Microextraction Preconcentration Research Articles

Extraction and Determination of Synthetic Food Dyes in an Aqueous Biphasic System Based on Tetrabutylammonium Bromide

An aqueous biphasic system (ABS) based on tetrabutylammonium bromide (TBABr) with ammonium sulfate as a salting-out agent was used to extract synthetic food dyes from aqueous solutions. Conditions for the preparation of the TBABr–H2O–(NH4)2SO4 ABS for microextraction preconcentration of Allura Red, Tartrazine, Azorubine, Sunset Yellow, and Fast Green were optimized: tetrabutylammonium bromide, 0.075 M and ammonium sulfate, 33 wt %. The recovery of all of the dyes was no lower than 97% at pH 2.3–9.5 for 1 min. Filtration through nonwoven polypropylene was used to facilitate phase separation and extract isolation. The concentrate was eluted with distilled water, and the dyes in the eluate were determined by spectrophotometry. The limits of detection were 0.02, 0.03, 0.03, 0.04, and 0.02 mg/L for Allura Red, Azorubine, Tartrazine, Sunset Yellow, and Fast Green, respectively. The procedure was applied to determine dyes in drinks, a mouthwash, an Easter kit for dyeing eggs, and the drug Ibuprofen.

Determination of Curcumin in Food with Homogenous Liquid-Phase Microextraction Preconcentration and Spectrophotometric Determination

Antioxidants play a role in the transformation of free radicals into more stable chemical structures. Work on phenolic antioxidants has accelerated in recent years. Curcumin is a natural phenolic with antioxidant properties. In this study, a salt-supported homogenous liquid-phase microextraction method was used for preconcentration and spectrophotometric determination of curcumin for the first time. The curcumin was transferred into the organic phase using cyclohexylamine as the extraction solvent at pH values between 2.0 and 7.0 and determined by spectrophotometry. The results showed that the performance of the method for curcumin was unaffected by pH. The pH of the sample solution, the mass of salt, and the volume of the solvent were optimized, and the influence of the matrix types was investigated. The limits of detection and quantification were 1.44 and 4.80 µg L−1 for curcumin. The developed method was employed for the analysis of food samples.

Microextraction Preconcentration of Chloroacetic Acids with the Flotation Separation of the Extract

Microextraction Preconcentration of Chloroacetic Acids with the Flotation Separation of the Extract

Palladium determination with a new dye PNBTAN: Structural, UV-VIS, and DFT study

A new method for the determination of palladium has been developed based on the dispersive liquid–liquid microextraction preconcentration with UV-VIS spectrometry detection. In the proposed approach, 1-[(5-(3-nitrobenzyl)-1,3-thiazol-2-yl)diazenyl]naphthalen-2-ol (PNBTAN) was used as a new chelating agent, and methyl isobutyl ketone and ethanol were selected as extraction and dispersive solvents. The limit of detection (LOD), based on the signal-to-noise (S/N) ratio of 3, was 0.093 µg mL–1. Linearity was observed over the range of 0.24-1.437 µg mL–1 with the correlation coefficient (R) of 0.9993. The developed method has been successfully tested and applied to the determination of trace amounts of palladium in real objects.Analytical properties of PNBTAN and its complexes with palladium were investigated by theoretical calculations and experimental spectrophotometric method. Electron localization function, Fukui function, and molecular electrostatic potential isosurfaces were analyzed as reactivity descriptors for the explanation of the PNBTAN chelation ability. DFT analysis of eleven possible structures of the Pd:PNBTAN (1:2) complex has established the preferred formation of six-membered -O-Pd-N = N- containing cycles. According to the TD-DFT calculations, the experimentally observed bands at 747 and 680 nm in the UV-VIS spectrum of the Pd:PNBTAN (1:2) complex were assigned to the HOMO→LUMO and HOMO→LUMO+1 electron transitions, respectively.

Dispersive Liquid–Liquid Microextraction of Organic Compounds: An Overview of Reviews

Dispersive liquid–liquid microextraction (DLLME) is one of the most promising methods of the microextraction preconcentration of organic compounds. This method is eco-friendly, simple, and universal; in comparison with conventional extraction, the consumption of the reagents and solvents, the time of extraction, and the cost of analysis in this method are reduced. For a short time from the moment of the appearance of DLLME in 2006, analysts developed numerous versions, differing by the method of dispersion, the nature of the extractant and by combinations with other methods of sample preparation and methods of the subsequent determination of the preconcentrated substances. The popularity of the method among the analysts is attested in a great number of reviews summarized in this publication.

Gas-Chromatographic Analysis of High-Purity Phosphorus Oxychloride with the Microextraction Preconcentration of Impurities

We developed a procedure for the gas-chromatographic determination of impurities in phosphorus oxychloride (POCl3) after the preliminary hydrolysis of the base and microextraction of impurities of organic and organochlorine substances with n-hexane. Impurities of chloroform, trichloroethylene, tetrachloroethylene, carbon tetrachloride, and benzene were identified. The degree of the microextraction of impurities is 0.17–0.76. The limits of detection for the impurities are at the level of 0.00009–0.007 mg/L, which is 4–300 times lower than those achieved previously.

Determination of chloroacetic acids using ion chromatography with liquid-phase microextraction preconcentration

In order to increase the sensitivity of the ion chromatographic determination of chlorinated acetic acids ( CAAs ) in water, an emulsion microextraction preconcentration was proposed. The emulsification of extractants was performed by the ultrasonic irradiation. Diethyl and methyl tert-butyl ethers were used as extractants. The comparison of extractants showed the advantages of methyl tert-butyl ether: stable aggregation into a separate phase after the dispersion, no loss of extractant at the analysis stages due to volatility. To reduce the detection limits and improve the chromatographic separation of analytes, the organic matrix of the extract was replaced by water. It was achieved by evaporating the extractant at room temperature and dissolving the dry residue in the eluent. Also, this operation eliminated the difficulties associated with the analysis of organic extracts using the ion chromatography with conductivity detector. The absence of loss of the analytes at this stage was experimentally proven. The dependences of the efficiency of microextraction preconcentration on the various process parameters (ultrasonic exposure time, centrifugation time, volume of extractant, salt additive concentration) were established. The detection limits reached were 1∙10 -3 ‒ 8∙10 -3 mg/l, which are 20-600 times lower than the maximum permissible values for CAAs. In addition, the advantages of this preconcentration technique over the published works were the simultaneous removal of interfering impurities, small volume of water samples (4.1 ml) and chromatograph injected volume (50 μl). The relative standard deviation did not exceed 25%. The proposed method was tested by analyzing the samples of tap water. Mono- and dichloroacetic acids were detected, their content did not exceed the MAC values. Keywords : chlorinated acetic acids, ion chromatography, microextraction preconcentration DOI: http://dx.doi.org/10.15826/analitika.2020.24.1.004 R.G. Sirotkin, E.V. Elipasheva, V.A. Krylov, R.E. Grubov, K.A. Lutoshkina National Research Lobachevsky State University of Nizhny Novgorod (UNN) Gagarin pr., 23, Nizhny Novgorod, 603950, Russian Federation

Automation of Microextraction Preconcentration Methods Based on Stepwise Injection Analysis

We present a review of microextraction methods of separation and preconcentration, automated using the principles of equilibrium flow methods of analysis. The concepts and possibilities of automated methods of single-drop microextraction, dispersive microextraction, and homogeneous liquid–liquid extraction are discussed. The analytical potential of these methods is confirmed by some examples of analysis of food products and biological fluids.

New Directions in Using Ionic Liquids in Analytical Chemistry. 1: Liquid–Liquid Extraction

The first part of the review presents general information and brief historical notes about ionic liquids (ILs) along with various versions of microextraction preconcentration using ILs: single-drop extraction, membrane extraction, dispersive liquid–liquid microextraction, in situ ionic liquid-based dispersive microextraction, etc. A review of papers on the extraction of metal ions and organic compounds in ILs for chemical analysis is presented. Aqueous biphasic systems based on ILs immiscible with water and salting-out agents are described; examples of such systems, their advantages, and factors affecting phase separation are considered.

Vortex assisted in situ ionic liquid dispersive liquid–liquid microextraction for preconcentration of uranyl ion in water samples before spectrophotometric detection

Vortex assisted in situ ionic liquid dispersive liquid–liquid microextraction method was developed for extraction of U(VI) from aqueous solutions using hydrophilic ionic liquid and ion-exchange reagent. Arsenazo III was used as a complexing agent in microextraction process. Under optimized conditions, the proposed method for uranyl ion exhibited good precision, 5.2% for 1 µg L−1 and 5.1% for 4 µg L−1, low limit of detection, 0.06 µg L−1 and high enrichment factor, 91. The accuracy studies were achieved by spiking of 1 and 5 µg L−1 U(VI) into water samples and the recovery was found in the range of 99–111%.

Improving the organic solvents purity for microextraction preconcentration of impurities

The purity of different industrially produced extractants, such as hexane, n-octane, carbon tetrachloride, and ethanol, was studied using gas chromatography-mass spectrometry and gas chromatography. It was shown that the most characteristic impurities in these extractants were volatile organochlorine compounds ( LHS ) and hard volatile esters of o-phthalic acid ( o -phthalates ). The impurity content of these substances in extractants could reach tens of mg/l. Based on the calculation of the distribution coefficients of impurities in the “liquid-vapor” system, the methods of Rayleigh distillation and rectification were proposed for removing the impurities from the extractants. Gas chromatographic mass spectrometric and gas chromatographic analysis of purified extractants showed that the effective removal of impurities of o-phthalic acid esters was possible using the Rayleigh distillation during the distillation of extractants at an evaporation rate of no more than 6·10 –4 ml·cm –2 ·s –1 . This allowed obtaining a volume of extractant enough to carry out 50-55 microextractions in 5 minutes. The effective removal of volatile LHS was achieved by a multi-stage distillation method - rectification. The concentration of impurities of the investigated substances in the purified extractants did not exceed 10 –3 –10 –5 mg/l. The liquid-phase microextraction preconcentration with the use of purified extractants decreased the detection limits of LHS and o-phthalates in the water to 2∙10 -7 -1∙10 -5 and 4·10 -6 ‒1·10 -5 mg/l, respectively. Keywords: microextraction preconcentration, rectification, Rayleigh distillation, detection limits, extractant, gas chromatography, gas chromatography mass spectrometry (Russian) DOI: http://dx.doi.org/10.15826/analitika.2019.23.1.008 V.A. Krylov 1 , P.V. Mosygin 1 , L.V. Smirnova 1 , S.A. Bulanova 1 , I.A. Zhituhina 1 , G.V. Pushkarev 2 1 N.I. Lobachevsky Nizhny Novgorod State University, Russian Federation, 603950, Nizhny Novgorod, Gagarin pr., 23 2 Joint –Stock Company «Scientific - Production Enterprise «Salyut», Russian Federation, 603950, Nizhny Novgorod, Larina Str., 7

Spectrophotometric Determination of the Total Iodine Content in Drinking and Mineral Waters Using the Microextraction Preconcentration

Optimal conditions for the microextraction concentration and spectrophotometric determination of iodine (I, V, VII) forms as ionic associates of triiodide anions with the cation of astrazone brilliant red 4G dye have been found. A new procedure for the spectrophotometric determination of the total iodine content in drinking and mineral waters with the detection limit of 8.9 μg/dm3 was developed and tested. This procedure is combined with microextraction concentration and meets the requirements of “green” chemistry.

Ionic Liquid Based Ultrasound-Assisted Emulsification Microextraction for Preconcentration of Phenol Using Central Composite Design

In this work, phenol reacted with 4-aminoantipyrine (4-AAP) reagent in presence of potassium hexacyanoferrate(III) and then was extracted using ultrasound-assisted emulsification microextraction via 1-hexyl-3-methyl imidazolium hexafluorophosphate as an environmentally friendly solvent. Effects of the main experimental variables were investigated and optimized by central composite design. Under the optimum conditions (pH 9.5, 100 mg/L 4-AAP, 100 μL of ionic liquid as extraction solvent, 0.2 g/L K3Fe(CN)6 and 0.2 M NH4Cl) the dynamic linear range, limit of detection and relative standard deviation were obtained as 0.2‒25 μg/L, 0.07 μg/L and 2.6%, respectively. Finally, the applicability of the proposed ultrasoundassisted emulsification microextraction was examined and very good results were obtained. The results confirmed the applicability of the proposed method as a versatile, low cost and sensitive preconcentration method for determination of very low concentrations of phenol in aqueous solutions.

Optimization of ultrasound-assisted magnetic retrieval-linked ionic liquid dispersive liquid–liquid microextraction for the determination of cadmium and lead in water samples by graphite furnace atomic absorption spectrometry

Abstract A simple and efficient method for the determination of Cd and Pb in water samples was developed by ultrasound-assisted magnetic retrieval-linked ionic liquid dispersive liquid–liquid microextraction (UA-MR-IL-DLLME) preconcentration and graphite furnace atomic absorption spectrometry (GFAAS) detection. Ionic liquid (IL) [Hmim] [PF6] was used as the extractant, ammonium pyrrolidine dithiocarbamate (APDC) as the complexing agent and Fe3O4 nanoparticles as the sorbent, while ultrasound was applied to assist the dispersion of the extractant and accelerate the mass transfer process. The effect of different factors on the extraction efficiency including pH, IL volume, APDC amount, ultrasound extraction time, ultrasound desorption time and Fe3O4 amount was studied by a fractional factorial design to screen for the most important factors. Then a central composite design was used to optimize the significant factors. Under the optimal conditions, the method has linear calibration curves over the range of 0.3–20 ng/mL for Cd and 0.5–40 ng/mL for Pb, with correlation coefficients (R) of 0.9990 and 0.9986 for Cd and Pb, respectively. The limits of detection were 0.1 ng/mL and 0.15 ng/mL with relative standard deviations of 3.4% and 2.8% for Cd and Pb, respectively. Finally, the method was successfully applied for the determination of Cd and Pb in the real water samples and satisfactory recoveries were achieved.

Gas chromatographic determination of benzothiophenes in high-purity sulfur

A procedure is developed for the determination of benzothiophene, dibenzothiophene, and 4,6-dimethyldibenzothiophene in high-purity sulfur, including liquid-phase microextraction preconcentration, identification by gas chromatography−mass spectrometry, and gas chromatographic determination with flame photometric detection. The rate of microextraction recovery was from 16 to 78%. The limits of detection were 8 × 10–5 wt % for benzophiophene and 2 × 10–5 wt % for dibenzothiophene and 4,6-dimethyldibenzothiophene.

Determination of o-phthalic acid esters in water by chromatography–mass spectrometry with emulsion dispersive liquid–liquid microextraction preconcentration

Using emulsion dispersive liquid–liquid microextraction preconcentration and injection of a large volume of an extract (10 μL), the limits of chromatographic–mass spectrometric detection of o-phthalic acid esters in water have been attained at the level 4 × 10–6–1 × 10–5 mg/L. The main source of the systemic error of the determination of impurities was found to be the release of o-phthalates from microparticles of chromatographic septum to the carrier gas. The extractant (n-octane) was purified by Rayleigh distillation. The independence of the concentration coefficient of the studied o-phthalates of concentration in the range (0.4–30) × 10–4 mg/L has been demonstrated. The relative expanded uncertainty of the determination of o-phthalates has been calculated and equals 12–39%.

Determination of ultra-trace palladium (II) in water, soil, and food samples by dispersive liquid‐liquid microextraction-atomic absorption spectrometry using 2-mercaptobenzimidazole as a complexing agent

A new, simple, and rapid method was developed for selective extraction and determination of trace levels of Pd(II) by dispersive liquid‐liquid microextraction (DLLME) preconcentration and flame atomic absorption spectrometry detection. In the developed method, 2-mercaptobenzimidazole (MBI) was used as a Pd(II) complexing agent. Chloroform and acetone were selected as the extraction and dispersive solvents, respectively. The effective DLLME parameters such as pH, kinds of extraction and dispersive solvents and their volumes, concentration of the complexing agent, and extraction time were studied and optimized. Under the optimum experimental conditions, the calibration graph was linear over the range of 15‐1100 μg L−1 with a detection limit (3σ) of 8 μg L−1 for palladium(II). The relative standard deviations (RSDs, n = 6) were lower than 4.8%. The enhancement factor was obtained to be 20.7. This environmentally‐friendly method was successfully applied to the determination of trace levels of palladium(II) in soil, food, and spiked waterfall and tap water samples. The accuracy the developed method was also evaluated by the analysis of the certified reference material GPP-10.

Ionic Liquid Based Dispersive Liquid–Liquid Microextraction for Preconcentration of Zearalenone and Its Determination in Beer and Cereal Samples by High-Performance Liquid Chromatography with Fluorescence Detection

A simple, fast, and efficient ionic liquid based dispersive liquid–liquid microextraction has been developed for the determination of trace amounts of zearalenone for the first time. Preconcentrated zearalenone was determined by high performance liquid chromatography with fluorescence detector. Two ionic liquids, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl) imide and 1-methyl-3-octylimidazolium bis(trifluoromethanesulfonyl) imide were used as extraction solvents. Several analytical parameters affecting the extraction efficiency such as sample pH, type, and volume of dispersive solvent, volume of ionic liquid, time of extraction, and centrifugation were optimized. The 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl) imide showed the better extraction efficiency. Thus, the method validation and the application of the method to real samples were carried out with 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl) imide. Under the optimum conditions, the calibration curve for zearalenone determination was linear in the range of 1–750 µg L−1(R2 = 0.9960) and the limit of detection was 0.25 µg L−1 for zearalenone. The inter-day and intra-day precisions of the developed method were in the range of 1.36–3.02%. The method was successfully applied to beer and cereal (wheat and corn) samples. The recovery percentages of zearalenone for spiked samples were between were 80.0 and 100.0%.

A combination of microextraction separation, preconcentration, and spectrophotometric detection for the determination of sodium dodecyl sulfate with quinaldine red

The optimal conditions for the microextraction separation, preconcentration, and spectrophotometric determination of sodium dodecyl sulfate (SDS) as an ion associate with quinaldine red are determined. The best extractants were found to be the mixtures of CCl4 with dichloroethane or chloroform; they ensure a 10- to 50-fold preconcentration of SDS from an aqueous medium into an organic microextract. We used cuvettes of special design to measure the absorbance of microextracts. A procedure for the extraction-spectrophotometric determination of anionic surfactants with the detection limit for SDS of 0.04 μg/mL is developed. The procedure was tested using wastewater samples.

Magnetic retrieval of ionic liquid formed during in situ metathesis dispersive liquid–liquid microextraction–preconcentration of selected endocrine disrupting phenols from an enlarged sample volume

A new in situ dispersive liquid–liquid microextraction procedure with magnetic retrieval of ionic liquid and quantification by LC-MS/MS has been presented. Selected endocrine disrupting phenols were determined.