In-syringe Dispersive Liquid-liquid Microextraction Research Articles

Combination of microwave-assisted solvent extraction and effervescence-assisted deep eutectic solvent-based in-syringe dispersive liquid-liquid microextraction and its application in the extraction of triazine pesticides from apple samples.

In the current study, a combination of microwave-assisted solvent extraction combined with effervescence-assisted deep eutectic solvent-based in-syringe dispersive liquid-liquid microextraction has been developed as a new sample pretreatment method. The offered method was used for the extraction of five triazine pesticides (atrazine, propazine, cyanazine, ametryn, and simazine) from apple samples before their determination by gas chromatography-flame ionization detection. For this purpose, briefly, the apple sample was contacted with a suitable acidified extraction solvent and the mixture was exposed to microwave irradiations. Then, the supernatant was taken and mixed with a few microliters of a low-density deep eutectic solvent. The supernatant phase containing the extracted analytes was injected into a sodium bicarbonate solution filled into a syringe. Consequently, the effervescence reaction occurs and the analytes were extracted into the fine droplets of extractant dispersed throughout the solution. Afterward, an aliquot of this phase was analyzed by the chromatographic system. Satisfactory outcomes include high enrichment factors (228-261) and extraction recoveries (67-87%), good repeatability (relative standard deviations equal to or less than 3.2% and 5.3% for intra- and inter-day precisions), and low limits of detection (0.4-0.7 ng/g) and quantification (1.4-2.3 ng/g) were acquired under the best experimental situations.

Flow-based determination of lead exploiting in-syringe dispersive liquid-liquid micro-extraction in xylene and integrated spectrophotometric detection

A lab-in-syringe flow system exploiting dispersive liquid-liquid micro-extraction in a solvent lighter than water is proposed for the spectrophotometric determination of lead in industrial residual waters. The steps inherent to both liquid-liquid extraction and monitoring of the formed compound are in-syringe carried out. The classical carbon tetrachloride is not used as the extracting solvent, as it does not present the friendly characteristics inherent to the Green Analytical Chemistry. Aiming at a cleaner alternative for this determination, xylene is selected. Enrichment factor, linear dynamic range, detection limit, sample throughput and residue volume inherent to the proposed procedure were estimated as 36, 50.0–250 μg L−1, 9.0 μg L−1, 13 h−1, and 2.0 mL, respectively.

Flow-Based Determination of Lead Exploiting In-Syringe Dispersive Liquid-Liquid Micro-Extraction in Xylene and Integrated Spectrophotometric Detection

Flow-Based Determination of Lead Exploiting In-Syringe Dispersive Liquid-Liquid Micro-Extraction in Xylene and Integrated Spectrophotometric Detection

Determination of long-chain fatty acids in anaerobic digester supernatant and olive mill wastewater exploiting an in-syringe dispersive liquid-liquid microextraction and derivatization-free GC-MS method.

Long-chain fatty acids (LCFA) are commonly found in lipid-rich wastewaters and are a key factor to monitor the anaerobic digesters. A new simple, fast, precise, and suitable method for routine analysis of LCFA is proposed. The system involves in-syringe-magnetic stirring-assisted dispersive liquid-liquid microextraction (DLLME) prior to gas chromatography-mass spectrometry (GC-MS) without a derivatization process. Calibration curves were prepared in an ethanol solution (R2 ≥ 0.996), which was also useful as disperser solvent. Hexane was chosen as the extraction solvent. Several parameters (pH, ionic strength, extraction solvent volume, stirring time) were optimized in multivariate and univariate studies. Limits of detection (LODs) were found in the range 0.01-0.05mgL-1 and good precision inter-day (RSDs≤7.9%) and intra-day (RSDs≤4.4%) were obtained. The method was applied to quantify LCFA in supernatants of anaerobic digesters and olive mill wastewaters (OMW). Palmitic, stearic, and oleic acids were the most abundant fatty acid in the analyzed samples and the relative recoveries for all of them were between 81 and 113%.

Application of natural deep eutectic solvents-based in-syringe dispersive liquid-liquid microextraction for the extraction of five acaricides in egg samples

ABSTRACT An efficient sample preparation method has been developed for the simultaneous analysis of amitraz, fipronil, fipronil sulfone, carbaryl and cypermethrin in egg based on in-syringe dispersive liquid-liquid microextraction. In this process, the sample is transferred into a glass test tube and suitable volumes of zinc acetate solution and choline chloride-ascorbic acid deep eutectic solvent are added to the tube and the mixture is sonicated. After centrifugation, the separated phase is mixed with deionised water to decrease its viscosity. Then, it is mixed with a ternary deep eutectic solvent (choline chloride-acetic acid-n-octanol) and dispersed into deionised water filled into barrel of a syringe.The method has low limits of detection (0.70–2.4 ng g−1) and quantification (2.3–8.0 ng g–1), good linearity (r2 ≥ 0.9968), and satisfactory repeatability (relative standard deviation ≤ 11% for intra–(n = 6) and inter-day (n = 5) precisions). Finally, the proposed method was applied on different egg samples and cypermethrin and fipronil sulfone were found in three of them.

In-syringe dispersive liquid-liquid microextraction vs. solid phase extraction: A comparative analysis for the liquid chromatographic determination of three neonicotinoids in cotyledons

A novel extraction strategy for the determination of imidacloprid, thiamethoxam and clothianidin in soy cotyledons by liquid chromatography was developed based on the implementation of an in-syringe-dispersive liquid-liquid microextraction system, optimized through successive experimental designs. First, a fractional factorial design was built to screen the influence of five experimental factors: a) aqueous solution (water or ethylenediaminetetraacetic acid 0.20 mol L–1); b) type of solvent (methanol or acetonitrile); c) use of salt (yes or no) for the adjustment of the ionic strength; d) homogenization method (vortex or sonication); and e) extractant solvent (toluene or ethyl acetate). Afterwards, in order to build a response surface model, a central composite design was implemented considering the influencing factors. For the in-syringe-dispersive liquid-liquid microextraction system, optimal conditions resulted in 1140 µL of acetonitrile, 583 µL of ethyl acetate and three successive extractions. Finally, due to fact that the system involves an evaporation step, a simplex-lattice mixture design was built. The optimum composition of the resuspension solution was methanol:water (60:40 v/v). The developed method was compared with a previously reported solid phase extraction methodology taken as reference method. Higher recovery percentages were achieved with the novel procedure, i.e. in the range of 69.5 to 74.2%, for the three considered analytes.

Pressure variation in-syringe dispersive liquid-liquid microextraction associated with digital image colorimetry: Determination of cobalt in food samples

In the present work, preconcentration by pressure variation in-syringe dispersive liquid-liquid microextraction (PV-IS-DLLME) was used for the determination of cobalt by digital image colorimetry. The detection system, built in the laboratory, involved a portable multifunction microscope used for image acquisition. The extraction solvent was trichloroethylene, while 2,2′-(thiazolylazo)-p-cresol (TAC) was used as a complexing agent. The pH, volume of extraction solvent, sample volume, and time of extraction were evaluated using a fractional factorial design 24-1. All factors were significant, and their optimum values were established with a central composite design. The limits of detection and quantification presented by the method were 0.08 and 0.23 mg kg−1, respectively, and the enrichment factor was 65. The procedure was applied to the analysis of real food samples (green banana flour, eggplant, Bahian seasoning, and Tribulus terrestris) and a certified reference material (NIST 1573a, tomato leaves). The PV-IS-DLLME technique presented itself as an efficient, simple, fast, and low-cost alternative for the preconcentration of substances at trace levels.

In-syringe dispersive liquid-liquid microextraction using deep eutectic solvent as disperser: Determination of chromium (VI) in beverages

A novel approach for dispersive liquid-liquid microextraction based on the use of deep eutectic solvent as a disperser was presented for the first time. The procedure was automated based on an in-syringe flow system coupled with UV–Vis detection and demonstrated by the determination of chromium (VI) in beverages. This analytical task was used as a proof-of-concept example. The automated extraction procedure involved the aspiration of aqueous sample into a syringe pump with homogeneous mixture of extraction solvent (1-oсtanol) and deep eutectic solvent (tetrabutylammonium bromide – formic acid) containing color-forming reagent (1,5-diphenylcarbazide). This led to decomposition of deep eutectic solvent in aqueous phase resulting in dispersion of extraction solvent, oxidation of 1,5-diphenylcarbazide to 1,5- diphenylcarbazone in the presence of chromium (VI), and formation of colored chromium (III) complex with 1,5-diphenylcarbazone and its fast extraction. In this case composition of deep eutectic solvent played a key role for analyte extraction. Tetrabutylammonium bromide promoted mass transfer between aqueous phase and the extraction solvent droplets as a salting out agent, bromide ion acted as an ion-pare agent for analyte complex extraction, formic acid provided required pH value for analyte complex formation. Under the optimal conditions the limit of detection, calculated from a blank test based on 3s, was 0.2 μg L−1. The automated dispersive liquid-liquid microextraction using deep eutectic solvent as disperser can be considered as an available, efficient, rapid and environmentally friendly sample pretreatment approach.

Automated continuous-flow in-syringe dispersive liquid-liquid microextraction of mono-nitrophenols from large sample volumes using a novel approach to multivariate spectral analysis

Continuous magnetic stirring-assisted dispersive liquid-liquid extraction followed by dispersive backextraction as a novel pre-treatment technique for adaptable and milliliter volumes of environmental samples has been developed. The procedure was automated using the technique “Lab-In-Syringe”. The void of the automated syringe pump was used as size-adaptable extraction chamber. By a flow channel in the syringe piston, continuous flow through the syringe void was enabled. 1-Octanol was used as an extractant and dispersed by the action of a magnetic stirring bar, which was placed inside the syringe and driven by an external rotating magnetic field. Extract washing and dispersive backextraction in an alkaline aqueous acceptor phase were carried out after the preceding extraction from the acidified water sample. Analyte determination was achieved using multivariate spectrum analysis. The method was applied to determine priority pollutants, mono-nitrophenols, in surface water and enabled to reach limits of detection for o-, m-, p-nitrophenol (λ = 418, 390, 400 nm, respectively) of 0.14, 0.26, and 0.02 μmol L−1 (19.5, 36.2, and 2.8 μg L−1), respectively. Under optimized conditions, relative standard deviations were generally less than 5% and enrichment factors of o-, m-, p-nitrophenol 19, 25, and 21, respectively, were achieved using sample volumes of up to 24 mL. Average recoveries of o-, m-, p-nitrophenol from spiked surface water were 94, 82, and 92%, respectively. The concentration of humic acid was found 6-times reduced with respect to the analyte. In addition, adding spectral background modeling allowed nitrophenol determination with precision adequate for routine analysis.

A novel strategy based on in-syringe dispersive liquid-liquid microextraction for the determination of nickel in chocolate samples

In this work, a novel approach was developed to perform dispersive liquid–liquid microextraction using a rapid pressure variation to disperse the extraction solvent in an aqueous medium. A glass syringe was used to produce an environment subject to a rapid pressure difference. The element used as a model was nickel and the approach was called pressure variation in-syringe dispersive liquid-liquid microextraction (PV-IS-DLLME). The extraction solvent used was 1-butyl-3-methylimidazolium hexafluorophosphate, and ammonium pyrrolidine dithiocarbamate was the complexing reagent. The variables pH, solvent volume, amount of complexing agent, extraction time and syringe volume were studied by a factorial 25–1 fractional design. All variables were significant. However, the two least significant, amount of complexing agent (50.0 μL) and syringe volume (20.0 mL) were fixed at their optimum levels, according to the generated Pareto chart. A Doehlert matrix was studied for the variables volume of solvent, pH and extraction time to obtain optimal levels of these factors, and the contour plots showed the following critical values: 120.0 μL, 2.0 and 60.0 s respectively. The developed method presented limits of detection and quantification of 0.1 and 0.3 mg kg−1, an enrichment factor of 17 and a precision of 4.8% (100.0 μg L−1). The developed method was applied to the analysis of samples of powdered chocolate and certified reference material.

Online coupling of fully automatic in-syringe dispersive liquid-liquid microextraction with oxidative back-extraction to inductively coupled plasma spectrometry for sample clean-up in elemental analysis: A proof of concept

A proof of concept of a novel automatic sample cleanup approach for metal assays in troublesome matrixes as a front-end sample pre-treatment to inductively coupled plasma optical emission spectroscopy – ICP-OES – is herein presented. Target metals, namely, copper, lead, and cadmium were complexed in-system quantitatively using ammonium pyrrolidine dithiocarbamate (APDC) and transferred into a minute volume of toluene as extractant employing lab-in-syringe magnetic stirring-assisted dispersive liquid-liquid microextraction (LIS-MSA-DLLME). After discharge of the sample, the analytes were back-extracted into nitric acid and injected on-line into ICP-OES. To promote and expedite this process in-syringe, advantage was taken from oxidative decomposition of the chelate by potassium iodate, reported in this article for the first time.Experimental conditions for LIS-MSA-DLLME were optimized by Box-Benkhen multivariate analysis using the geometric mean of analyte recoveries as the desirability function. Times of extraction and back-extraction of 300s and 100s, respectively, pH 5.5 at 30mmol/L acetate, 300µL of extraction solvent, and 600µmol/L of APDC were finally applied. Online interfacing to ICP-OES for back-extract analysis yielded average repeatabilities for Cd, Cu, and Pb of 2.9%, 3.5%, and 3.5% with limits of detections (3s) of 1.9, 1.4, and 5.6ng/mL, respectively. Oxidative back-extraction was proven reliable for the determination of metal species in coastal seawater, surrogate digestive fluids and soil leachates with recovery values for Cd, Cu, and Pb ranging from 90% to 118%, 68% to 104%, and 86% to 112%, respectively.

In-Syringe Dispersive Liquid-Liquid Microextraction Coupled with High- Performance Liquid Chromatography for Trace Analysis of Naphthalene Sulfonates in Seawater

In-Syringe Dispersive Liquid-Liquid Microextraction Coupled with High- Performance Liquid Chromatography for Trace Analysis of Naphthalene Sulfonates in Seawater

In-syringe dispersive liquid-liquid microextraction based on the solidification of ionic liquids for the determination of benzoylurea insecticides in water and tea beverage samples

A novel in-syringe dispersive liquid-liquid microextraction based on the solidification of ionic liquids (in-syringe SIL-DLLME) was coupled with high-performance liquid chromatography-ultraviolet detector (HPLC-UVD) to detect five benzoylurea insecticides (BUs) in water and tea beverage samples. In this method, the hydrophobic ionic liquid [N8881][PF6] was formed in situ by the metathesis reaction between [N8881]Cl and the anion-exchange reagent KPF6 to extract the target analytes. The whole extraction procedure was performed in a syringe. The solidified extractant could be separated from the aqueous phase by exposing the emulsified extraction solution to an ice bath and then easily collected by squeezing out the aqueous phase through the prepared NWPP-based needle. Various parameters affecting the extraction efficiency, such as the amount of [N8881]Cl, the molar ratio of [N8881]Cl to KPF6, salt addition, cooling time, solution temperature, sample pH and sample volume, were evaluated. Under the optimized conditions, the proposed method was validated with satisfactory results: good linearities with coefficients of determination greater than 0.99 were obtained in the range of 2–500µgL−1; the limits of detection varied between 0.29 and 0.59µgL−1; the recoveries of the five benzoylurea insecticides ranged from 85.93% to 90.52%; and the intra-day (n=3) and inter-day (n=3) relative standard deviations were less than 5.36%. Finally, the proposed method was successfully used for the determination of BUs in real water and tea beverage samples.

Fully-automated in-syringe dispersive liquid-liquid microextraction for the determination of caffeine in coffee beverages

A novel fully-automated magnetic stirring-assisted lab-in-syringe analytical procedure has been developed for the fast and efficient dispersive liquid-liquid microextraction (DLLME) of caffeine in coffee beverages. The procedure is based on the microextraction of caffeine with a minute amount of dichloromethane, isolating caffeine from the sample matrix with no further sample pretreatment. Selection of the relevant extraction parameters such as the dispersive solvent, proportion of aqueous/organic phase, pH and flow rates have been carefully evaluated.Caffeine quantification was linear from 2 to 75mgL−1, with detection and quantification limits of 0.46mgL−1 and 1.54mgL−1, respectively. A coefficient of variation (n=8; 5mgL−1) of a 2.1% and a sampling rate of 16h−1, were obtained. The procedure was satisfactorily applied to the determination of caffeine in brewed, instant and decaf coffee samples, being the results for the sample analysis validated using high-performance liquid chromatography.

Automatic in-syringe dispersive liquid-liquid microextraction of ⁹⁹Tc from biological samples and hospital residues prior to liquid scintillation counting.

A new approach exploiting in-syringe dispersive liquid-liquid microextraction (DLLME) for (99)Tc extraction and preconcentration from biological samples, i.e., urine and saliva, and liquid residues from treated patients is presented. (99)Tc is a beta emitter with a long half-life (2.111 × 10(5) years) and mobility in the different environmental compartments. One of the sources of this radionuclide is through the use of its father (99m)Tc in medical diagnosis. For the first time a critical comparison between extractants and disperser solvents for (99)Tc DLLME is presented, e.g., tributyl phosphate (TBP), trioctylmethylammonium chloride (Aliquat®336), triisooctylamine (TiOA), as extractants in apolar solvents such as xylene and dodecane, and disperser solvents such as acetone, acetonitrile, ethanol, methanol, 1-propanol, and 2-propanol. The system was optimized by experimental design, and 22.5% of Aliquat®336 in acetone was selected as extractant and disperser, respectively. Off-line detection was performed using a liquid scintillation counter. The present method has a (99)Tc minimum detectable activity (MDA) of 0.075 Bq with a high extraction/preconcentration frequency (8 h(-1)). Urine, saliva, and hospital residues were satisfactorily analyzed with recoveries of 82-119%. Thus, the proposed system is an automatic powerful tool to monitor the entry of (99)Tc into the environment. Graphical Abstract (99m)Tc is widely used in Nuclear Medicine for diagnosis. Its daugther (99)Tc is automatically monitored in biological samples from treated patients by in-syringe dispersive liquid-liquid microextraction.

Application of In-Syringe Dispersive Liquid-Liquid Microextraction Coupled to GC/FID for Determination of Trace Contamination of Phthalate Esters in Water Samples.

In this work, a simple and easy to handle one-step in-syringe setup for the dispersive liquid-liquid microextraction method has been developed for preconcentration of trace quantities of four kinds of phthalate esters (PEs) in water samples as a prior step to its determination by gas chromatography/flame ionization detector. The environmental pollution at this method has been limited due to using a glass syringe as extraction unit and also a very small amount of n-hexane as a safe solvent. Some important parameters such as the type of extraction and disperser solvents, extraction and disperser solvents volume, sample volume and ionic strength were investigated and optimized. Validation experiments showed that the optimized method had precision (1.7-6.9%) and high recovery (94.32-104.7%), and the limits of detection were from 0.406 to 1.33 µg L(-1). At the end, the method was successfully applied for the determination of PEs in real water samples.

Comparison of single best artificial neural network and neural network ensemble in modeling of palladium microextraction

A simple, efficient, and fast method based on in-syringe dispersive liquid–liquid microextraction (IS-DLLME) for preconcentration of trace amounts of palladium from aqueous samples was developed. After complexation with 5-(4-dimethylaminobenzylidene)rhodanine, Pd was extracted into benzyl alcohol before its measurement with UV–Vis spectrophotometer, equipped with cubic millimeter cells. Thereafter, a comparative study between single best artificial neural network (SB-NN) and neural network ensemble (NNE) was performed to find the best mathematical model for palladium extraction process to simulate IS-DLLME. Two NNE models were built, one without pruning (NNE-WP) the ensemble members and another with pruning using genetic algorithm (NNE-GA). The predictive and generalization ability of SB-NN, NNE-WP, and NNE-GA was compared based on 20 runs. The average % error for SB-NN, NNE-WP, and NNE-GA models was 0.234, 0.146, and 0.115 and the correlation coefficient was 0.902, 0.948, and 0.973, respectively; indicating superiority of NNE approaches specially NNE-GA in capturing the non-linear behavior of the system.

Application of In-Syringe Dispersive Liquid-Liquid Microextraction and Narrow-Bore Tube Dispersive Liquid-Liquid Microextraction for the Determination of Trace Amounts of BTEX in Water Samples.

Two new simple and effective methods based on dispersive liquid-liquid microextraction (DLLME) procedure, termed "in-syringe DLLME (IS-DLLME)" and "narrow-bore tube DLLME (NB-DLLME)", were developed and applied for rapid and simultaneous separation and preconcentration of trace amounts of benzene, toluene, ethylbenzene and xylene isomers in water samples followed by gas chromatographic analysis. Different parameters influencing the extraction efficiency of both methods such as type and volume of the extraction solvent and the disperser solvent; pH, temperature and volume of sample solution and ionic strength of samples were investigated and optimized. Under optimal condition, the limits of detection ranged from 1.7 to 2.4 µg L(-1) for IS-DLLME and 1.5 to 2.2 µg L(-1) for NB-DLLME. Precision (as relative standard deviation) of the two techniques was between 2.1 and 4.6% for IS-DLLME and between 1.5 and 4.5% for NB-DLLME. The enrichment factors found to be between 20-29 and 31-73 for IS- and NB-DLLME, respectively. The applicability of the proposed methods was investigated by analyzing real water samples.

In‐syringe‐assisted dispersive liquid–liquid microextraction coupled to gas chromatography with mass spectrometry for the determination of six phthalates in water samples

A fully automated method for the determination of six phthalates in environmental water samples is described. It is based in the novel sample preparation concept of in-syringe dispersive liquid-liquid microextraction, coupled as a front end to GC-MS, enabling the integration of the extraction steps and sample injection in an instrumental setup that is easy to operate. Dispersion was achieved by aspiration of the organic (extractant and disperser) and the aqueous phase into the syringe very rapidly. The denser-than-water organic droplets released in the extraction step, were accumulated at the head of the syringe, where the sedimented fraction was transferred to a rotary micro-volume injection valve where finally was introduced by an air stream into the injector of the GC through a stainless-steel tubing used as interface. Factors affecting the microextraction efficiency were optimized using multivariate optimization. Figures of merit of the proposed method were evaluated under optimal conditions, achieving a detection limit in the range of 0.03-0.10 μg/L, while the RSD% value was below 5% (n = 5). A good linearity (0.9956 ≥ r(2) ≥ 0.9844) and a broad linear working range (0.5-120 μg/L) were obtained. The method exhibited enrichment factors and recoveries, ranging from 14.11-16.39 and 88-102%, respectively.

Comparison of two novel in-syringe dispersive liquid–liquid microextraction techniques for the determination of iodide in water samples using spectrophotometry

Two new, rapid methodologies have been developed and applied successfully for the determination of trace levels of iodide in real water samples. Both techniques are based on a combination of in-syringe dispersive liquid–liquid microextraction (IS-DLLME) and micro-volume UV–Vis spectrophotometry. In the first technique, iodide is oxidized with nitrous acid to the colorless anion of ICl2- at high concentration of hydrochloric acid. Rhodamine B is added and by means of one step IS-DLLME, the ion-pair formed was extracted into toluene and measured spectrophotometrically. Acetone is used as dispersive solvent. The second method is based on the IS-DLLME microextraction of iodide as iodide/1, 10-phenanthroline-iron(II) chelate cation ion-pair (colored) into nitrobenzene. Methanol was selected as dispersive solvent. Optimal conditions for iodide extraction were determined for both approaches. Methods are compared in terms of analytical parameters such as precision, accuracy, speed and limit of detection. Both methods were successfully applied to determining iodide in tap and river water samples.