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

Microextraction procedures for preconcentration of Fe (III) in water and food samples prior to colorimetric detection: a comparative study

Two extraction procedures, namely dispersive liquid-liquid microextraction (DLLME) and dispersive liquid-liquid microextraction based on solidification of floating organic drop (DLLME-SFOD), have been compared for the spectrophotometric determination of Fe (III). In both procedures, Fe (III) was extracted after complexation with gallic acid in the presence of cetyltrimethylammonium bromide (CTAB). Tetrachloroethylene and 1-undecanol were used as extraction solvents in DLLME and DLLME-SFOD, respectively, while acetone was used as dispersing solvents. The effects of various experimental parameters (solution pH, the concentration of ligand and CTAB, as well as nature and amount of extraction and disperser solvents) on the extraction efficiency were investigated. Under optimum conditions, the calibration graphs were linear in the range of 50.0–650.0 and 8.0–800.0 μg L−1 and the detection limits were 15.0 and 5.0 μg L−1 for DLLME and DLLME-SFOD, respectively. The presence of NaCl, up to 1.0% (w/v) did not impact the extraction procedures. The analyte was good tolerated in the presence of most concomitant ions. The procedures were applied for the determination of Fe (III) in standard reference materials and real samples with good recoveries (95.5–99.0%) for DLLME-SFOD while poor recoveries (68.0–82.5%) were obtained when DLLME was applied. The analytical figures of the procedures were comparable with those listed in the literature and it could be concluded that DLLME-SFOD may be considered one of the best tools used for preconcentration of Fe (III), owing to its simplicity, time-saving and the possibility of using in conventional analytical laboratories.Graphical abstract

Application of dispersive liquid–liquid microextraction based on solidification of floating organic drop for the determination of extractables from pharmaceutical packaging materials

A new method was established for the determination of the extractables from pharmaceutical packaging materials using dispersive liquid–liquid microextraction based on solidification of floating organic drop (DLLME-SFO) coupled with ultra-high-performance liquid chromatography quadrupole time-of-flight mass spectrometry (UHPLC-QTOF MS). Packaging samples were filled with three kinds of buffer solutions: acid buffer (pH = 3), alkaline buffer (pH = 9) and 0.9% NaCl solution to extract as many extractables as possible, and then the extractables in buffer solutions were enriched by DLLME-SFO technique. Parameters affecting the efficiency of the extraction procedure were evaluated and optimized, including the type and volume of dispersant, extractant volume, pH and vortex-mixing time. After optimization, the values obtained for limits of detection and quantification for three kinds of common antioxidants were 0.3 and 1.0 μg/L respectively, and good linearity (R2 > 0.99) was observed in their respective concentration ranges. The recoveries ranged from 80.61% to 117.87% at three spiked levels with the relative standard deviations (RSDs) between 0.92% and 9.29% (n = 6) in all three buffer solutions. The developed method was successfully applied to the analysis of extractables from pharmaceutical packaging materials. The results indicated that the proposed procedure is a novel, sensitive, fast and repeatable method and has a great significance for evaluation of safety of pharmaceutical packaging materials.

Solid-phase extraction combined with dispersive liquid-liquid microextraction/HPLC-UV as a sensitive and efficient method for extraction, pre-concentration and simultaneous determination of antiretroviral drugs nevirapine, efavirenz and nelfinavir in pharmaceutical formulations and biological samples

Therapeutic drug monitoring (TDM) of antiretroviral drugs requires accurate and precise analysis of their trace amounts in plasma samples. Solid-phase extraction (SPE) coupled with dispersive liquid-liquid microextraction based on solidification of floating organic drop (DLLME-SFO) was introduced as a simple and sensitive method for extraction, pre-concentration and simultaneous determination of efavirenz (EFV), nelfinavir (NFV) and nevirapine (NVP) in human plasma and pharmaceutical formulations by using high performance liquid chromatography (HPLC) with UV detection. A response surface methodology (RSM) based on central composite design (CCD) was used for optimizing the main variables in the extraction procedure. Under the optimum experimental conditions, the calibration curves were linear in the range of 0.1–400 ng mL−1 with correlation coefficients from 0.9982 to 0.9997 and limits of detection (at S/N = 3) of 0.03 to 0.07 ng mL−1. Moreover the intra-day and inter-day precision (RSD%) were in the range of 2.2–4.2% and 3.1–5.2%, respectively. The enrichment factors and relative recoveries of the anti-HIV drugs were 459–1507 and 93.7–105.4%. The method was successfully applied to the simultaneous determination of the trace amounts of the antiretroviral drugs in blood plasma and pharmaceutical formulations.

Comparison of Two Liquid-Liquid Microextractions for the Detection of Crocin in the Saffron and Biological Samples Using UV- Vis Spectrophotometry

In this work, two approaches based on Dispersive Liquid-Liquid MicroExtraction (DLLME) and Dispersive Liquid-Liquid MicroExtraction based on Solidification of Floating Organic Drop (DLLME-SFO) were compared for the extraction and preconcentration of crocin from saffron and biological samples. Different DLLME and DLLME-SFO parameters influencing the extraction efficiency were studied and optimized. The results showed that both extraction methods exhibited good linearity, precision, enrichment factor, and detection limit. Under optimal conditions, the limits of detection were 0.008 and 0.005 ng/mL for DLLME and DLLME-SFO, respectively. The preconcentration factors were 88 and 95 for DLLME and DLLME-SFO, respectively. The applicability of the proposed methods was examined by analyzing crocin in saffron, urine and milk samples and good results were obtained. The percentage recovery values for spiked samples were between 96.4 and 99.1.

Dispersive liquid-liquid microextraction based on solidification of floating organic drop followed by high performance liquid chromatography for the determination of three alkylphenols in environmental water samples

A simple, rapid and eco-friendly method named dispersive liquid-liquid microextraction based on solidification of floating organic drop (DLLME-SFO) was developed for the determination of 2-tert-butyl-4-ethylphenol, 4-tert-octylphenol and 2,4-di-tert-butylphenol in wastewater samples coupled with high performance liquid chromatography-ultraviolet detection (HPLC-UV).Octanoic acid was served as extraction solvent, and methanol was selected as dispersive solvent.The parameters affecting the extraction efficiency including the type and volume of the extraction solvents and the dispersive solvents, the pH and the salt addition were optimized.Under optimum conditions, the linear range was 20-1500 μg/L for all the three target alkylphenols.Limits of detection (LODs, S/N=3) were in the range of 0.45-0.61 μg/L.The enrichment factors (EFs) varied from 145 to 169, and the recoveries at three spiked levels were in the range of 80.1%-109.9%.It demonstrated that fatty acids including octanoic acid and nonanoic acid could be used as extraction solvent in DLLME-SFO method.The method is suitable for the determination of alkylphenols in environmental water samples.

Dispersive liquid-liquid microextraction based on solidification of floating organic drop and high-performance liquid chromatography to the analysis of cocaine's major adulterants in human urine.

A simple method has been proposed for the determination of cocaine's major adulterants (caffeine, levamisole, lidocaine, phenacetin, diltiazem, and hydroxyzine) in human urine by dispersive liquid-liquid microextraction based on solidification of floating organic drop (DLLME-SFO) in combination with high-performance liquid chromatography - photodiode array detector (HPLC-PDA). The reversed-phase chromatographic separation was obtained with a column C18 extended (250×4.6mm; 5μm; 80Å) in gradient elution mode using acetonitrile-trifluoroacetic acid 0.026% (v,v) (pH=2.5) at 1mLmin-1 as mobile phase, at 25°C, and detection at 235nm. The analysis time was 25min. This condition had the best resolution factors (>1.15), retention factors (>0.68), number of plates (>2094.9), and separation factors (>1.05) for all targets, indicating a good separation. The kind of extraction and dispersive solvent were investigated for unifactorial design. The buffer pH, the volume of extraction and disperser solvent, and the amount of salt were optimized for full factorial design. Under optimum conditions, human urine samples were alkalized with 0.5M sodium phosphate buffer (pH 10) and added to sodium chloride (20%m/v). Acetonitrile (150μL) and 1-dodecanol (30μL) were used as dispersive and extraction solvent, respectively. The method presented linear range of 312.5-3125ngmL-1 to caffeine and levamisole and 187.5-1875ngmL-1 to lidocaine, phenacetin, diltiazem, and hydroxyzine. The limit of quantification was 187.5ngmL-1 to lidocaine, phenacetin, diltiazem, and hydroxyzine and 312.5ngmL-1 for caffeine and levamisole. The recovery mean values were between 6.0 and 42.6%. The method showed good precision and accuracy, with within- and between-run relative standard deviation and relative error less than 15%. The samples were stable after freeze-thaw cycle and short-term room temperature stability tests. Besides, this method was satisfactorily applied in urine of cocaine users. It is expected that this method, which was the first to combine the use of DLLME-SFO and HPLC-PDA for the determination of cocaine's major adulterants in human urine, will contribute to the accuracy in the diagnosis of acute intoxication, the proper planning of therapeutic measures, as well as to the favorable prognostic of cocaine intoxicated patients.

Combination of counter current salting-out homogenous liquid-liquid extraction and dispersive liquid-liquid microextraction as a novel microextraction of drugs in urine samples.

The counter current salting-out homogenous liquid-liquid extraction (CCSHLLE) joined with the dispersive liquid-liquid microextraction based on solidification of floating organic drop (DLLME-SFO) has been developed as a high preconcentration technique for the determination of different drugs in urine samples. Amphetamines were employed as model compounds to assess the extraction procedure and were determined by high performance liquid chromatography-ultraviolet detection (HPLC-UV). In this method, initially, NaCl as a separation reagent is filled into a small column and a mixture of urine and acetonitrile is passed through the column. By passing the mixture, NaCl is dissolved and the fine droplets of acetonitrile are formed due to salting-out effect. The produced droplets go up through the remained mixture and collect as a separated layer. Then, the collected acetonitrile is removed with a syringe and mixed with 30.0μL 1-undecanol (extraction solvent). In the second step, the 5.00mLK2CO3 solution (2% w/v) is rapidly injected into the above mixture placed in a test tube for further DLLME-SFO. Under the optimum conditions, calibration curves are linear in the range of 1-3000μgL(-1) and limit of detections (LODs) are in the range of 0.5-2μgL(-1). The extraction recoveries and enrichment factors ranged from 78 to 84% and 157 to 168, respectively. Repeatability (intra-day) and reproducibility (inter-day) of method based on seven replicate measurements of 100μgL(-1) of amphetamines were in the range of 3.5-4.5% and 4-5%, respectively. The method was successfully applied for the determination of amphetamines in the actual urine samples. The relative recoveries of urine samples spiked with amphetamine and methamphetamine are 90-108%.

Determination of Methadone in Human Urine Using Salting-Out Effect and Dispersive Liquid-Liquid Microextraction Followed by HPLC-UV

The salting-out effect combined with the dispersive liquid-liquid microextraction based on solidification of floating organic drop (DLLME-SFO) has been developed as a high preconcentration technique for the determination of drug in urine samples. Methadone was employed as model compound to assess the extraction procedure and were determined by high performance liquid chromatography-ultraviolet detection (HPLC-UV). In this method, initially, NaCl as a separation reagent is filled into a small column and a mixture of urine and acetonitrile is passed through the column. By passing the mixture, NaCl is dissolved and the fine droplets of acetonitrile are formed due to saltingout effect. The produced droplets go up through the remained mixture and collect as a separated layer. Then, undecanol (extraction solvent). In the second step, the 5.00 mL K2CO3 solution (2% w/v) is rapidly injected into the above mixture placed in a test tube for further DLLME-SFO. Under the optimum conditions, calibration curves are linear in the range of 2-2000 μg L-1 and limit of detection (LOD) is 0.7 μg L-1. the collected acetonitrile is removed with a syringe and mixed with 30.0 μL-1 .The extraction recovery and enrichment factor were 83% and 140%, respectively. Repeatability (intra-day) and reproducibility (inter-day) of method based on seven replicate measurements of 100 μg L-1 of methadone were 4.1% and 5.3%, respectively. The relative recoveries of urine samples spiked with methadone are 92%-106%.

Sensitive analysis In(III) in various matrices by spectrophotometry after dispersive liquid-liquid microextraction based on solidification of floating organic drop

A dispersive liquid-liquid microextraction based on solidification of floating organic drop (DLLME-SFOD) was developed for preconcentration and determination of indium in real samples. In this method, an appropriate mixture of acetone (as disperser solvent) and 1-undecanol (as extracting solvent) containing dithizone (as chelating agent) was rapidly injected into the aqueous samples of indium. In this step, the cloudy solution was formed and the complexes of In-dithizone was extracted into 1-undecanol. After the phase separation, the absorbance of the extracted indium was measured at 510 nm. Under the optimum condition, the calibration graph was linear in the range of 30–230 μg L−1 with detection limit of 9 μg L−1. The relative standard deviation (RSD, n = 6) was 1.04 %. The developed method was successfully applied to extract and determine indium in real samples.

Preconcentration of organochlorine pesticides in aqueous samples by dispersive liquid-liquid microextraction based on solidification of floating organic drop after SPE with multiwalled carbon nanotubes

SPE joined with dispersive liquid-liquid microextraction based on solidification of floating organic drop (DLLME-SFO) as a novel technique combined with GC with electron-capture detection has been developed as a preconcentration technique for the determination of organochlorine pesticides (OCPs) in water samples. Aqueous samples were loaded onto multiwalled carbon nanotubes as sorbent. After the elution of the desired compounds from the sorbent by using acetone, the DLLME-SFO technique was performed on the obtained solution. Variables affecting the performance of both steps such as sample solution flow rate, breakthrough volume, type and volume of the elution, type and volume of extraction solvent and salt addition were studied and optimized. The new method provided an ultra enrichment factor (8280-28221) for nine OCPs. The calibration curves were linear in the range of 0.5-1000 ng/L, and the LODs ranged from 0.1-0.39 ng/L. The RSD, for 0.01 μg/L of OCPs, was in the range of 1.39-13.50% (n = 7). The recoveries of method in water samples were 70-113%.

Separation/preconcentration and determination of quercetin in food samples by dispersive liquid-liquid microextraction based on solidification of floating organic drop -flow injection spectrophotometry.

A new dispersive liquid-liquid microextraction based on solidification of floating organic drop (DLLME-SFOD)-flow injection spectrophotometry (FI) method for the separation and preconcentration of trace amounts of quercetin was developed. 1-Undecanol and methanol was used as the extraction and disperser solvent, respectively. The factors influencing the extraction by DLLME-SFOD such as the volume of the extraction and disperser solvents, pH and concentration of salt were optimized. The optimal conditions were found to be; volume of the extraction solvent, 80μL; the volume of the disperser solvent, 100μL; and the pH of the sample, 3. The linear dynamic range and detection limit were 5.0 × 10(-8)-5.0 × 10(-7)molL(-1) and 1 × 10(-8)molL(-1), respectively. The relative standard deviation (R.S.D.) at 6.1 × 10(-8)molL(-1) level of quercetin (n = 10) was found to be 2.8%. The method was successfully applied to the determination of quercetin in the apple, grape, onion and tomato samples. Figureᅟ

Dispersive liquid–liquid microextraction based on solidification of floating organic drop combined with field‐amplified sample injection in capillary electrophoresis for the determination of beta(2)‐agonists in bovine urine

Dispersive liquid-liquid microextraction based on solidification of floating organic drop (DLLME-SFO) was for the first time combined with field-amplified sample injection (FASI) in CE to determine four β(2)-agonists (cimbuterol, clenbuterol, mabuterol, and mapenterol) in bovine urine. Optimum BGE consisted of 20 mM borate buffer and 0.1 mM SDS. Using salting-out extraction, β(2)-agonists were extracted into ACN that was then used as the disperser solvent in DLLME-SFO. Optimum DLLME-SFO conditions were: 1.0 mL ACN, 50 μL 1-undecanol (extraction solvent), total extraction time 1.5 min, no salt addition. Back extraction into an aqueous solution (pH 2.0) facilitated direct injection of β(2)-agonists into CE. Compared to conventional CZE, DLLME-SFO-FASI-CE achieved sensitivity enhancement factors of 41-1046 resulting in LODs in the range of 1.80-37.0 μg L(-1). Linear dynamic ranges of 0.15-10.0 mg L(-1) for cimbuterol and 15-1000 μg L(-1) for the other analytes were obtained with coefficients of determination (R(2)) ≥ 0.9901 and RSD% ≤5.5 (n = 5). Finally, the applicability of the proposed method was successfully confirmed by determination of the four β(2)-agonists in spiked bovine urine samples and accuracy higher than 96.0% was obtained.

Trace mercury determination in drinking and natural water after preconcentration and separation by DLLME-SFO method coupled with cold vapor atomic absorption spectrometry

A novel dispersive liquid–liquid microextraction based on solidification of floating organic drop (DLLME-SFO) for simultaneous separation/preconcentration of ultra trace amounts of mercury was used. A method based on amalgamation was used for collection of gaseous mercury on gold coated sand (Gold trap). The concentration of mercury was determined by cold vapor atomic absorption spectrometry (CV-AAS). The DLLME-SFO behavior of mercury by using dithizone as complexing agent was systematically investigated. The factors influencing, the complex formation and extraction of DLLME-SFO method such as type and volume of extraction and disperser solvents, pH, concentration of salt, centrifuging time and concentration of the chelating agent were optimized. The method was successfully applied to the determination of mercury in drinking and natural water and satisfactory relative recoveries (95–105%) were achieved. The proposed procedure was based on very low consumption of organic solvents. The other benefits of the system were sensitive, simple, friendly to the environment, rejection of matrix constituent, low cost, the time consuming and high enrichment factor.

Determination of copper in human hair and tea samples after dispersive liquid-liquid microextraction based on solidification of floating organic drop (DLLME-SFO)

A simple method of dispersive liquid-liquid microextraction-solidified floating organic drop (DLLME-SFO) prior to flame atomic absorption spectrometry was successfully used for separating and preconcentrating copper in human hair and tea samples. The proposed method was simple, cheap, and has high precision. In this study, optimization of experimental parameters influencing the extraction, such as type and volume of extraction and disperser solvents, pH, the amount of chelating agent and extraction time was normally carried out using a step-by-step approach, in which each factor was varied sequentially. The effect of the interfering ions on the analytes recovery was also investigated. The calibration graph was linear in the range of 5-200 ng mL-1 with limit of detection of 3.4 ng mL-1. The relative standard deviation (RSD) was 0.7% (n = 10, C = 2 ng mL-1) and the enhancement factor was 28.

Rapid determination of anilines in water samples by dispersive liquid–liquid microextraction based on solidification of floating organic drop prior to gas chromatography–mass spectrometry

A rapid, sensitive and environmentally friendly method for the analysis of 14 anilines in water samples by dispersive liquid-liquid microextraction based on solidification of floating organic drop (DLLME-SFO) prior to gas chromatography-mass spectrometry (GC-MS) was developed and optimized. In the proposed method, cyclohexane was used as the extraction solvent as its toxicity was much lower than that of the solvent usually used in dispersive liquid-liquid microextraction (DLLME). In the optimized conditions, the method exhibited good analytical performance. Based on a signal-to-noise ratio of 3, limits of detection for anilines were in the range of 0.07 to 0.29 μg L(-1), and the linear range was 0.5-200 μg L(-1) with regression coefficients (r(2)) higher than 0.9977. It was efficient for qualitative and quantitative analysis of anilines in water samples. The relative standard deviations varied from 2.9 to 8.6% depending on different compounds indicating good precision. Tap water and river water were selected for evaluating the application to real water samples. The relative recoveries of anilines for the two real samples spiked with 10 μg L(-1) anilines were in the scope of 78.2-114.6% and 77.3-115.6%, respectively.

Dispersive Liquid-Liquid Microextraction Based on Solidification of Floating Organic Drop Followed by Gas Chromatography-Electron Capture Detector for Determination of Some Pesticides in Water Samples

In this study dispersive liquid-liquid microextraction based on solidification of floating organic drop (DLLME-SFO) followed by gas chromatography-electron capture detection (GC-ECD) was developed for determination of some pesticides in the water samples. Some important parameters, such as type and volumes of extraction and disperser solvent and salt effect on the extraction recovery of analytes from aqueous solution were investigated. Under the optimum conditions (extraction solvent: 1-undecanol, 15.0 μL; disperser solvent: acetone, 1.0 mL, and without salt addition), the preconcentration factors were obtained ranged from 802 to 915 for analytes. The linear ranges were from 0.05 to 100 μg L−1, and detection limits ranged from 0.05 to 0.008 μg L−1. The relative standard deviations (RSDs%, ) were between 3.2% and 6.7%. The proposed method was successfully applied to the determination of target analytes in the tap, sea, and river water samples, and satisfactory recoveries were obtained.

Spectrophotometric determination of iron species using a combination of artificial neural networks and dispersive liquid–liquid microextraction based on solidification of floating organic drop

A dispersive liquid–liquid microextraction based on solidification of floating organic drop (DLLME-SFO) and artificial neural networks method was developed for the simultaneous separation/preconcentration and speciation of iron in water samples. In this method, an appropriate mixture of ethanol (as the disperser solvent) and 1-undecanol (as the extracting solvent) containing appropriate amount of 2-thenoyltrifluoroacetone (TTA) (as the complexing agent) was injected rapidly into the water sample containing iron (II) and iron (III) species. At this step, the iron species interacted with the TTA and extracted into the 1-undecanol. After the phase separation, the absorbance of the extracted irons was measured in the wavelength region of 450–600nm. The artificial neural networks were then applied for simultaneous determination of individual iron species. Under optimum conditions, the calibration graphs were linear in the range of 95–1070μgL−1 and 31–350μgL−1 with detection limits of 25 and 8μgL−1 for iron (II) and iron (III), respectively. The relative standard deviations (R.S.D., n=6) were lower than 4.2%. The enhancement factor of 162 and 125 were obtained for Fe3+ and Fe2+ ions, respectively. The procedure was applied to power plant drum water and several potable water samples; and accuracy was assessed through the recovery experiments and independent analysis by graphite furnace atomic absorption spectrometry.

A novel method for the determination of trace copper in cereals by dispersive liquid–liquid microextraction based on solidification of floating organic drop coupled with flame atomic absorption spectrometry

Abstract A novel, simple, rapid, efficient and environment-friendly method for the determination of trace copper in cereal samples was developed by using dispersive liquid–liquid microextraction based on solidification of floating organic drop (DLLME-SFO) followed by flame atomic absorption spectrometry. In the DLLME-SFO, copper was complexed with 8-hydroxy quinoline and extracted into a small volume of 1-dodecanol, which is of low density, low toxicity and proper melting point near room temperature. The experimental parameters affecting the extraction efficiency were investigated and optimized. Under the optimum conditions, the calibration graph exhibited linearity over the range of 0.5–500 ng/mL with the correlation coefficient ( r ) of 0.9996. The enrichment factor was 122 and the limit of detection was 0.1 ng/mL. The method was applied to the determination of copper in the complex matrix samples such as rice and millet with the recoveries for the spiked samples at 5.0 and 10.0 μg/g falling in the range of 92.0–98.0% and the relative standard deviation of 3.9–5.7%.

Separation/preconcentration and determination of vanadium with dispersive liquid–liquid microextraction based on solidification of floating organic drop (DLLME-SFO) and electrothermal atomic absorption spectrometry

A novel dispersive liquid–liquid microextraction based on solidification of floating organic drop (DLLME-SFO) for separation/preconcentration of ultra trace amount of vanadium and its determination with the electrothermal atomic absorption spectrometry (ETAAS) was developed. The DLLME-SFO behavior of vanadium (V) using N-benzoyl-N-phenylhydroxylamine (BPHA) as complexing agent was systematically investigated. The factors influencing the complex formation and extraction by DLLME-SFO method were optimized. Under the optimized conditions: 100 μL, 200 μL and 25 mL of extraction solvent (1-undecanol), disperser solvent (acetone) and sample volume, respectively, an enrichment factor of 184, a detection limit (based on 3S b/m) of 7 ng L −1 and a relative standard deviation of 4.6% (at 500 ng L −1) were obtained. The calibration graph using the preconcentration system for vanadium was linear from 20 to 1000 ng L −1 with a correlation coefficient of 0.9996. The method was successfully applied for the determination of vanadium in water and parsley.