Combination Of Dispersive Liquid-liquid Microextraction Research Articles

Trace nickel determination in seawater matrix using combination of dispersive liquid-liquid microextraction and triethylamine-assisted Mg(OH)2 method.

In order to eliminate the effects of seawater matrix on the precise/accurate determination of elements, new and efficient analytical procedure requires. In this study, co-precipitation method based on the triethylamine (TEA)-assisted Mg(OH)2 was performed to eliminate side-effects of seawater medium on the determination with flame atomic absorption spectrometry (FAAS) prior to the preconcentration of nickel by an optimized dispersive liquid-liquid microextraction (DLLME) method. Under the optimum conditions of the presented method, the limit of detection and quantification (LOD, LOQ) values obtained for nickel were found as 16.1 and 53.8μgkg-1, respectively. Seawater samples collected from West Antarctic region were used for real sample applications to check the accuracy and applicability of developed method, and satisfying recovery results (86-97%) were obtained. In addition to this, the digital image-based colorimetric detection system and the UV-Vis system were applied to confirm the applicability of the developed DLLME-FAAS method in other analytical systems.

A simple and rapid determination of Al(III) in natural water samples using dispersive liquid-liquid microextraction after complexation with a novel antipyrine-based Schiff base reagent.

The purpose of this study is the development of a novel strategy for the determination of Al3+ ions using the combination of dispersive liquid-liquid microextraction(DLLME)andUV-Vis spectrophotometry. The method is grounded in the complexation between a novel antipyrine-based Schiff base reagent (EHMP) and Al3+ ions. Aluminum concentrations were detected using UV-Vis spectrophotometry at 260nm and this technique was optimized using the absorbance value of EHMP-Al complex. pH, mixing period, type and volume of organic solvent, etc. were optimized stepwise in order to find out optimum experimental conditions. The limit of detection and the limit of quantification values for the improved analytical method were to be estimated 0.31 and 1.03μmol.L-1, respectively. The new strategy was successfully performed to define Al3+ ions in natural water samples with RSD values (84.01-107.71%) and recovery values (0.01-0.09%).

Ultrasound-assisted dispersive liquid antisolvent precipitation for extraction of polar organic compounds in water

This paper reports on the development of an extraction method called “ultrasound-assisted dispersive liquid antisolvent precipitation (UA-DLAP)”. The developed method is a combination of dispersive liquid-liquid microextraction (DLLME) and liquid antisolvent precipitation (LAP) methods. Unlike DLLME, the extraction solvent in UA-DLAP is replaced with a bad solvent for the analyte which has a low affinity toward the analyte (antisolvent). Unlike LAP, in UA-DLAP the analyte is dissolved in water, the antisolvent is water-immiscible and denser than water, and the needed volume of the antisolvent is in microliter range. In UA-DLAP, after the addition of a mixture of the antisolvent and a disperser solvent to the sample solution under sonication, a cloudy mixture containing the antisolvent micro/nanodroplets appears. After centrifugation of the mixture, three phases appear (a water-rich phase in the top, an analyte rich precipitate phase in middle, and an antisolvent rich phase in the bottom). Finally, the analyte rich precipitate phase is separated and dissolved in a back-extraction solvent. To evaluate the efficiency of the UA-DLAP method and its possible mechanism of action, three model polar organic compounds in water were extracted by UA-DLAP and determined spectrophotometrically. The results showed that the precipitate phase for all of the investigated analytes was nanostructured. The limits of detection were 22 ng mL−1, 11 ng mL−1, and 3.9 ng mL−1 for doxorubicin, methylene blue, and Congo red, respectively. Respective experimental enrichment factors were 18.3, 27.8, and 31.1.

Combination of dispersive liquid-liquid microextraction using multifunctional ionic liquids with high performance chromatography for determination of phthalate ester metabolites in human urine sample

A novel sensitive method for the determination of the five primary metabolites of phthalate esters (PAEs) in urine was developed by combining dispersive liquid-liquid microextraction (DLLME) using ionic liquids with high performance liquid chromatography (HPLC). The factors affecting the efficiency of DLLME were optimized. The types and proportions of extraction solvent and dispersants, as well the ultrasonic extraction time, cooling time, and centrifugal time, were determined. The optimal conditions were as follows:extraction solvent[C8MIM]PF6] 35 μL; dispersants[BSO3HMIm]OTf] 30 μL,[C4MIM]BF6] 120 μL; NH4PF6 0.1 g, extraction at 35℃, ultrasonic dispersion for 5 min, cooling in ice water for 5 min, centrifugation at 4000 r/min for 5 min. After optimization, the five primary metabolites of PAEs were determined. The method showed a good linear relationship within the concentration range of 0.5-1000 μg/L. The determination coefficients (R2) were greater than 0.9955. The detection limit was in the range of 0.16-0.19 μg/L. Under the optimized conditions, the extraction recoveries for the PAEs were 92.9%-105.0%, and the relative standard deviations (RSDs) of the intra- and inter-day precisions were < 5.96%. Urine samples collected from 10 diabetic patients were tested, and the exposure level of the population to the PAE metabolites was evaluated. All the PAE metabolites were detected in these samples, and the detection rate of 2-ethylhexyl hydrogen phthalate (MEHP) was 100%. In conclusion, no toxic organic reagents were added during the extraction process in this method, and multifunctional ionic liquids were used as the extraction agent, dispersant, and salting-out agent. In other words, the extraction process was demonstrated to be green, simple, and efficient. The developed method has high sensitivity and stability, and it is suitable for the determination of trace PAE metabolites in human urine.

Application of dispersive liquid-liquid microextraction and GC–MS/MS for the determination of GHB in beverages and hair

Recently, gamma-hydroxybutyrate (GHB) was determined in “Kawa Trendy Drink” which was labeled as a functional beverage containing gamma-aminobutyric acid and quickly became popular in various club in China. GHB has a strong sedative effect and is often used as a date rape drug and euphoriant in drug-facilitated sexual assaults. However, it is believed that same beverages themselves contain natural GHB. Whether GHB contained in seized beverages was added or exists in themselves resulted in complicated interpretation of the nature of cases. The detection window of GHB in blood (5 h) and urine (<12 h) was narrow, make documentation of GHB exposure difficult, while hair can extend the detection time of GHB from several hours to several days/months. Thus, a sensitive detection method based on dispersive liquid-liquid microextraction (DLLME) and GC–MS/MS for GHB in beverages and hair had been established. Under the optimum extraction conditions, acceptable linear relationship was achieved in the range of 1.5–500 ng/mL with the correlation coefficient (r) of 0.9986 for spiked water samples and in the range of 0.03–10 ng/mg with the correlation coefficient (r) of 0.9979 for spiked melanin samples. The LOD (S/N = 3) was estimated to be 0.5 ng/mL and 0.01 ng/mg, respectively. A recovery of 70.6–88.5% were obtained for spiked samples. The mean relative error (MRE) was within ±6.5% and the relative standard error (RSD) was less than 4.9%. The combination of DLLME with GC–MS/MS offers an alternative analytical approach for the sensitive detection of GHB in real beverages sold in Chinese markets and in hair of Chinese population for forensic purposes. The proposed methods had the advantages of shorter extraction time and were suitable for simultaneous pretreatment of samples in batches. To our knowledge, this is the first report to present GHB in beverages and human hair using DLLME.

Dispersive liquid–liquid microextraction coupled with graphite furnace atomic absorption spectrometry for determination of trace cobalt in environmental water samples

ABSTRACT A highly sensitive, simple and rapid method was developed for the determination of ultra-trace cobalt by dispersive liquid-liquid microextraction (DLLME) combined with graphite furnace atomic absorption spectrometry (GFAAS). The combination of DLLME and GFAAS methods is favourable for GFAAS is a well-established technique with excellent sensitivity, and is suitable for low volume of sample of the remained phase obtained after DLLME. For DLLME, a newly synthesised reagent 5-(5-Cyano-2-pyridylazo)-2,4-diaminotoluene (5-CN-PADAT) was used as a chelating agent, 1,2-dichloroethane (CH2ClCH2Cl) and acetonitrile (CH3CN) as extraction and dispersive solvent. Several variables potentially affecting the extraction efficiency and its subsequent determination, such as type and volume of extraction and disperser solvents, pH of test solution, extraction time, volume and concentration of the chelating agent and salt effect, were investigated and optimised. After phase separation, 10 µL of the sedimented phase containing enriched analytes was injected into GFAAS for the determination of cobalt. Under the optimised conditions, the analytical graph was linear in the range of 0.04 ~ 1.0 ng mL−1, and the limit of detection was 0.01 ng L−1 for cobalt. The relative standard deviation (RSD) for 10 replicate measurements of 0.2 ng L−1 of cobalt was 3.6%. Enrichment factor (EF) calculated as the ratio of the slopes of the calibration graphs obtained with and without DLLME was 96 for 5.0 mL sample solution. The method was successfully applied to the determination of trace cobalt in water samples with satisfactory results.

Thin film nanofibers containing ZnTiO3 nanoparticles for rapid evaporation of extraction solvent: application to the preconcentration of chlorpyrifos prior to its quantification by ion mobility spectrometry.

Thin film nanofibers containing ZnTiO3 nanoparticles were used for rapid and efficient evaporation of solvents as used to extract analytes by dispersive liquid-liquid microextraction (DLLME). The method is referred to as thin film evaporation (TFE). A combination of DLLME and TFE was applied to the extraction and preconcentration of the pesticide chlorpyrifos (as a model compound) prior to analysis by ion mobility spectrometry. The ZnTiO3 nanoparticles were placed on polyacrylonitrile nanofibers which increases the porosity and surface area in the TFE process, thus causing fast and complete evaporation of solvents. The effects of sample pH value, extraction solvent and its volume, disperser solvent and volume, centrifugation time, evaporation time, and desorption temperature were optimized. The relative standard deviations of intra- and inter-day analyses were found to be 3% and 7%, respectively. The method has a linear dynamic range that covers the 0.10-3.0μg.L-1 chlorpyrifos concentration range, the limit of detection is 0.04μg.L-1, and the enrichment factor is up to 5400 in case of spiked samples. Some spiked field samples were analyzed and the relative recoveries ranged between 99 and 111%. When applied along with ion mobility spectrometry, the interferences caused by solvent are found to be reduced in the ionization source. This makes it possible to select a variety of solvents as needed for sample extraction. Graphical abstract Schematic presentation of dispersive liquid-liquid microextraction (DLLME) combined with thin film evaporation (TFE) for rapid vaporization of extraction solvent: Application to the pre-concentration of chlorpyrifos prior to its quantification by corona discharge-ion mobility spectrometry (CD-IMS).

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

A combination of dispersive liquid-liquid microextraction and surface plasmon resonance sensing of gold nanoparticles for the determination of ziram pesticide.

We have developed a reliable, fast, and highly sensitive analytical method utilizing dispersive liquid-liquid microextraction and gold nanoparticles probes for ziram (zinc bis(dimethyldithiocarbamate)) determination. The method is based on the in situ formation of gold nanoparticles in carbon tetrachloride as an organic phase. It was found that the trace levels of ziram influenced the formation of gold nanoparticles, leading to absorbance change of a sedimented phase. The results of the colorimetric ziram determination were in the concentration range of 0.12-2.52ng/mL with a limit of detection of 0.06ng/mL. The formation of the stable and dispersed gold nanoparticles in the organic phase provides a good precision for dispersive liquid-liquid microextraction method, resulting in the relative standard deviation of 3.8 and 1.2% for 0.56 and 1.58ng/mL of ziram, respectively. This method has been successfully used for the ziram determination in samples of well and river water, soil, potato, carrot, wheat, and paddy soil.

Combination of dispersive liquid-liquid microextraction based on ionic liquid and pre-column fluorescence derivatization-high performance liquid chromatography for determination of eight sulfonamides in water samples

Dispersive liquid-liquid microextraction based on ionic liquid coupled with high performance liquid chromatography (HPLC) and pre-column fluorescent derivatization method (IL-DLLME-HPLC-FL) was developed for the determination of eight sulfonamides (SAs). The influence of IL-DLLME parameters on extraction efficiency and the stability of derivatives of the eight SAs were investigated. The optimized experimental conditions were as follows: 40 µL [C6MIM][PF6] as extraction solvent, 0.1 mL acetone as dispersion solvents; water sample with 0% NaCl (pH 4) was extracted by dispersive liquid-liquid microextraction without ultrasonic-assistance and then derivatized for 6 h. Under the optimized experimental conditions, the results indicated that the eight sulfanilamides showed good linearities when their mass concentrations were in 0. 2-10 µg/L and 10-500 µg/L, and the linear correlation coefficients were no less than 0. 9989. The detection limits ranged from 0. 08 µg/L to 0. 5 µg/L (S/N=3). The proposed method was applied to the analysis of four water samples from different sources (tap water, lake water, Pearl River water and pond water). The relative recoveries of the SAs spiked in water samples were 87. 2% - 101. 4% with the relative standard deviations of 3. 7% - 6. 2% at three different concentration levels of 5, 50 and 200 µg/L. It is a convenient, environmental friendly method for the routine analysis of SAs in water samples.

Recent developments in dispersive liquid–liquid microextraction

During the past 7 years and since the introduction of dispersive liquid-liquid microextraction (DLLME), the method has gained widespread acceptance as a simple, fast, and miniaturized sample preparation technique. Owing to its simplicity of operation, rapidity, low cost, high recovery, and low consumption of organic solvents and reagents, it has been applied for determination of a vast variety of organic and inorganic compounds in different matrices. This review summarizes the DLLME principles, historical developments, and various modes of the technique, recent trends, and selected applications. The main focus is on recent technological advances and important applications of DLLME. In this review, six important aspects in the development of DLLME are discussed: (1) the type of extraction solvent, (2) the type of disperser solvent, (3) combination of DLLME with other extraction methods, (4) automation of DLLME, (5) derivatization reactions in DLLME, and (6) the application of DLLME for metal analysis. Literature published from 2010 to April 2013 is covered.

Dispersive liquid–liquid microextraction using diethyldithiocarbamate as a chelating agent and the dried-spot technique for the determination of Fe, Co, Ni, Cu, Zn, Se and Pb by energy-dispersive X-ray fluorescence spectrometry

Dispersive liquid–liquid microextraction (DLLME) using sodium diethyldithiocarbamate (DDTC) as a chelating agent was investigated for the simultaneous determination of iron, cobalt, nickel, copper, zinc, selenium and lead ions in water samples. The procedure was performed using 5mL of the sample, 100μL of a 0.5% solution of DDTC, 30μL of carbon tetrachloride (extraction phase) and 500μL of methanol (disperser solvent). The experiments showed that Fe, Co, Ni, Cu, Zn and Pb can be simultaneously extracted at a pH of 5 and that Se can be extracted at a pH of 2–3. The results were compared with those obtained using ammonium pyrrolidine dithiocarbamate as a chelating agent. For all analytes, a linear range was observed up to 0.4μgmL−1. If Fe and Zn are present in concentrations 10 times higher than those of the other analytes, then the linearity is observed up to 0.2μgmL−1. In the present study, the organic phase that contained preconcentrated elements was deposited onto a Millipore filter and measured using energy-dispersive X-ray fluorescence spectrometry. The obtained detection limits were 2.9, 1.5, 2.0, 2.3, 2.5, 2.0 and 3.9ngmL−1 for Fe, Co, Ni, Cu, Zn, Se and Pb, respectively. This combination of DLLME and the dried-spot technique is promising for multielement analyses using other spectroscopy techniques, such as laser ablation‐inductively coupled plasma‐mass spectrometry, laser-induced breakdown spectroscopy or total-reflection X-ray fluorescence spectrometry.

Dispersive liquid–liquid microextraction combined with capillary electrophoresis and time-of-flight mass spectrometry for urine analysis

The combination of dispersive liquid–liquid microextraction (DLLME) with capillary electrophoresis (CE) and a time-of-flight mass spectrometer (TOF-MS) was evaluated for the toxicological screening in urine samples. A methodology based on design of experiments (DOE) was implemented to increase the extraction efficiency. Dichloromethane and isopropanol were selected as the extraction and dispersing solvents, respectively. Seven factors for DLLME were screened with the help of a Plackett–Burmann DOE using two model compounds before fine investigation of the important parameters to maximise the compound extraction. These experiments were performed in the CE-UV configuration to overcome potential MS matrix effects. The performance of the entire procedure was then evaluated using CE-ESI-TOF-MS. With a preconcentration factor of more than 130, the highly sensitive DLLME-CE-ESI-TOF-MS method allowed for the detection of 30 toxicological compounds (i.e., amphetamines and their derivatives, opiates, cocaine and its metabolites and pharmaceuticals) in urine with limits of detection in the sub-ng/mL level and was used to analyse real toxicological samples. The combination of DLLME and CE was particularly attractive because of the small amount of organic solvents required.

Background corrected dispersive liquid-liquid microextraction of cadmium combined with flame atomic absorption spectrometry

A new procedure was developed for dispersive liquid-liquid micro extraction of cadmium prior to its determination by flame atomic absorption spectrometry. The major difficulty in combination of dispersive liquid-liquid microextraction with flame atomic absorption spectrometry is high background absorption of the extraction and disperser solvents that covers the absorbance of analyte. The background absorption was removed by changing the solvent of sedimented phase from organic to aqueous. In the proposed approach, tetrachloroethylene (C2Cl4) and tetrahydroforan (THF) were used as extraction and dispersive solvents respectively. Dithizone was used as complexing agent. Several factors that may be affect on the extraction process, such as, extraction solvent, disperser solvent, the volume of extraction and disperser solvent, extraction time, temperature of solution, concentration of chelating agent and pH were optimized. The effects of common coexisting ions on the recovery of cadmium were studied. Results showed that cadmium recoveries are almost quantitative in the presence of interfering ions. Under the optimal conditions the enrichment and enhancement factors were 34.5 and 26 respectively, the extraction and relative recoveries were 69% and 99% respectively, the calibration graph was linear in the range of 5-150 µg L-1, the detection limit was 1.2 µg L-1 and the relative standard deviation (n = 8) was 2.1%. The proposed method was applied successfully for determination of trace amounts of cadmium in water samples