Dispersive Liquid-liquid Extraction Research Articles

Optimization and comparison of membrane-protected micro-solid-phase extraction coupled with dispersive liquid-liquid microextraction for organochlorine pesticides using three different sorbents

A micro-solid-phase extraction technique has been developed, for determination of organochlorine pesticides in water media, using gas chromatography-electron capture detector. Response surface methodology was applied to optimize the performance of the extraction technique. Also, the effect of significant experimental parameters (i.e. extraction time, ionic strength, type and volume of the desorption solvent and desorption time) has been studied. Three frequently used solid sorbents; multi-walled carbon nanotube, silica-based C18, and polymeric solid sorbent (LiChrolut® EN), were implemented and independently optimized and the results were compared to find the best extraction setup. A dispersive liquid-liquid extraction procedure was also used to enhance the sensitivity of the method, showing enrichment factors of 14 to 40. The limits of detection of the optimized technique were less than 0.26 μg L−1 (for methoxychlor with C18) and RSD values were between 3.3 and 14.5% at 1 μg L−1. The calibration functions were linear up to 500 μg L−1 with R2 values of more than 0.995, for all sorbents. The figures of merit of the entire procedure showed that each of the studied sorbents could produce satisfactory results in ultra-trace determination organochlorine pesticides in water.

Quality Control of the Migration of Bisphenol a from Plastic Packaging into Iranian Brands of Food Grade Oils

Background: Bis-phenol A (BPA) can migrate into food stuff from packaging materials and accounts for food contamination. This research was designed to measure BPA contamination in the Iranian brands of food grade oils and to find out the possible effect of production date on the amount of BPA migration. Methods: Ten well-known and top selling oils packed in various containers, were selected and sampled according to their batch number and production date stated on the label. Subsequently, BPA was extracted by reverse phase dispersive liquid-liquid extraction (RP-DLLME) method and quantified by HPLC. Results: The measured quantity of BPA in the food grade oil was ranged between 0.5 to 4.37 µg/g of oil samples regardless of the date of production, the Batch Number, and the producing company. Statistical analysis revealed that the difference of BPA content in oil samples did not depend on their production date. Conclusion: According to the amount of allowable migration introduced by European committee, the amount of BPA migration and consequently contamination of almost all tested samples exceeds SML. Considering the toxic effects reported especially in fetus and young children, prompt regulatory interference is needed in this area.

Application of response surface methodology to vortex-assisted dispersive liquid-liquid extraction for the determination of nicotine and cotinine in urine by gas chromatography-tandem mass spectrometry.

A method of vortex-assisted dispersive liquid-liquid extraction coupled with gas chromatography and tandem mass spectrometry for the determination of nicotine and cotinine in urine was developed. Response surface methodology was applied to obtain the optimum extraction conditions. In this method, Plackett-Burman design was utilized to evaluate the impact of five selected factors on pretreatment procedure. Then, three main factors were optimized using a Box-Behnken design. The optimized method showed good linearities at 1-2000μg/L with correlation coefficients of 0.9998 for nicotine and 0.9986 for cotinine. Recovery was 91.4-106 and 91.7-108% for nicotine and cotinine, respectively. The intraday relative standard derivations of determination were 1.47-4.06% for nicotine and 0.41-3.16% for cotinine, and interday relative standard derivations were 3.03-6.70% for nicotine and 1.64-6.38% for cotinine. The method detection limits for nicotine and cotinine were 0.33 and 0.34μg/L, respectively. A total of 87 urine samples from smokers and nonsmokers were tested with the proposed method. Urinary nicotine and cotinine were 23.0-6.67 × 103 and 18.4-4.17 × 103 μg/(g·cr) for smokers and 1.31-286 and 1.39-131μg/(g·cr) for nonsmokers, respectively. The method is sensitive, suitable and reliable for the determination of nicotine and cotinine in urine and meets the requirements for evaluating short-term tobacco exposure.

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.

Simple and Rapid Dual-Dispersive Liquid-Liquid Microextraction as an Innovative Extraction Method for Uranium in Real Water Samples Prior to the Determination of Uranium by a Spectrophotometric Technique.

An innovative, rapid, and simple dual-dispersive liquid-liquid microextraction (DDLL-ME) approach was used to extract uranium from real samples for the first time. The main objective of this study was to disperse extraction solvent by using an air-agitated syringe system to overcome matrix effects and avoid dispersion of hazardous dispersive organic solvents by using heat. The DDLL-ME method consisted of two dispersive liquid-liquid extraction steps with chloroform as the extracting solvent. Uranium formed complexes with 4-(2-thiazolylazo) resorcinol in the aqueous phase and was extracted in extracting solvent (chloroform) after the first dispersive liquid-liquid process. Uranium was then back-extracted in the acidic aqueous phase in a second dispersive liquid-liquid process. Finally, uranium was determined by a spectrophotometric detection technique. The variables that played a key role in the proposed method were studied and optimized. The LOD and sensitivity enhancement factor for uranium were found to be 0.60 µg/L and 45, respectively, under optimized conditions. Calibration graphs were found to be linear in the range of 5.0-600 µg/L. The RSD was 2.5%. Reliability of the proposed method was verified by analyzing certified reference material TM-28.3.

Determination of Trace Amount of Lead in Industrial and Municipal Effluent Water Samples Based on Dispersive Liquid-Liquid Extraction

In this study, a simple, sensitive and accurate method was developed for the determination of lead ion by combining ionic liquid dispersive liquid-liquid extraction (IL-DLLE) with flame atomic absorption spectrometry. Tetraethylthiuram disulfide (TETD), acetone and 1-octyl-3-methylimidazolium hexafluorophosphate [(C8MIM) (PF6)] were used as the chelating agent, dispersive and extraction solvent, respectively. Under the optimal onditions, the calibration graph was linear in the range of 5-190 μg L-1 of lead and the detection limit was 0.8 μg L-1 with a sample volume of 200 mL. The proposed method was validated by the analysis of one certified reference material and applied successfully to the determination of lead in real water samples.

Matrix Solid-Phase Dispersion Based on Carbon Nanotube Coupled with Dispersive Liquid-Liquid Microextraction for Determination of Organochlorine Pesticides in Soil.

The presented article describes the methodology and results of investigating the capability of multi-walled carbon nanotube as sorbent in an efficient extraction method for determination of organochlorine pesticides, α-BHC, β-BHC, γ-BHC, heptachlor, endrin, aldrin, 4,4'-DDD, 4,4'-DDE and 4,4'-DDT, in soil media. Matrix solid-phase dispersion was optimized for extraction from small amounts of soil samples and the resulting extracts were pre-concentrated using dispersive liquid-liquid microextraction. The most important experimental parameters of both extraction procedures were studied and the optimum conditions for simultaneous analysis of the target analytes were determined. In the final analysis procedure, a 0.20 g portion of dried soil sample was extracted by dichloromethane after being mixed with 0.020 g of carbon nanotube and 0.400 g of silica gel. Then, dispersive liquid-liquid extraction was used to pre-concentrate the extract before injecting the sample into the gas chromatographic system. The pre-concentration step showed to have up to 32 times of enrichment capability and the total procedure had reasonable sensitivity and reproducibility, withlimit of detections <1.6 ng g-1 and relative standard deviation values below 8.1%, respectively. It was also demonstrated that the organic content of the soil can alter the extraction efficiency (70-105%), depending on both the amount of the organic matter and the individual analyte. Therefore, the importance of matrix spike samples, throughout the method validation procedure, was confirmed.

Separation of uranium (VI) using dispersive liquid-liquid extraction from leach liquor

A dispersive liquid–liquid extraction technique was applied for evaluation of optimal conditions of uranium (VI) separation from aqueous solution (It is actual leach liquor, containing uranium (VI), thorium (IV), iron (III), Cl−, SO42−, etc). In this procedure, an appropriate mixture of the disperser and extraction solvents was added rapidly to the aqueous sample containing uranium ion; as a result, a cloudy solution was formed which consisted of fine droplets of extraction solvent dispersed entirely throughout the aqueous phase. The cloudy solution was centrifuged and the fine droplets of the extraction solvent were settled at the bottom of the conical test tube. The analytes were extracted from the source solution into the receiving phase and were concentrated to a small volume of the settled phase and finally, the inductively coupled plasma optical emission spectrometry was used to determine the analyte concentration in the settled phase. The conditions for the batch extraction performance were optimized; Furthermore, the continuous packed tower with 5 cm of diameter and 30 cm of height was applied to examine the batch results of continuous condition on an industrial-scale. The results showed that for 41.2% and 90% recovery factors of uranium (VI) from the leach liquor solution, one equilibrium stage and five equilibrium stages are needed, respectively.

Application of low density miniaturized dispersive liquid-liquid extraction method for determination of formaldehyde in aqueous samples (water, fruit juice and streptococcus vaccine) by HPLC-UV

A simple method based on miniaturized dispersive liquid–liquid extraction is reported for extraction and preconcentration of formaldehyde in water samples. Eight milliliters of an aqueous sample containing 2,4-dinitrophenylhydrazine were added to a 10.0 mL volumetic flask containing 1.0 mL of methanol–butyl acetate (2: 1) mixture. After phase separation the analyte was determined by HPLC-UV. No clean-up or evaporation were required after extraction. Several factors influencing the extraction efficiency, such as the type and volume of organic solvent, type and volume of co-solvent, pH of the sample solution, ionic strength, and extraction time were evaluated and optimized. Under optimal experimental conditions, good linearity was obtained in the range of 1.5 × 10–4–10 µg/mL (r = 0.996), and the limit of detection was 5 × 10–5 µg/mL. The method produced 20-fold enrichment of the formaldehyde. The average recovery of spiked formaldehyde in real samples was in the range of 90–110% with RSD in the range of 3–8%.

Separation of Vanadium Using Dispersive Liquid-Liquid Extraction

In this study, the conditions of vanadium separation from wastewater by dispersive liquid-liquid extraction in batch and continuous states have been investigated. The best extractant solvents and dispersive or diluents have been selected and then the effect of pH and, the best time of separation have been optimized. Also, effect of foreign ions was tested and at last vanadium of wastewater has been extracted by Di-(2- ethylhexyl) phosphoric acid and amines (Tri-C8-C10–alkyl amine). The results show that amines better than Di-(2- ethylhexyl) phosphoric acid in the present foreign ions can extract vanadium. Under the best optimized conditions, the extraction amounts increased from 34.67% to 92.7%. Methanol with Di-(2-ethylhexyl) phosphoric acid is the best dispersive solvent for extraction of vanadium and, acetonitrile is as a dispersive solvent for amines. Diagram of the McCabe-Thiel shows nine theoretical stages at flow ratio of 0.5:5 (organic to aqueous) with a residence time of about 100s need for yield 90%.

Ultrasound-Assisted Low-Density Solvent Dispersive Liquid-Liquid Extraction for the Determination of Amphetamines in Biological Samples Using Gas Chromatography-Mass Spectrometry

In order to control drug crime effectively, it is necessary to develop selective analytical methods suitable for unambiguous identification and determination of drugs in illicit samples and biological matrices. A novel microextraction technique based on ultrasound-assisted low-density solvent dispersive liquid-liquid microextraction, (UA-LDS-DLLME) has been applied to the determination of four amphetamines (methamphetamine, amphetamine, 3,4-methylenedioxymethamphetamine, and 3,4-methylenedioxyamphetamine) in urine samples by gas chromatography-mass spectrometry. The parameters affecting extraction efficiency have been investigated and optimized. UA-LDS-DLLME used ultrasound energy to assist in the emulsification process without any disperser solvent. Under the optimized conditions, linearity was observed for all analytes in the 0.15–10 μg/mL range with correlation coefficients (R) ranging from 0.9886 to 0.9894. The recoveries of 75.6–91.4% with relative standard deviations of 2.5–4.0% were obtained. The limits of detection (S/N = 3) were estimated to be in the 5–10 ng/mL range. The UA-LDS-DLLME technique had the advantages of shorter extraction time, suitability for simultaneous pretreatments of batches of samples, and the higher extraction efficiency. It was successfully applied to the analysis of amphetamines in real human urine samples.

Comparative study for determination of some polycyclic aromatic hydrocarbons ‘PAHs’ by a new spectrophotometric method and multivariate calibration coupled with dispersive liquid–liquid extraction

A modified dispersive liquid–liquid extraction (DLLE) procedure coupled with spectrophotometric techniques was adopted for simultaneous determination of naphthalene, anthracene, benzo(a)pyrene, alpha-naphthol and beta-naphthol in water samples. Two different methods were used, partial least-squares (PLS) method and a new derivative ratio method, namely extended derivative ratio (EDR).A PLS-2 model was established for simultaneous determination of the studied pollutants in methanol, by using twenty mixtures as calibration set and five mixtures as validation set. Also, in methanol a novel (EDR) method was developed for determination of the studied pollutants, where each component in the mixture of the five PAHs was determined by using a mixture of the other four components as divisor.Chemometric and EDR methods could be also adopted for determination of the studied PAH in water samples after transferring them from aqueous medium to the organic one by utilizing dispersive liquid–liquid extraction technique, where different parameters were investigated using a full factorial design.Both methods were compared and the proposed method was validated according to ICH guidelines and successfully applied to determine these PAHs simultaneously in spiked water samples, where satisfactory results were obtained. All the results obtained agreed with those of published methods, where no significant difference was observed.

Novel Method for Determination of Anthracene by Coupling Dispersive Liquid-Liquid Extraction to First-Derivative Synchronous Spectrofluorimetry

A novel method could be adopted successfully for determination of anthracene in environmental samples, utilizing dispersive liquid-liquid extraction followed by first-derivative synchronous fluorimetry at a constant wavelength difference Δλ = 165 nm, where a linear calibration curve was obtained in a concentration range of 0.5-100 ng mL(-1) at 244 nm. The detection limit was 0.1 ng mL(-1). The method can be easily adopted for determination of anthracene in aqueous media including tap water and river water. The recoveries obtained were 85.40-108.02%. The proposed method was validated according to International Conference of Harmonization (ICH) guide lines and successfully applied to determine anthracene in pure form and in water samples including real life water samples from different sources. All the results obtained were compared with those of published method, where no a significant difference was observed.

Nonchromatographic Speciation of Selenium in Edible Oils Using Dispersive Liquid–Liquid Microextraction and Electrothermal Atomic Absorption Spectrometry

A methodology for the nonchromatographic separation of the main selenium species present in edible oils is presented. Dispersive liquid-liquid microextraction is used to extract inorganic selenium (iSe), seleno-L-cystine (SeCys₂), seleno-L-methionine (SeMet), and selenocystamine (SeCM) into a slightly acidic aqueous medium. The selenium total (tSe) content is measured in the extracts by electrothermal atomic absorption spectrometry. By repeating the microextraction stage using an ionic liquid instead of water, the sum of SeCys₂, SeMet, and SeCM is obtained and iSe is calculated by difference. The detection limit is 0.03 ng of Se per gram of oil. The fractionation of the edible oils by solid phase extraction followed by dispersive liquid-liquid extraction and atomic absorption measurement also permits speciation of iSe to be carried out. Data for tSe and iSe levels of 15 samples of different origin are given.

Dispersive Liquid−Liquid Microextraction Coupled with Dispersive μ-Solid-Phase Extraction for the Fast Determination of Polycyclic Aromatic Hydrocarbons in Environmental Water Samples

A new two-step microextraction technique, combining dispersive liquid-liquid microextraction (DLLME) and dispersive microsolid-phase extraction (D-micro-SPE), was developed for the fast gas chromatographic-mass spectrometric determination of polycyclic aromatic hydrocarbons (PAHs) in environmental samples. A feature of the new procedure lies in that any organic solvent immiscible with water can be used as extractant in DLLME. A special apparatus, such as conical-bottom test tubes, and tedious procedures of centrifugation, refrigeration of the solvent, and then thawing it, associated with classical DLLME or similar techniques are not necessary in the new procedure, which potentially lends itself to possible automation. In the present D-micro-SPE approach, hydrophobic magnetic nanoparticles were used to retrieve the extractant of 1-octanol in the DLLME step. It is noteworthy that the target of D-micro-SPE was the 1-octanol rather than the PAHs. Because of the rapid mass transfer associated with the DLLME and the D-micro-SPE steps, fast extraction could be achieved. Parameters affecting the extraction efficiency were investigated in detail. The optimal conditions were as follows: vortex at 3200 rpm in the DLLME step for 2 min and in D-micro-SPE for 1 min and then desorption by sonication for 4 min with acetonitrile as the solvent. The results demonstrated that enrichment factors ranging from 110- to 186-fold were obtained for the analytes. The limits of detection and the limits of quantification were in the range of 11.7-61.4 pg/mL and 0.04-0.21 ng/mL, respectively. The linearities were 0.5-50, 1-50, or 2-50 ng/mL for different PAHs. Finally, the two-step extraction method was successfully used for the fast determination of PAHs in river water samples. This two-step method, combining two different and efficient miniaturized techniques, provides a fast means of sample pretreatment for environmental water samples.

5624616 Method for co-refining dry urban wood chips and blends of dry urban wood chips and thermoplastic resins for the production of high quality fiberboard products: Brooks S Hunter W Rochester, MI, United States

A modified dispersive liquid–liquid extraction (DLLE) procedure coupled with spectrophotometric techniques was adopted for simultaneous determination of naphthalene, anthracene, benzo(a)pyrene, alpha-naphthol and beta-naphthol in water samples. Two different methods were used, partial least-squares (PLS) method and a new derivative ratio method, namely extended derivative ratio (EDR).A PLS-2 model was established for simultaneous determination of the studied pollutants in methanol, by using twenty mixtures as calibration set and five mixtures as validation set. Also, in methanol a novel (EDR) method was developed for determination of the studied pollutants, where each component in the mixture of the five PAHs was determined by using a mixture of the other four components as divisor.Chemometric and EDR methods could be also adopted for determination of the studied PAH in water samples after transferring them from aqueous medium to the organic one by utilizing dispersive liquid–liquid extraction technique, where different parameters were investigated using a full factorial design.Both methods were compared and the proposed method was validated according to ICH guidelines and successfully applied to determine these PAHs simultaneously in spiked water samples, where satisfactory results were obtained. All the results obtained agreed with those of published methods, where no significant difference was observed.