Volume Of Disperser Solvents Research Articles

In situ generation of hydrophobic magnetic ionic liquids in stir bar dispersive liquid-liquid microextraction coupled with headspace gas chromatography

For the first time, an in situ stir bar dispersive liquid-liquid microextraction approach has been developed and coupled with headspace gas chromatography-mass spectrometry for the determination of a group of organic pollutants. The method exploits a new generation of magnetic ionic liquids (MILs) that contain paramagnetic cations based on Ni2+ or Co2+ metal centers coordinated with either N-butylimidazole or N-octylimidazole ligands and chloride anions. The reactants are added to an aqueous solution containing a high field neodymium rod magnet, followed by the addition of the bis[(trifluoromethyl)sulfonyl]imide anion that promotes a metathesis reaction for the in situ generation of a hydrophobic MIL. Concurrently, a high stirring rate is maintained to exceed the magnetic field of the rod magnet and disperse the generated MIL in the sample solution. When stirring is stopped, the MIL coats the rod magnet due to its paramagnetic nature, facilitating the MIL transfer and subsequent desorption and analysis. Under optimum conditions, the method required a 2.5–18% (w/v) aqueous solution of sodium chloride, 10 mL of sample, 20 or 30 mg of MIL, the addition of a small volume of dispersive solvent, and stirring for 5–7.5 min, depending on the MIL. The method provided limits of detection (LODs) down to 10 μg L−1, adequate reproducibility (with relative standard deviation values lower than 10% for a spiked level of 80 μg L−1), and relative recoveries between 72.5% and 102%. Furthermore, the method was successfully applied in the analysis of tap and mineral water.

Determination of 17 potential endocrine-disrupting chemicals in human saliva by dispersive liquid-liquid microextraction and liquid chromatography-tandem mass spectrometry

Endocrine-disrupting chemicals are a group of emerging contaminants that alters the function of the endocrine system, causing possible adverse health effects. In this study, a dispersive liquid-liquid microextraction method coupled with liquid chromatography-mass spectrometry for the simultaneous determination of 17 potential EDCs, bisphenols (A, S, P, AP, AF, Z), parabens (methyl-, ethyl-, propyl-, butyl-, benzyl-paraben), benzophenones (3, 1, 2, 8, 4-OH BP) and triclocarban, in human saliva samples was developed. Several parameters such as, type and volume of extraction and dispersive solvents, pH sample, ionic strength and, agitation, that affect extraction efficiency were investigated. Under the optimized conditions, the matrix-matched calibration curves of all analytes presented correlation coefficients higher than 0.99 (range level of 1–20 ng mL−1). The intra and inter-day coefficient of variation and relative standard deviation were lower than 20%, at 1 ng mL−1. The limits of detection and quantification ranged from 0.01 to 0.15 ng mL−1 and 0.05–0.40 ng mL−1, respectively. Finally, the proposed method was applied in the simultaneous determination of several endocrine-disrupting chemicals classes in 10 human saliva samples In conclusion, the proposed method is an attractive alternative for application in large-scale human biomonitoring studies.

Optimization of lithium separation conditions from Caspian seawater using fuzzy logic combined with dispersive liquid–liquid extraction

ABSTRACTFor optimization of separation conditions of lithium from the Caspian seawater, a new combination technique of liquid–liquid extraction and fuzzy logic is being used. In this research, disperser and extraction solvents, and ligand of benzo15-crown-5, have been quickly injected. It went to cloudy form solution contain small extraction solvent drops. The impact of different parameters such as the kind and concentration of benzo15-crown-5, the volume of disperser and extraction solvents, pH and extraction time have been optimized on the extraction percentage and analyzed using fuzzy logic. The effect of other metal ion on extraction percentage was also investigated. Under the optimized conditions (volume of tetrachloroethylene: 1.5 mL, volume of acetone: 120 mL, volume of benzo15-crown-5: 0.1 mL, concentration of benzo15-crown-5: 0.001 mol/L, and pH: 1), the extraction has increased to 74% for the synthesis sample and 31% for the real sample from Caspian seawater.

Ionic liquid dispersive liquid-liquid microextraction combined with LC-UV-Vis for the fast and simultaneous determination of cortisone and cortisol in human saliva samples

Ionic liquid dispersive liquid–liquid microextraction (IL-DLLME) was used for the first time for the extraction and preconcentration of cortisone and cortisol from human saliva samples. This approach allows the determination of both compounds by liquid chromatography (LC) with ultra-violet/visible (UV/Vis) detection at physiological levels. The IL 1-butyl-3-methylimidazolium hexafluorophosphate [C4MIM][PF6] and methanol (MeOH) were used as extraction and dispersive solvents, respectively. The parameters that affect extraction (ionic strength, pH, amount of IL, volume of dispersive solvent, vortex and centrifugation time) were optimized. Limits of detection were 0.11 (cortisone) and 0.16 μg L−1 (cortisol) and enrichment factors of 5.0 (cortisol) and 6.3 (cortisone) were achieved. Recoveries from 83.3 ± 1.6 to 115.8 ± 3.0% were obtained for the extraction of the target analytes in spiked human saliva samples. Intraday and interday precision, expressed as relative standard deviation, was below 4.2 and 7.8% for cortisone and cortisol, respectively. The method was successfully applied to the determination of cortisone and cortisol in saliva from healthy volunteers (n = 9) in the morning and in the evening. The method is simple, faster, and more environmentally friendly than the current ones.

Determination of Polycyclic Aromatic Hydrocarbons in Edible Oil Using Fast and Sensitive Microwave-assisted Extraction and Dispersive Liquid–Liquid Microextraction Followed by Gas Chromatography-Mass Spectrometry

Edible oils as important fat-rich samples have the most probability in forming of polycyclic aromatic hydrocarbons. In this research an efficient, sensitive and fast microwave-assisted extraction and dispersive liquid-liquid microextraction (MAE-DLLME) followed by gas chromatography-mass spectrometry (GC-MS) was employed for isolation and determination of PAHs in edible oil. Effective parameters for extraction procedure including type and volume of extraction and disperser solvent, microwave time, NaCl amount and pH were optimized using response surface methodology (RSM) based on central composite design (CCD). In microwave procedure, PAHs extracted from oil sample with acetonitrile/acetone (50:50) and methanolic KOH in two steps. In microextraction stage, mixture of ethanol (disperser solvent), tetrachloroethylene (extraction solvent) and biphenyl (internal standard) was rapidly injected into the sample solution. After performing phase separation, sedimented phase was analyzed by GC-MS. For proposed method, the calibration curve was obtained in the range of 2–500 ng mL−1 with correlation coefficient (R2) 0.9346 to 0.9978. Enrichment factors were between 81 and 124 for PAHs and repeatability as relative standard deviations (RSDs) were 5.2% to 9.1% for all PAH compounds at a concentration of 10 ng mL−1. Limits of detection (LODs) and limits of quantitation (LOQs) were obtained in the range of 0.2–2.7 ng mL−1 and 0.6–9.1 ng mL−1, respectively. Comparison of this method with other analytical method showed that MAE-DLLME coupled with GC-MS is a powerful method for detecting PAHs in complex matrices. The validated method was applied for the determination of PAHs in real edible oil samples and acceptable results were obtained.

Detection of C60 in environmental water using dispersive liquid–liquid micro-extraction followed by high-performance liquid chromatography

ABSTRACTThe wide application of fullerene C60 nanoparticles would inevitably lead to their release into the environment. In order to evaluate the environment risks of C60 and the subsequent effects on ecosystem health, a reliable quantitative methodology of C60 should be established. In this study, a rapid pretreatment method called low-density solvent-based dispersive liquid–liquid micro-extraction (DLLME) combined high-performance liquid chromatography-UV detector (HPLC-UV) was developed to detect C60 in environmental water. In this proposed method, toluene and methanol were chosen as the extraction solvent and the dispersive solvent, respectively. The optimized volume of extraction solvent and dispersive solvent were 100 μL and 10 μL, respectively. And the best shaking time was chosen as 10 min at room temperature for the optimal homogenization procedure for the extraction of C60 in water samples. The enrichment factor of 50 was obtained with 100 μL toluene, and the recoveries of C60 from various environmental samples were in the range of 81.4 ± 5.0–101.4 ± 6.2% at 1.25–5.00 µg/L spiked levels. The detection limits of C60 in tap water, surface water, living sewage and mining waste water were 0.19, 0.29, 0.34 and 0.22 μg/L, respectively. The low detection limit, good linear range and high recoveries of C60 in environmental water indicated that the proposed method could provide an efficient approach for the analysis and tracking of C60 in the environment.

In-syringe solvent-assisted dispersive solid phase extraction followed by flame atomic absorption spectrometry for determination of nickel in water and food samples

This study presents a new in-syringe solvent-assisted dispersive solid phase extraction (ISSADSPE) method for determination of nickel ions in water and food. The method involved dispersion of a few milligrams of sorbent in the sample solution inside the barrel of a syringe through application of a disperser solvent. In less than 1 min, the extraction equilibrium was achieved due to dispersion of the sorbent and high mass transfer rate. Afterwards, syringe membrane was employed to separate the dispersed sorbent from the solution. Then the ethanol was withdrawn by syringe membrane to dissolve the analyte-enriched sorbent. Flame atomic absorption spectroscopy was applied to assess the obtained extract. Effective factors such as the sorbent nature and amount, sample volume, pH, ligand concentration, type and volume of disperser solvent and eluent, ionic strength and extraction time were evaluated and optimized to improve the extraction efficiency. Under optimized conditions (pH = 8.0, ligand concentration = 2.0 × 10−4, sorbent = 10 mg of benzophenone, disperser solvent 500 μL of ethanol), the limit of detection and quantification were found to be 0.7 μg L−1 and 2.0 μg L−1, respectively. The calibration curve kept its linearity from 2 to150 μg L−1, with the square correlation coefficient of 0.997. The relative standard deviation was measured as 2.5% while the enrichment factor was assessed as 50. The proposed method was successfully applied for determination of nickel in environmental water, spinach and celery samples, with recovery range of 97–101%.

Dispersive Liquid-Liquid Microextraction of Famotidine and Nizatidine from Water Samples.

A new extraction method was developed for isolation of the antihistaminic drugs (histamine H2 receptor antagonists) famotidine (FMT) and nizatidine (NZT) from aqueous samples. A low solvent consumption method using dispersive liquid-liquid microextraction (DLLME) was applied for this purpose. The parameters of the isolation, namely, volume of extraction and disperser solvents, pH of sample and shaking time were optimized. The influence of foreign substances on the extraction process was also studied. After separation of FMT and NZT using DLLME, the analytes in organic extracts were determinated by high-performance liquid chromatography combined with UV spectrophotometry and liquid chromatography connected with tandem mass spectrometry (LC-MS-MS). The use of DLLME for selective isolation of analytes enables their preconcentration. Enrichment factors 23 and 61 were obtained for FMT and NZT, respectively. These procedures enable detection of the analytes in real samples at levels 0.24 μg mL-1 (limits of detection (LOD) of FMT: 7.2·10-7 mol L-1 and LOD of NZT: 7.3·10-7 mol L-1). The method was applied for the determination of the studied antihistaminic drugs in river water and wastewater samples. The use of LC-MS-MS in conjunction with DLLME enabled detection of FMT in Netta river at a concentration level of 0.46 ± 0.04 ng mL-1.

Development of dispersive solvent extraction method to determine the chemical composition of apple peel wax

A method to extract apple peel wax was developed using the dispersive solvent extraction technique and applied to four apple cultivars (Royal Gala, Pink Lady®, Red Delicious, and Granny Smith). Different variables of the method were optimized, namely type and volume of extraction and dispersive solvents, ionic strength, and use of ultrasound. Extracts were evaluated as gravimetric yield of wax and composition as determined by gas chromatography. Optimized conditions provided yields higher than 95%. In a repeatability assay, the relative standard deviation for the extracted wax content was <3%. Thirty-one wax compounds were identified, among them fatty acids, hydrocarbons, sterols, and terpenes. Fatty acids were the major constituents in the analyzed extracts. N-alkane, nonacosane, and triterpene ursolic acid were also significant constituents. The method allows the determination of the total peel wax content and the different constituents of this fraction from distinct apple cultivars.

Dispersive liquid-liquid microextraction followed by gas chromatography–mass spectrometry for the determination of pesticide residues in nutraceutical drops

An economical and rapid method has been developed using dispersive liquid-liquid microextraction (DLLME) coupled with gas chromatography–mass spectrometry to extract and determine forty pesticides in nutraceutical drops containing alcohol. Parameters affecting the DLLME performance, such as solvent selection and volume of extractive and dispersive solvent, salt effect, pH, mixing type and extraction time, were studied. Tetrachloroethane was the selected extraction solvent. Ethanol contained in the sample was enriched by methanol to serve as dispersive solvent. The method was fully validated under the optimized extraction parameters. The recoveries of pesticides were between 70 and 120% with relative standard deviations less than 20%. The limits of detection ranged from 0.001 to 0.910 μg/L and the limits of quantification ranged from 0.004 to 3.003 μg/L. The optimized method was employed for determination of pesticide residues in real samples of nutraceutical drops and herbal alcoholic beverages.

Dispersive Liquid–Liquid Microextraction Based on Solidification of Floating Organic Drop for Isolation and Determination of Opium Alkaloids

Abstract—In this study, a simple, rapid and sensitive method for determination of opium alkaloids in urine and hair samples was developed. The method is based on the combination of dispersive liquid–liquid microextraction–solidified floating organic drop and high-performance liquid chromatography–ultraviolet detection. The extraction of opium alkaloids was influenced by various parameters such as nature and volume of extraction solvent and dispersive solvent, sample pH and volume. At optimum conditions and preconcentration from 10 mL, the detection limits of 17 and 10 µg/L, linear dynamic ranges of 50–1170 and 20–2340 µg/L and relative standard deviations of 1.5 and 4.6% (n = 6) at 600 µg/L were obtained for morphine and codeine, respectively. The method was successfully applied to the determination of morphine and codeine in urine and hair samples.

Vortex-assisted liquid-liquid microextraction based on hydrophobic deep eutectic solvent for determination of malondialdehyde and formaldehyde by HPLC-UV approach

A simple, and cost-effective vortex-assisted liquid-liquid microextraction (VALLME) based on hydrophobic deep eutectic solvent (DES) has been developed to extract malondialdehyde (MDA) and formaldehyde (FA) after derivatization with 2,4-dinitrophenylhydrazine (DNPH). Following the extraction process, a high performance liquid chromatography equipped with UV–Vis detector (HPLC-UV) was used for separation and quantification of the target analytes. The key variables affecting the derivatization process (concentration of DNPH, derivatization time, and derivatization temperature) were optimized by a central composite design (CCD). The effective parameters of VALLME including pH of the extraction medium, ionic strength, extracting agent (DES) volume, dispersive solvent volume, centrifugation rate, centrifugation time, and time of vortex were studied by a fractional factorial design to identify the significant factors effective in the extraction process. In the next step, a CCD was used to obtain the optimum conditions of the effective parameters. Under optimal conditions, good linearities (R2 > 0.99) in the concentration ranges of 5–3000 and 20–2000 ng mL−1 were obtained for MDA and FA, respectively. The detection limits of MDA and FA were found as 2.0 and 10.0 ng mL−1, respectively. The method was successfully applied to the quantification of both analytes in three different real samples (human urine, apple juice and rain water) and satisfactory results in terms of recoveries (91–112%) were achieved.

Simultaneous determination of seven preservatives in food by dispersive liquid-liquid microextraction coupled with gas chromatography-mass spectrometry

A simple, rapid, inexpensive and environment-friendly method, based on dispersive liquid-liquid microextraction (DLLME) coupled with gas chromatography-mass spectrometry (GC–MS), was developed for the determination of food preservatives including benzoic acid (BA), sorbic acid (SA), dehydroacetic acid and four parabens. Optimum DLLME conditions were determined as follows: extraction solvent (chloroform) volume, 50 μL; disperser solvent (acetone) volume, 0.5 mL; NaCl amount, 0.50 g/4 mL sample solution at pH 4.0. Hydroquinone was selected as the internal standard. The calibration curves were linear in the range 0.05–10 mg L−1 for BA, SA and methylparaben, and 0.02–10 mg L−1, for the remainder. Limits of detection were in the range 0.15–0.50 mg kg−1 with enrichment factors ranging from 25 to 114 for all target analytes. Recoveries were in the range 88.7–110.5% with a relative standard deviation of less than 5%.

Synthesis of graphene oxide/polyaniline nanocomposite for measuring cadmium(II) by solid phase extraction combined with dispersive liquid-liquid microextraction

An analytical route containing solid-phase extraction combined with dispersive liquid–liquid microextration (SPE–DLLME), was established to determine Cd ions in water samples. In this regard, Graphene oxide/polyaniline nanocomposite was synthesized through chemical method and then the graphene oxide/polyaniline nanocomposite was characterized by using XRD, FESEM, FTIR and TGA techniques. The prepared nanocomposite was investigated as a adsorbent in the presence of chelating dithizone ligand in solid phase extraction with dispersive liquid-liquid microextraction and used to measure cadmium (II) ions in aqueous media. In this method, firstly; single-variable parameters such as the amount of adsorbent, extraction time, type of desorption solvent, desorption time were investigated. Then, with using the design of expert, the parameters affecting the extraction efficiency such as the effect of salt addition (ionic strength), pH, volume of extraction solvent and the volume of dispersive solvent have been optimized. The analytical figure of merit such as limit of detection (0.1 μg L−1), limit of quantification (0.4 μg L−1), linear dynamic ange (0.4–1000 μg L−1), repeatability (%1.3), enrichment factor (210) and relative recovery percentage (99%), were obtained for cadmium (II) spike aqueous samples. Finally, the method was successfully used and evaluated for the extraction and quantification of Cd ions from real samples and relative recoveries varied from 91%–107%.

Simultaneous determination of valproic acid and its main metabolite in human plasma using a small scale dispersive liquid–liquid microextraction followed by gas chromatography–flame ionization detection

A simple, sensitive, and rapid analytical method has been developed and validated for the extraction and quantification of valproic acid and its main metabolite (3-heptanone) in human plasma. Initially, the proteins of plasma were precipitated with trifluoroacetic acid. Then a very small volume of a water-immiscible extractant and acetonitrile was mixed and rapidly injected into the pre-treated plasma sample. For further turbidity (dispersion of the extractant into sample solution), the cloudy solution was vortexed. After centrifugation, the settled phase was injected into gas chromatography-flame ionization detection. The effective parameters, such as type and volume of extraction and disperser solvents, vortex time, and pH were studied and optimized. The limits of detection of valproic acid and 3-heptanone were obtained, 0.065 and 0.015 mg L−1, respectively. An acceptable precision was obtained for a concentration of 2 mg L−1 of each analyte (relative standard deviation ≤ 8%). The average absolute recoveries (n = 3) of valproic acid and 3-heptanone were 52 ± 2 and 42 ± 1%, respectively. The validated method has been successfully used in analysis of the analytes in human plasma samples.

Thin-Layer Chromatography: an Efficient Technique for the Optimization of Dispersive Liquid-Liquid Microextraction.

Thin-layer chromatography (TLC) is an often omitted analytical technique due to its lower sensitivity and separation capacity. Even in the era of high-performance liquid chromatography (HPLC), thin-layer chromatography still offers many advantages, such as simplicity, rapidity, and cost-effectiveness, which predict TLC to be the first-choice method for the laborious optimization process requiring analysis of numerous samples. In this work, a thin-layer chromatography method with chemical and densitometric detection was used to optimize a dispersive liquid-liquid microextraction (DLLME) process for the extraction and preconcentration of estradiol in human urine. The chromatographic system consisted of silica gel plates as the stationary phase and toluene-ethanol (9:1; v/v) mixture as the developing solvent. The plates were dyed with 10% phosphomolybdic acid reagent and sequentially evaluated densitometrically at λ = 430 nm. In the context of DLLME optimization, parameters including the type and volume of extraction and dispersive solvents, centrifugation, salt addition and extraction time, were studied. The proposed DLLME-TLC method was successfully applied to the determination of estradiol in real human urine samples.

Optimization of a methodology for determination of iron concentration in aqueous samples using a newly synthesized chelating agent in dispersive liquid-liquid microextraction

The aim of this study was to establish a new dispersive liquid-liquid microextraction (DLLME) technique for the determination of iron concentration in aqueous solutions and fruit juices based on the reaction between iron and 3-hydroxy-1-(3-hydroxyphenyl)-2-methylpyridin-4(1H)-one (3-OH-PMPO) as a chelating agent. A central composite design (CCD) was applied to optimize the effects of independent parameters (pH, volume of disperser solvent and extractant solvent and chelating agent concentration) on extraction efficiency. Under the optimized conditions, the analytical curve is linear in a concentration range of 10–750 μgL−1 with a detection limit of 5 μgL−1. The relative standard deviation (RSD) for ten repeated determinations of iron concentrations at 40 and 200 μgL−1 was calculated to be 4.2% and 1.2%, respectively. Relative recovery of iron in several water samples was investigated and the average was obtained in the range of 91–108%.

Analysis of malondialdehyde in human plasma samples through derivatization with 2,4-dinitrophenylhydrazine by ultrasound-assisted dispersive liquid–liquid microextraction-GC-FID approach

A sensitive and reliable ultrasound-assisted dispersive liquid–liquid microextraction (UA-DLLME) procedure was developed and validated for extraction and analysis of malondialdehyde (MDA) as an important lipids-peroxidation biomarker in human plasma. In this methodology, to achieve an applicable extraction procedure, the whole optimization processes were performed in human plasma. To convert MDA into readily extractable species, it was derivatized to hydrazone structure-base by 2,4-dinitrophenylhydrazine (DNPH) at 40 °C within 60 min. Influences of experimental variables on the extraction process including type and volume of extraction and disperser solvents, amount of derivatization agent, temperature, pH, ionic strength, sonication and centrifugation times were evaluated. Under the optimal experimental conditions, the enhancement factor and extraction recovery were 79.8 and 95.8%, respectively. The analytical signal linearly (R2 = 0.9988) responded over a concentration range of 5.00–4000 ng mL−1 with a limit of detection of 0.75 ng mL−1 (S/N = 3) in the plasma sample. To validate the developed procedure, the recommend guidelines of Food and Drug Administration for bioanalytical analysis have been employed.

Trace determination of cobalt in biological fluids based on preconcentration with a new competitive ligand using dispersive liquid-liquid microextraction combined with slotted quartz tube–flame atomic absorption spectrophotometry

A new competitive ligand has been synthesized for the preconcentration to obtain lower detection limits by using dispersive liquid-liquid microextraction combined with slotted quartz tube-flame atomic absorption spectrophotometry (DLLME-SQT-FAAS). The proposed method is simple, eco-friendly and has high sensitivity. The preconcentration procedure was optimized on the basis of various parameters affecting the complex formation and extraction efficiency such as pH and volume of buffer solution, volume of ligand solution, mixing period, volume and type of extraction solvent, volume and type of dispersive solvent, and salt effect. Instrumental parameters were also optimized to get higher sensitivity. Under the optimum conditions, the calibration graph was linear in the range of 10–250 ng mL−1and the resulted limits of detection and quantification (LOD and LOQ) for combined method were 4.7 and 15.7 ng mL−1, respectively. The detection power was improved 48-fold using DLLME-SQT-FAAS method compared to conventional FAAS. The precision of the method was found to be high with a relative standard deviation of 2.5%. The accuracy of method was evaluated by recovery experiments using matrix matching study on spiked urine and blood samples. The recoveries for urine and blood samples ranged from 99.8 to 108.9% and 102.5 to 110.0%, respectively.

Development of Dispersive Liquid-Liquid Microextraction method combined with UV spectrophotometry for the Determination of Malathion Pesticide

A simple and novel method was developed by combination of dispersive liquid-liquid microex-traction with UV spectrophotometry for the preconcentartion and determination of trace amount of malathion. The presented method is based on using a small volume of ethylenechloride as the extraction solvent was dissolved in ethanol as the dispersive solvent, then the binary solution was rapidly injected by a syringe into the water sample containing malathion. The important parame-ters, such the type and volume of extraction solvent and disperser solvent, the effect of extraction time and rate, the effect of salt addition and reaction conditions were studied. At the optimum conditions, the calibration graph was linear in the range of 2-100 ng mL-1 of malathion with a limit of detection of 0.8 ng L-1. In addition, the enrichment factor was 30. The developed method was successfully applied for the determination of malathion pesticide in water samples