Dispersive Liquid-liquid Microextraction Method Research Articles

A sensing colorimetric method based on in situ formation of gold nanoparticles after dispersive liquid-liquid microextraction for determination of zineb

A novel and highly efficient dispersive liquid–liquid microextraction (DLLME) based on the use of gold nanoparticles (AuNPs) plasmon resonance was developed for the determination of trace amounts of zineb pesticide. The label-free AuNPs as colorimetric probes were synthesized in situ into organic phase using a simple and rapid DLLME procedure. The presence of zineb affected on the plasmon absorbance of AuNPs in sedimented phase which allows the microvolume spectrophotometric sensing of this pesticide. Under the optimal conditions, the method is capable of determining zineb over a range of 0.8–20.0ngmL−1 with a limit of detection 0.55ngmL−1. The formation of the stable and dispersed AuNPs in organic phase provides a good precision for suggested DLLME method resulting in the relative standard deviation of 4.6 and 1.0% for 8 and 16ngmL−1 of zineb, respectively. The method was also successfully applied to the determination of zineb in the environmental samples with the recoveries in the range of 95.6–101.0% for the spiked samples.

Headspace single drop microextraction versus dispersive liquid-liquid microextraction using magnetic ionic liquid extraction solvents

A headspace single drop microextraction (HS-SDME) method and a dispersive liquid-liquid microextraction (DLLME) method were developed using two tetrachloromanganate ([MnCl42-])-based magnetic ionic liquids (MIL) as extraction solvents for the determination of twelve aromatic compounds, including four polyaromatic hydrocarbons, by reversed phase high-performance liquid chromatography (HPLC). The analytical performance of the developed HS-SDME method was compared to the DLLME approach employing the same MILs. In the HS-SDME approach, the magnetic field generated by the magnet was exploited to suspend the MIL solvent from the tip of a rod magnet. The utilization of MILs in HS-SDME resulted in a highly stable microdroplet under elevated temperatures and long extraction times, overcoming a common challenge encountered in traditional SDME approaches of droplet instability. The low UV absorbance of the [MnCl42-]-based MILs permitted direct analysis of the analyte enriched extraction solvent by HPLC. In HS-SDME, the effects of ionic strength of the sample solution, temperature of the extraction system, extraction time, stir rate, and headspace volume on extraction efficiencies were examined. Coefficients of determination (R2) ranged from 0.994 to 0.999 and limits of detection (LODs) varied from 0.04 to 1.0μgL−1 with relative recoveries from lake water ranging from 70.2% to 109.6%. For the DLLME method, parameters including disperser solvent type and volume, ionic strength of the sample solution, mass of extraction solvent, and extraction time were studied and optimized. Coefficients of determination for the DLLME method varied from 0.997 to 0.999 with LODs ranging from 0.05 to 1.0μgL−1. Relative recoveries from lake water samples ranged from 68.7% to 104.5%. Overall, the DLLME approach permitted faster extraction times and higher enrichment factors for analytes with low vapor pressure whereas the HS-SDME approach exhibited better extraction efficiencies for analytes with relatively higher vapor pressure.

Determination of Natamycin in Dairy Products Using Dispersive Liquid-Liquid Microextraction and Indirect Flame Atomic Absorption Spectrometry

In this paper, a dispersive liquid-liquid microextraction method has been developed for the extraction and preconcentration of natamycin from cheese and doogh samples and its determination by indirect flame atomic absorption spectrometry. For this purpose, an appropriate mixture of a disperser solvent (ethanol) and an extraction solvent (1,1,2-trichloroethane) is rapidly injected into the samples and Zn2+ cation was added. During this process, natamycin-Zn complex is extracted into fine droplets of the extraction solvent. After centrifugation, the fine droplets of the extractant containing the complex are sedimented at the bottom of a tube with conical bottom. The sedimented phase is injected into the determination system via a home-made sample introduction system. Under the optimal conditions, the linear range was between 5 and 1000 ng mL−1. The limit of detection of the target analyte was obtained 1.8 ng mL−1. The relative recoveries obtained for the spiked cheese and doogh samples were between 86 and 98%. Moreover, the precision of the method was acceptable (<3.9%) in all spiked concentrations. Finally, the method was successfully applied to determine natamycin in cheese and doogh samples.

Ultrasound assisted dispersive liquid-liquid microextraction coupled with high performance liquid chromatography designated for bioavailability studies of felodipine combinations in rat plasma.

Felodipine (FLD), a calcium channel antagonist, is commonly prescribed for the treatment of hypertension either with Metoprolol (MET) or Ramipril (RAM) in two different drug combinations. FLD has high plasma protein binding ability affecting its extraction recoveries from plasma samples. Hence, a specific ultrasound assisted dispersive liquid-liquid microextraction (UA-DLLME) method coupled with HPLC using photodiode array detector was developed and validated for the simultaneous determination of FLD, MET and RAM in rat plasma after oral administration of these combinations. The factors affecting UA-DLLME were carefully optimized. In this study, UA-DLLME method could provide simple and efficient plasma extraction procedures with superior recovery results. Under optimum condition, all target drugs were separated within 13min. The validation procedures was carried out in agreement with US-FDA guidelines and shown to be suitable for anticipated purposes. Linear calibration ranges were obtained in the range 0.05-2.0μgmL-1 for FLD and MET and 0.1-2.0μgmL-1 for RAM with detection limits of 0.013-0.031μgmL-1 for all the studied drug combinations. The%RSD for inter-day and intra-day precisions was in range of 0.63-3.85% and the accuracy results were in the range of 92.13-100.5%. The validated UA-DLLME-HPLC method was successfully applied for the bioavailability studies of FLD, MET and RAM. The pharmacokinetic parameters were calculated for all the investigated drugs in rats after single-dose administrations of two different drug combinations. Although FLD was bioequivalent in the two formulations, a small increase in plasma levels of MET and RAM was found in the presence of FLD.

Determination of trace amount of cadmium using dispersive liquid-liquid microextraction-slotted quartz tube-flame atomic absorption spectrometry

This study was performed to develop a sensitive analytical method for the determination of cadmium by slotted quartz tube-flame atomic absorption spectrometry (SQT-FAAS) after dispersive liquid-liquid microextraction (DLLME). The parameters affecting the cadmium complex formation and its extraction output were optimized to obtain high extraction efficiency. These included the pH and amount of the buffer solution, and the concentration of the ligand. The DLLME method was comprehensively optimized based on the type and amount of extraction solvent, dispersive solvent and salt. The type and period of mixing needed for a more effective extraction was also investigated. In order to further improve the sensitivity for the determination of cadmium, the flame atomic absorption spectrometry was fitted with a slotted quartz tube to increase the residence time of cadmium atoms in the pathway of incident light from a hollow cathode lamp. The limits of detection and quantitation (LOD and LOQ) for the FAAS were found to be 42 and 140μgL−1, respectively. Under the optimum conditions, LOD and LOQ of the FAAS after DLLME were calculated as 1.3 and 4.4μgL−1, respectively. Combining both optimized parameters of the DLLME and SQT-FAAS gave 0.5 and 1.5μgL−1 as LOD and LOQ, respectively. Accuracy of the method was also checked using a wastewater certified reference material (EU-L-2), and the result was in good agreement with the certified value.

Dispersive Liquid-Liquid Microextraction Method for HPLC Determination of Phenolic Compounds in Wine

A fast and efficient dispersive liquid-liquid microextraction (DLLME) method was developed for extraction of phenolic compounds from red, rose, or white wine followed by HPLC determination in this study. After different extraction solvents and conditions were evaluated, the fastest and highest efficiency extraction of 12 phenolic compounds including gallic acid, protocatechuic acid, chlorogenic acid, catechin, vanillic acid, caffeic acid, syringic acid, epicatechin, p-coumaric acid, trans-ferulic acid, quercetin, and kaempferol was achieved by using 1000 μL of ethyl acetate as an extraction solvent and 500 μL of acetonitrile as a dispersive solvent. The mixtures of solvents were mixed with 1000 μL of wine sample for 10 s of extraction time. The extractions were carried out two times. Under the optimal condition, the extraction recoveries of 12 phenolic compounds were in a range from 76.56 to 137.74%. Meanwhile, the linearity, sensitivity, and precision of an optimized HPLC analysis method were evaluated. The results showed that each phenolic compound had a good regression coefficient (R 2). The limits of detections and quantifications for all the 12 compounds were at 0.001 to 0.133 and 0.004 to 0.433 mg/L, respectively. The relative standard deviations of intra- and inter-day determinations of the 12 compounds were below 6.58 and 4.11%, respectively. The results showed that the red wines had the highest concentration of total phenolic compounds (48.74–196.07 mg/L), followed by the rose wine (31.11 mg/L) and white wine (11.18–30.39 mg/L). Catechin was the dominant phenolic in all the wines (exception of wine sample W8) and ranged from 3.02 to 72.89 mg/L. In general, the developed dispersive liquid-liquid microextraction with HPLC analysis is a fast and efficient method to determine the phenolic compounds in wine.

An Application of Gas Chromatography-Mass Spectrometry (GC-MS) Fast Automated Scan/SIM Type (FASST) in Determining the Preservative Levels in Foods

The preservatives used in food products are strictly monitored and regulated. The present study aims to imply a sensitive and reliable analytical method to quantify two classes of preservatives (i.e. carboxylic acid and phenolic compounds) in food by means of gas chromatography-mass spectrometry (GC-MS), aimed at monitoring the products available within the local stores. Target analytes were derivatized via aqueous-phase isobutyl chloroformate-mediated reaction followed by dispersive liquid-liquid microextraction (DLLME) method. The quantity and quality determination of the studied samples were assured by performing FASST approach in a single run GC-MS analysis. The combination of standard addition method with sample dilution compensated the effect of sample matrix on the quantitative determination of the tested preservatives in the examined samples. The concentrations of sorbic acid (SA) were 210 μg/mL and 1000 μg/mL in soft drink and sauces samples, respectively. On the other hand, sodium benzoate (226 μg/mL) was only found in soft drink, whereas, no parabens were detected in any samples collected from the local stores.

Development of a Dispersive Liquid-Liquid Microextraction Method Combined with UV-Visible Spectrophotometry for Determination of Trace Aluminum(III) in Water, Wastewater, Food, Biological, and Pharmaceutical Samples.

A simple and sensitive method was proposed for the preconcentration of trace levels of Al(III) prior to its determination by spectrophotometry, based on dispersive liquid-liquid microextraction. The complexation of the Al(III) was performed by chelation with Eriochrome Cyanine R (ECR). In this method, cetyltrimethyl ammonium bromide (CTAB) as a dispersant was dissolved in chloroform as an extractant solvent, and then the solution was rapidly injected by a syringe into the samples containing Al(III), which had already been complexed by ECR at optimized pH. Various parameters were studied and optimized for a 10 mL sample volume. Under the optimum conditions, the LOD (3 times the SD of 10 replicate readings of the reagent blank) and the dynamic range of the calibration obtained were 0.2 ng mL-1 (7 nM) and 1.0-80.0 ng mL-1, respectively. The RSDs for eight replicate determinations of 10 and 60 ng mL-1 of Al(III) were 3.3 and 1.8%, respectively. This strategy was successfully applied to determine the Al concentration in water, wastewater, yogurt, apple, carrot, celery, bread, potato, urine, and Al-Mg syrup samples.

Coupling of homogeneous liquid-liquid extraction and dispersive liquid-liquid microextraction for the extraction and preconcentration of polycyclic aromatic hydrocarbons from aqueous samples followed by GC with flame ionization detection.

In the present study, a simple and rapid method for the extraction and preconcentration of some polycyclic aromatic hydrocarbons in water samples has been developed. In this method, two sample preparation methods were combined to obtain high extraction recoveries and enrichment factors for sensitive analysis of the selected analytes. In the first stage of the method, a homogeneous solution containing an aqueous solution and cyclohexyl amine is broken by the addition of a salt. After centrifugation, the upper collected phase containing the extracted analytes is subjected to the following dispersive liquid-liquid microextraction method. Rapid injection of the mixture of cyclohexyl amine resulted from the first stage and 1,1,2-trichloroethane (as an extraction solvent) into an acetic acid solution is led to form a cloudy solution. After centrifuging, the fine droplets of the extraction solvent are settled down in the bottom of the test tube, and an aliquot of it is analyzed by gas chromatography. Under the optimum extraction conditions, enrichment factors and limits of detection for the studied analytes were obtained in the ranges of 616-752 and 0.08-0.20 μg/L, respectively. The simplicity, high extraction efficiency, short sample preparation time, low cost, and safety demonstrated the efficiency of this method relative to other approaches.

Rapid and sensitive analysis of polychlorinated biphenyls and acrylamide in food samples using ionic liquid-based in situ dispersive liquid-liquid microextraction coupled to headspace gas chromatography

A simple and rapid ionic liquid (IL)-based in situ dispersive liquid-liquid microextraction (DLLME) method was developed and coupled to headspace gas chromatography (HS-GC) employing electron capture (ECD) and mass spectrometry (MS) detection for the analysis of polychlorinated biphenyls (PCBs) and acrylamide at trace levels from milk and coffee samples. The chemical structures of the halide-based ILs were tailored by introducing various functional groups to the cations to evaluate the effect of different structural features on the extraction efficiency of the target analytes. Extraction parameters including the molar ratio of IL to metathesis reagent and IL mass were optimized. The effects of HS oven temperature and the HS sample vial volume on the analyte response were also evaluated. The optimized in situ DLLME method exhibited good analytical precision, good linearity, and provided detection limits down to the low ppt level for PCBs and the low ppb level for acrylamide in aqueous samples. The matrix-compatibility of the developed method was also established by quantifying acrylamide in brewed coffee samples. This method is much simpler and faster compared to previously reported GC–MS methods using solid-phase microextraction (SPME) for the extraction/preconcentration of PCBs and acrylamide from complex food samples.

Ion-association dispersive liquid–liquid microextraction of ultra-trace amount of gold in water samples using Aliquat 336 prior to inductively coupled plasma atomic emission spectrometry determination

Gold is a rare and noble metal with atomic number of 79. Several techniques including both spectrometric and electrochemical methods are widely used to determine gold level in real samples. As a result of low concentration of gold in environmental samples, sample preparations such as extraction, clean-up, and pre-concentration before instrumental analysis are mandatory. Thus, a pre-treatment method (dispersive liquid–liquid microextraction (DLLME)) for gold pre-concentration and inductively coupled plasma optical emission spectrometry (ICP-OES) determination is proposed. An extraction method employing DLLME and ICP-OES has been developed for rapid separation, pre-concentration, and determination of ultra-trace amount of Au (III). The extraction of the analyte was performed in the presence of a quaternary ammonium cation, N-methyl-N,N,N-trioctylammonium chloride, (Aliquat 336) as an extractant based on ion-association extraction system. 1-Octanol and acetonitrile were used as extraction and disperser solvents, respectively. The variables affecting the extraction conditions were optimized. A calibration curve in the range of 0.3–100 ng mL−1, the detection limit of 0.09 ng mL−1, an enrichment factor of 150, and an extraction recovery of 74 % were obtained. The precision (RSD %) of the method was 6 % for five replicates and recoveries of 10 ng mL−1 Au(III). The combined DLLME method with ICP-OES can readily determine Au(III) at trace (μg L−1) level using only 10 mL of sample solution (tap, lake, and mining water) without interference by the matrices. This methodology is simple, fast, and low cost which can be used in routine analytical laboratories.

Rapid determination of some beta-blockers in complicated matrices by tandem dispersive liquid-liquid microextraction followed by high performance liquid chromatography.

In this research work, an efficient tandem dispersive liquid-liquid microextraction (TDLLME) procedure coupled with high performance liquid chromatography-ultraviolet detection (HPLC-UV) was successfully applied for thedetermination of beta-blockers in human plasma and pharmaceutical wastewater samples. High clean-up and preconcentration factor are easily and rapidly feasible via this novel, cheap, and safe microextraction method, leading to high quality experimental data. It consists of two sequential dispersive liquid-liquid microextraction methods, accomplished via air/ultrasonic agitation and air agitation, respectively. In order to enrich the optimal values for the mentioned procedures, the Box-Behnken design (BBD) combined with the desirability function (DF) was used. The optimum values were found to be 11.0% (w/v) of the salt amount, an initial pH value of 12.0, 103μL of organic extractant phase, and 45μL of aqueous extractant phase with pH value of 2.0, resulted in reasonable recovery percentages with a logical desirability. Under optimal experimental conditions, good linear ranges (3-2000ngmL-1 for metoprolol and 2.5-2500ngmL-1 for propranolol with the correlation of determinations (R 2s) higher than 0.99) and low limits of detection (0.8 and 1.0ngmL-1 for propranolol and metoprolol, respectively) were obtainable. Also, TDLLME-HPLC-UV provided good proper repeatabilities (relative standard deviations (RSDs) below 5.7%, n = 3) and high enrichment factors (EFs) of 75-100. Graphical abstract TDLLME of beta-blockers from complicated matrices.

Development of a dispersive liquid-liquid microextraction method using a lighter-than-water ionic liquid for the analysis of polycyclic aromatic hydrocarbons in water.

A dispersive liquid-liquid microextraction method using a lighter-than-water phosphonium-based ionic liquid for the extraction of 16 polycyclic aromatic hydrocarbons from water samples has been developed. The extracted compounds were analyzed by liquid chromatography coupled to fluorescence/diode array detectors. The effects of several experimental parameters on the extraction efficiency, such as type and volume of ionic liquid and disperser solvent, type and concentration of salt in the aqueous phase and extraction time, were investigated and optimized. Three phosphonium-based ionic liquids were assayed, obtaining larger extraction efficiencies when trihexyl-(tetradecyl)phosphonium bromide was used. The optimized methodology requires a few microliters of a lighter-than-water phosphonium-based ionic liquid, which allows an easy separation of the extraction solvent phase. The obtained limits of detection were between 0.02 and 0.56 μg/L, enrichment factors between 109 and 228, recoveries between 60 and 108%, trueness between 0.4 and 9.9% and reproducibility values between 3 and 12% were obtained. These figures of merit combined with the simplicity, rapidity and low cost of the analytical methodology indicate that this is a viable and convenient alternative to the methods reported in the literature. The developed method was used to analyze polycyclic aromatic hydrocarbons in river water samples.

Vortex-assisted ionic liquid-based dispersive liquid–liquid microextraction for assessment of chromium species in artificial saliva extract of different chewing tobacco products

A novel dispersive liquid-liquid microextraction (ILDLLμE) method using an extracting solvent (ionic liquid) and dispersant (Triton X-114) was developed for the separation and preconcentration of hexavalent chromium (Cr6+) in artificial saliva extract (ASE) of chewing tobacco products, gutkha, and mainpuri (n=23). In the proposed method, the extraction of Cr6+ was accomplished by using ammonium pyrrolidinedithiocarbamate (APDC) as complexing agent and 1-butyl-3-methylimidazolium hexafluorophosphate [C4MIM] [PF6] as extracting solvent. The tiny droplet of metal chelate was then dispersed into TX-114 emulsion, using vortex mixer. Various parameters such as concentration of APDC, pH of the solution, volume of [C4MIM] [PF6], and TX-114 as well as extraction time were studied. Under the most favorable conditions, the limit of detection was found to be 0.068μg/L with the relative standard deviation <5%. The enrichment factor of developed method was found as 62.5, and method has been effectively applied for the analysis of Cr species in artificial saliva extract of gutkha and mainpuri products. The Cr6+ was quantitatively recovered (<97%) under optimal conditions, while the recovery of trivalent specie (Cr3+), at the same experimental conditions, was observed to be <5%. The Cr3+ was determined by the difference of total Cr and Cr6+ in artificial saliva extract of selected STP. Health risks associated with the intake of total Cr in gutkha and mainpuri were assessed in terms of estimated daily intake, such as carcinogenic and noncarcinogenic risks. Estimated daily intake of Cr via chewing 10g/day of gutkha and mainpuri was found to be below the maximum tolerable daily intake, whereas the calculated risk of cancer for Cr was observed in the acceptable range of 10E-6-10E-4, except some brands of gutkha. Graphical Abstract ᅟ.

Dispersive liquid-liquid microextraction based on solidification of floating organic drop for preconcentration and determination of trace amounts of copper by flame atomic absorption spectrometry.

A novel, simple, rapid, sensitive, inexpensive and environmentally friendly dispersive liquid-liquid microextraction method based on the solidification of a floating organic drop (DLLME-SFO) was developed for the determination of copper by flame atomic absorption spectrometry (FAAS). N-o-Vanillidine-2-amino-p-cresol was used as a chelating ligand and 1-undecanol was selected as an extraction solvent. The main parameters affecting the performance of DLLME-SFO, such as sample pH, volume of extraction solvent, extraction time, concentration of the chelating ligand, salt effect, centrifugation time and sample volume were investigated and optimized. The effect of interfering ions on the recovery of copper was also examined. Under the optimum conditions, the detection limit (3σ) was 0.93μgL-1 for Cu using a sample volume of 20mL, yielding a preconcentration factor of 20. The proposed method was successfully applied to the determination of Cu in tap, river and seawater, rice flour and black tea samples as well as certified reference materials.

A novel application of carbon dots for colorimetric determination of fenitrothion insecticide based on the microextraction method

In this work, the intrinsic colorimetric property of carbon dots (CDs) was utilized for the determination of fenitrothion by applying dispersive liquid-liquid microextraction (DLLME) method. Label free CDs are extracted into carbon tetrachloride via assistance of trioctylmethylammonium chloride (Aliquat 336), which also acts as a disperser agent in this technique. The enriched CDs show an absorption signal at 365nm, which increases in the presence of fenitrothion. The absorbance increase of CDs in organic phase was used as an analytical signal for the determination of fenitrothion. The synthesized CDs were characterized by UV–visible, fluorescence, Fourier transform infrared (FT-IR) and transmission electron microscopic (TEM). Under the optimized conditions, beer's law was obeyed in the range of 1.0–250.0ngmL−1 of fenitrothion with the limit of detection for fenitrothion was 0.2ngmL−1. The relative standard deviation for eight replicate measurements of fenitrothion at concentrations of 25 and 100ngmL−1 were calculated to be 1.5 and 3.7%, respectively. The proposed method was successfully applied in the determination of fenitrothion in water samples with satisfactory results.

Fluorescent derivatization combined with aqueous solvent-based dispersive liquid-liquid microextraction for determination of butyrobetaine, l-carnitine and acetyl-l-carnitine in human plasma

A novel aqueous solvent-based dispersive liquid-liquid microextraction (AS-DLLME) method was combined with narrow-bore liquid chromatography and fluorescence detection for the determination of hydrophilic compounds. A remover (non-polar solvent) and extractant (aqueous solution) were introduced into the derivatization system (acetonitrile) to obtain a water-in-oil emulsion state that increased the mass transfer of analytes. As a proof of concept, three quaternary ammonium substances, including butyrobetaine, l-carnitine and acetyl-l-carnitine, were also used as analytes and determined in pharmaceuticals, personal care products, food and human plasma. The analytes were derivatized with 4-bromomethylbiphenyl for fluorescence detection and improved retention in the column. The linear response was 10–2000nM for l-carnitine and acetyl-l-carnitine with a good determination coefficient (r2>0.998) in the standard solution. The detection limit for l-carnitine and acetyl-l-carnitine was 4.5 fmol. The method was also successfully applied to a 1μL sample of human plasma. In the linearity calculations for determining butyrobetaine, l-carnitine and acetyl-l-carnitine in human plasma, the determination coefficients ranged from 0.996 to 0.999. Linear regression exhibited good reproducibility and a relative standard deviation better than 7.50% for the slope and 9.06% for the intercept. To characterize highly hydrophilic compounds in various samples, the proposed method provides good sensitivity for a small sample volume with a low consumption of toxic solvents.

Simple field-based automated dispersive liquid-liquid microextraction of trace level phthalate esters in natural waters with gas chromatography and mass spectrometric analysis.

A small, simple, and field-based automated dispersive liquid-liquid microextraction method followed by gas chromatography mass spectrometric analysis was developed for trace level phthalate esters analysis in natural waters. With a single syringe pump that is coupled with a multiposition valve, the whole extraction procedure including cleaning, sampling, mixing of extractant and disperser solvents, extraction, phase separation, and analytes collection was carried out in a totally automated way with a sample throughput of 21 h(-1) . Key factors, such as type and ratio of the extractant and disperser solvent, aspiration flow rate, extraction time, and matrix effect, were thoroughly investigated. Under the optimum conditions, linearity was found in the range from 0.03 to 60 μg/L. Limits of detection ranged from 0.0015 to 0.003 μg/L. Enrichment factors were in a range of 106-141. Reproducibility and recoveries were assessed by testing a series of three natural water samples that were spiked with different concentration levels. Finally, the proposed method was successfully applied in analysis of real surface waters. The developed system is inexpensive, light (2.6 kg), simple to use, applicable in the field, with high sample throughput, and sensitive enough for trace level phthalate esters analysis in natural waters.

Faster dispersive liquid-liquid microextraction methods using magnetic ionic liquids as solvents

Three hydrophobic magnetic ionic liquids (MILs) containing the tetrachloromanganate(II) (MnCl42−) anion, namely, aliquat tetrachloromanganate(II) ([Aliquat+]2[MnCl42−]), methyltrioctylammonium [MnCl42−] ([N1,8,8,8+]2[MnCl42−]), and trihexyltetradecylphosphonium [MnCl42−] ([P6,6,6,14+]2[MnCl42−]) were employed as extraction solvents in DLLME coupled to high-performance liquid chromatography (HPLC) employing UV detection. The MILs were developed with the features of magnetic susceptibility to permit rapid retrieval of the extraction solvent, hydrophobicity to allow for phase separation from water, and mobile phase compatibility with reversed phase HPLC. Additionally, the MILs were customized to minimize hydrolysis of the anionic component in aqueous media as well as reduce absorbance when subjected to HPLC. The three MILs were applied for the extraction of pharmaceutical drugs, phenolics, insecticides, and polycyclic aromatic hydrocarbons. The disperser solvent type, disperser solvent volume, mass of MIL, extraction time, the pH of the sample solution, and salt concentration were studied in order to achieve optimal extraction efficiency for each MIL. The [P6,6,6,14+]2[MnCl42−] MIL exhibited the best extraction efficiencies for most of the target analytes compared to the other MILs. Good linearity was obtained using this MIL with correlation coefficients (R) varying from 0.997 to 0.999. The limits of detection (LODs) of all analytes ranged from 0.25 to 1.00μgL−1. The relative recovery was studied in lake water and river water. The relative recovery in lake water varied from 53.8% to 114.7% at a spiked concentration of 20μgL−1 (5μgL−1 for phenanthrene) and from 52.1% to 106.7% at 150μgL−1 (37.5μgL−1 for phenanthrene). In river water, the relative recovery varied from 44.6% to 110.7% at a spiked concentration of 20μgL−1 (5μgL−1 for phenanthrene) and 42.9% to 83.6% at 150μgL−1 (37.5μgL−1 for phenanthrene).

Development of a dispersive liquid-liquid microextraction method with a new sequence of steps and its comparison with a conventional method.

In this paper, a dispersive liquid-liquid microextraction method with a new sequence of steps from the view of salt addition has been developed for the extraction and preconcentration of some organophosphorous pesticides from aqueous samples before analysis by gas chromatography with flame ionization detection. In this method, an appropriate mixture of extraction and disperser solvents is rapidly injected by a syringe into the aqueous sample. Then, sodium chloride is added into the solution to increase its ionic strength. The obtained results by the proposed method are compared with those of the conventional dispersive liquid-liquid microextraction in which the salt is added into the aqueous phase before dispersion of the extraction solvent. Some effective parameters on the method efficiency including type and volume of extraction and disperser solvents, type and percent of salt, etc. are investigated. Under the optimal conditions, limits of detection and quantification of the proposed method compared to conventional one were improved by a factor between 1.4-2.2 and 1.3-2.3, respectively. Extraction recoveries and enrichment factors of the proposed method with respect to conventional one enhanced from 43-60 to 72-99% and 1433-2000 to 2404-3285, respectively.