by commercialized SPE cartridges packed with acid alumina, and then mixed with water, sodium-chloride, and n-pentadecane for the purpose of target analyte enrichment via DLLME-SFO process. Effect of the parameters including SPE packing material, amount and chemical nature of extraction solvent, water volume, and salt concentration on the signal responses were investigated, and the recoveries of this method ranged between 70.1% and 112.3% at three spiked levels under the optimized conditions. The calibration curves were found to be linear in the range of 1.56–312.5 μg L−1, and the limits of detection ranged from 0.372 to 1.12 μg kg−1. Comparing the other reported pretreatment method, the presented one was sensitive, time-saving, and environmentally friendly.

Dispersive Liquid-Liquid Microextraction Based on Solidification of Floating Organic Drop Combined with High Performance Liquid Chromatography for Analysis of 15 Phthalates in Water.

Background: Consistent toxicological evidence indicate that phthalates can cause adverse effects on human health. The concern over phthalate pollution and exposure has been emphasized in recent years. Therefore, the sensitive, reliable, and rapid detection of phthalates in water is of great importance. Objective: In this study, dispersive liquid-liquid microextraction based on solidification of floating organic droplet (DLLME-SFO) combined with HPLC-UV detection was established and applied in the preconcentration and detection of 15 phthalates in drinking and river water samples. Methods: A mixture of acetonitrile (dispersant) and 1-dodecanol (extractant) was injected into water samples, which had been added with sodium chloride. The cloudy solution was formed by hand-shaking. After centrifugation, the sample solution was cooled in a refrigerator, and the solidified organic droplet was collected. It melted at room temperature and was injected into the HPLC system for analysis. The quantification was based on the working curves. Results: Under optimum conditions, this method showed good linearity in the range of 0.1-100 or 0.5-100 μg/L with correlation coefficients greater than 0.999. The method had the LODs ranging from 0.013 to 0.16 μg/L with the enrichment factors of 102-218. The recoveries of the method ranged from 86.8 to 119% with RSDs less than 12.6%. The interday and intraday RSDs were 6.35-13.5% and 3.00-13.7%, respectively. The established method has been successfully applied to the analysis of phthalates in drinking and river waters. Conclusions: The established method is rapid, sensitive, cost-effective, and environmentally friendly. It can be applied to the analysis of 15 phthalates in drinking and river water samples. Highlights: A method of DLLME-SFO combined with HPLC-UV detection has been established for the analysis of 15 phthalates in drinking and river water samples. The established method was rapid, sensitive, accurate, cost-effective, and environmentally friendly. The established method was successfully applied to the analysis of 15 phthalates in bottled, tap, and river water samples.

Dispersive-Solid-Phase Extraction Cleanup Integrated to Dispersive Liquid-Liquid Microextraction Based on Solidification of Floating Organic Droplet for Determination of Organochlorine Pesticides in Vegetables

A simple and rapid method applying acetonitrile extraction, dispersive-solid-phase extraction (d-SPE) cleanup, and dispersive liquid-liquid microextraction based on solidification of floating organic droplet (DLLME-SFO) was developed for determination of organochlorine pesticides in vegetables. In order to simplify operation, d-SPE cleanup was integrated to DLLME-SFO concentration procedure, and a protection device for glass tube was applied to achieving high-speed centrifugation. The comparison study between the integrated d-SPE and normal d-SPE showed that the former could shorten the sample preparation time without decrease of cleanup efficiency. Subsequently, the necessity of using a high-centrifugation speed (more than 8603 g) for complete separation of the d-SPE sorbents, water phase, and organic phase was confirmed through turbidity analysis. The recoveries of the proposed method ranged from 77.2 to 112.5%, and the relative standard deviations were less than 15%. The limits of detection were in the range of 0.45 ~ 1.33 μg kg−1, while the limits of quantitation were from 1.35 to 3.99 μg kg−1, respectively. Finally, the method was successfully applied to analyze real vegetable samples.

Comparison of two microextraction methods based on solidification of floating organic droplet for the determination of multiclass analytes in river water samples by liquid chromatography tandem mass spectrometry using Central Composite Design

Two low density organic solvents based liquid–liquid microextraction methods, namely Vortex assisted liquid–liquid microextraction based on solidification of floating organic droplet (VALLME-SFO) and Dispersive liquid–liquid microextraction based on solidification of floating organic droplet(DLLME-SFO) have been compared for the determination of multiclass analytes (pesticides, plasticizers, pharmaceuticals and personal care products) in river water samples by using liquid chromatography tandem mass spectrometry (LC–MS/MS). The effect of various experimental parameters on the efficiency of the two methods and their optimum values were studied with the aid of Central Composite Design (CCD) and Response Surface Methodology(RSM). Under optimal conditions, VALLME-SFO was validated in terms of limit of detection, limit of quantification, dynamic linearity range, determination of coefficient, enrichment factor and extraction recovery for which the respective values were (0.011–0.219ngmL−1), (0.035–0.723ngmL−1), (0.050–0.500ngmL−1), (R2=0.992–0.999), (40–56), (80–106%). However, when the DLLME-SFO method was validated under optimal conditions, the range of values of limit of detection, limit of quantification, dynamic linearity range, determination of coefficient, enrichment factor and extraction recovery were (0.025–0.377ngmL−1), (0.083–1.256ngmL−1), (0.100–1.000ngmL−1), (R2=0.990–0.999), (35–49), (69–98%) respectively. Interday and intraday precisions were calculated as percent relative standard deviation (%RSD) and the values were ≤15% for VALLME-SFO and DLLME-SFO methods. Both methods were successfully applied for determining multiclass analytes in river water samples.

Chromatographic Methods for Analysis of Triazine Herbicides

Gas chromatography (GC) and high-performance liquid chromatography (HPLC) coupled to different detectors, and in combination with different sample extraction methods, are most widely used for analysis of triazine herbicides in different environmental samples. Nowadays, many variations and modifications of extraction and sample preparation methods such as solid-phase microextraction (SPME), hollow fiber-liquid phase microextraction (HF-LPME), stir bar sportive extraction (SBSE), headspace-solid phase microextraction (HS-SPME), dispersive liquid-liquid microextraction (DLLME), dispersive liquid-liquid microextraction based on solidification of floating organic droplet (DLLME-SFO), ultrasound-assisted emulsification microextraction (USAEME), and others have been introduced and developed to obtain sensitive and accurate methods for the analysis of these hazardous compounds. In this review, several analytical properties such as linearity, sensitivity, repeatability, and accuracy for each developed method are discussed, and excellent results were obtained for the most of developed methods combined with GC and HPLC techniques for the analysis of triazine herbicides. This review gives an overview of recent publications of the application of GC and HPLC for analysis of triazine herbicides residues in various samples.

Improved dispersive liquid–liquid microextraction based on the solidification of floating organic droplet method with a binary mixed solvent applied for determination of nicotine and cotinine in urine

A fast, simple and environmentally friendly method to determine nicotine and cotinine in urine has been developed using dispersive liquid–liquid microextraction based on solidification of floating organic droplet (DLLME-SFO) with a binary mixed extractant as the pretreatment method and high performance liquid chromatography with an ultraviolet detector (HPLC-UVD) as the analysis system. The nicotine and cotinine in urine samples were extracted using the binary mixed solvent of undecanol and CHCl3 (v/v = 1 : 1) during the DLLME-SFO procedure. The employment of the mixed solvent had significantly improved the extraction efficiency of cotinine. Several crucial experiment parameters were evaluated, including the type and volume of extract solvent, type of dispersive solvent, pH of the aqueous phase, concentration of sodium chloride in the urine samples and extraction time. Under the optimal conditions, good linearity was observed in the range of 0.01–5.00 μg mL−1 for nicotine and cotinine with correlation coefficients of 0.9993 and 0.9996 respectively, and the method detection limit (MLD) was 0.002 μg mL−1 for both analytes. The proposed method was applied to urine sample analysis and the spiked recoveries of nicotine and cotinine were in the range of 78.0–105.0% and 72.0–86.7% respectively, with the relative standard deviations (RSDs) in the range of 6.02–7.28% and 2.94–8.43% respectively.

Derivatization and Solidification of Floating Dispersive Liquid‐phase Microextraction for the Analysis of Kanamycin in Wastewater and Soil by HPLC with Fluorescence Detection

The abuse and uncontrolled discharge of kanamycin may result in potential risks to human health through food chain or environmental residues. Hence, the determination of kanamycin in various matrices is necessary. A sensitive and simple dispersive liquid–liquid microextraction based on solidification of floating organic droplet (DLLME‐SFO) method has been developed for monitoring kanamycin in environmental samples. The method of DLLME‐SFO after derivatization is coupled with high performance LC with fluorescence detection. The comparison was carried out between the staged and one‐step procedure. The results indicated that the fluorescence derivatization reaction with 9‐fluorenylmethyl chloroformate should be performed prior to extraction. The derivatization and DLLME‐SFO conditions were optimized, respectively. Under the optimal conditions, the proposed method presented good linearity with square correlation coefficient of 0.9934, good reproducibility with relative standard deviations less than 9.6%, and the recoveries of kanamycin ranged from 91.3 to 102.7% for wastewater, and from 90.3 to 107.7% for soil. Furthermore, the detection limit was observed as 0.012 ng/mL. The proposed method was successfully applied to determine low levels of kanamycin in wastewater and soil samples.

Analysis of amino acids in tobacco by derivatization and dispersive liquid–liquid microextraction based on solidification of floating organic droplet method

A new one-step derivatization and microextraction technique was developed for determination of amino acids in tobacco samples. In the proposed method, amino acids were derivatized with isobutyl chloroformate (IBCF) in aqueous solution. The derivatives were extracted by dispersive liquid–liquid microextraction based on solidification of floating organic droplet (DLLME-SFO). Parameters affecting the extraction efficiency were investigated in detail. The optimum conditions were as follows: a mixture of 500μL acetone, containing 40μL 2-dodecanol, was rapidly injected by syringe into the 2mL water sample. After centrifugation, the 2-dodecanol droplets were floated at the top of the tube. Then, the tube was cooled in an ice bath. After 5min the solvent had solidified and was then transferred into a conical vial; it melted quickly at room temperature and it was injected into a gas chromatograph for analysis. Under the optimum conditions, the limits of detection were of the order of 0.12–2.82μg/mL. The calibration curves showed good linearity over the investigated concentration range between 0.5 and 200μg/mL with a coefficient of estimation (R2)>0.9887 for GC–MS (SIM). The proposed method is an alternative approach to the quantification of amino acids in tobacco samples.

Application of Dispersive Liquid-Liquid Microextraction Based on Solidification of Floating Organic Droplet Multi-residue Method for the Simultaneous Determination of Polychlorinated Biphenyls, Organochlorine, and Pyrethroid Pesticides in Aqueous Sample

Dispersive liquid–liquid microextraction based on solidification of floating organic droplet (DLLME-SFO) technique was successfully applied for simultaneous assay of eight polychlorinated biphenyls, two organochlorine, and four pyrethroid pesticides multi-residue in aqueous samples by using GC-electron capture detection. The effects of various parameters such as kind of extractant and dispersant and volume of them, extraction time, effect of salt addition, and pH were optimized. As a result, 5.0 µL 1-dodecanol was chosen as extraction solvent, 600 µL methanol were used as dispersive solvent without salt addition, pH was adjusted to 7. Under the optimized conditions, the limits of detection (LOD) were ranged from 1.4 to 8.3 ng L−1. Satisfactory linear range was observed from 5.0 to 2000 ng L−1 with correlation coefficient better than 0.9909. Good precisions were also acquired with RSD better than 13.6% for all target analytes. The enrichment factors of the method were ranged from 786 to 1427. The method can be successfully applied to simultaneous separation and determination of three class residues in real water samples and good recoveries were obtained ranging from 76 to 130, 73 to 129, and 78 to 130% for tap water, lake water, and industrial waste water, respectively.

Optimization of simultaneous derivatization and extraction of aliphatic amines in water samples with dispersive liquid–liquid microextraction followed by HPLC

Dispersive liquid-liquid microextraction based on solidification of floating organic droplet (DLLME-SFO) with simultaneous derivatization followed by high-performance liquid chromatography-diode array detection (HPLC-DAD) was applied for preconcentration and determination of primary and secondary aliphatic amines in environmental water samples. A ternary mixture consisting of a disperser, an extractant and a derivatization reagent was used for the simultaneous derivatization and extraction of aliphatic amines in different water samples. The effects of various experimental parameters on derivatization and extraction efficiency were studied simultaneously using experimental design. A Plackett-Burman design was performed for screening of variables in order to determine the significant variables affecting the extraction efficiency. Then, the significant factors were optimized by using a Box-Behnken design (BBD) and the response surface equations were derived. Under optimal conditions, the preconcentration factors were between 210 and 290. The limit of detections (LODs) ranged from 0.005 to 0.02 μg/L and dynamic linear ranges (DLRs) of 0.05-500 and 0.1-500 μg/L were obtained for most of analytes. The performance of the method was evaluated for extraction and determination of primary and secondary aliphatic amines in environmental water samples in micrograms per liter and satisfactory results were obtained (RSDs <12.5%).

Quantification of multi-residue levels in peach juices, pulps and peels using dispersive liquid–liquid microextraction based on floating organic droplet coupled with gas chromatography-electron capture detection

In this paper, polychlorinated biphenyl (PCB), organochlorine pesticide (OCP) and pyrethroid pesticides in peach was investigated by comparing their residual level in peach juice, pulps and peels using dispersive liquid–liquid microextraction based on solidification of floating organic droplet (DLLME-SFO) combined with gas chromatography-electron capture detection (GC-ECD). Extraction conditions such as the type of extractant, volume of extractant and dispersant, salt effect and extraction time were optimized. For juice samples, the linearity of the method was obtained in the range of 10–2000 ng L −1,with determination coefficients > 0.99. The limits of detection (LOD) of the method were ranged between 2.8 and 18.5 ng L −1. For pulp and peel samples, the developed method is linear over the range assayed, 1–20 μg kg −1,with coefficients also >0.99. The relative recoveries of compounds analyzed from juice, pulp and peel samples were in the range of 73–106% with a relative standard deviation between 2.6 and 11.8%. The proposed method was applied to the simultaneous analysis of residues in real peach juice, pulp and peel samples. As a result, there were no target analytes found in peach juices and pulps while 3.3 μg kg −1 cyhalothrin and 3.5 μg kg −1 fenvalerate were found in peels. The experiment results revealed that the pyrethroid residues just deposited on the peels of the fruits, but did not move into pulps and juices.

Dispersive liquid–liquid microextraction based on solidification of floating organic droplet followed by high-performance liquid chromatography with ultraviolet detection and liquid chromatography–tandem mass spectrometry for the determination of triclosan and 2,4-dichlorophenol in water samples

A novel, simple and efficient dispersive liquid–liquid microextraction based on solidification of floating organic droplet (DLLME-SFO) technique coupled with high-performance liquid chromatography with ultraviolet detection (HPLC–UV) and liquid chromatography–tandem mass spectrometry (LC–MS/MS) was developed for the determination of triclosan and its degradation product 2,4-dichlorophenol in real water samples. The extraction solvent used in this work is of low density, low volatility, low toxicity and proper melting point around room temperature. The extractant droplets can be collected easily by solidifying it at a lower temperature. Parameters that affect the extraction efficiency, including type and volume of extraction solvent and dispersive solvent, salt effect, pH and extraction time, were investigated and optimized in a 5 mL sample system by HPLC–UV. Under the optimum conditions (extraction solvent: 12 μL of 1-dodecanol; dispersive solvent: 300 of μL acetonitrile; sample pH: 6.0; extraction time: 1 min), the limits of detection (LODs) of the pretreatment method combined with LC–MS/MS were in the range of 0.002–0.02 μg L −1 which are lower than or comparable with other reported approaches applied to the determination of the same compounds. Wide linearities, good precisions and satisfactory relative recoveries were also obtained. The proposed technique was successfully applied to determine triclosan and 2,4-dichlorophenol in real water samples.

Development of Dispersive Liquid-Liquid Microextraction Based on Solidification of Floating Organic Drop for the Sensitive Determination of Trace Copper in Water and Beverage Samples by Flame Atomic Absorption Spectrometry

A dispersive liquid-liquid microextraction based on solidification of floating organic droplet (DLLME-SFO) has been developed as a new approach for the extraction of trace copper in water and beverage samples followed by the determination with flame atomic absorption spectrometry. In the DLLME-SFO, 8-hydroxy quinoline, 1-dodecanol, and methanol were used as chelating agent, extraction solvent and dispersive solvent, respectively. The experimental parameters related to the DLLME-SFO such as the type and volume of the extraction and dispersive solvent, extraction time, sample volume, the concentration of chelating agent and salt addition were investigated and optimized. Under the optimum conditions, the enrichment factor for copper was 122. The method was linear in the range from 0.5 to 300 ng mL �1 of copper in the samples with a correlation coefficient (r) of 0.9996 and a limit of detection of 0.1 ng mL �1 . The method was applied to the determination of copper in water and beverage samples. The recoveries for the spiked water and beverage samples at the copper concentration levels of 5.0 and 10.0 ng mL �1 were in the range between 92.0% and 108.0%. The relative standard deviations (RSD) varied from 3.0% to 5.6%.

Sensitive determination of in , beverage and cereal samples by a novel liquid-phase microextraction coupled with flame atomic absorption spectrometry.

A new microextraction technique termed dispersive liquid-liquid microextraction based on solidification of floating organic droplet (DLLME-SFO) coupled with flame atomic absorption spectrometry (FAAS) has been developed for the determination of trace cadmium in water, beverage and cereal samples. In the DLLME-SFO, cadmium was first complexed with 8-hydroxyquinoline, and then extracted into a small volume of the extraction solvent (1-dodecanol) with methanol as a dispersive solvent. Then, the extractant was analyzed by FAAS. The main factors affecting the DLLME-SFO, such as the type and volume of the extraction solvent and dispersive solvent, extraction time, sample volume, the amount of chelating agent, and salt addition were optimized. Under the optimum conditions, the established method showed a good linearity within a range of 1-50 ng mL-1, high enhancement factor (133), low limit of detection (0.3 ng mL-1), satisfactory repeatabilities (the relative standard deviation (RSD) = 3.7%, n = 6), and high recoveries (from 91.8 to 104.4%). The method was applied to determine the cadmium in three different samples (water, beverage and cereal samples) and two certified reference materials. The results indicated that the method can be applied for the determination of trace cadmium in real samples with complex matrices.