Dispersive Liquid–Liquid Microextraction of Silver Prior to Determination by Microsample Introduction-Flame Atomic Absorption Spectrometry

Abstract

A new simple and sensitive method has been proposed for rapid determination of trace levels of silver in environmental water samples, using dispersive liquid–liquid microextraction (DLLME) prior to its microsample introduction-flame atomic absorption spectrometry. Under the optimum conditions, the linear range was 0.1–7 µg L^?1 and limit of detection was 0.018 µg L^?1. The relative standard deviation for 0.50 and 5.00 µg L^?1 of silver in water sample was 4.0 and 1.7%, respectively. The relative recoveries of silver from tap, well, river, and seawater samples at spiking levels of 1.00 and 5.00 µg L^?1 were in the range of 86.4–98.6%.     

Preconcentration and Determination of Chromium Species Using Octadecyl Silica Membrane Disks and Flame Atomic Absorption Spectrometry

A novel and selective method for the fast determination of trace amounts of chromium species in water samples has been developed. The procedure is based on the selective formation of chromium diethyldithiocarbamate complexes at different pH in the presence of Mn(II) as an enhancement agent of chromium signals followed by elution with organic eluents and determination by atomic flame absorption spectrometry. The maximum capacity of the employed disks was found to be (396±3) µg and (376±2) µg for Cr(III) and Cr(VI), respectively. The detection limit of the proposed method is 49 and 43 ng·L^?1 for Cr(III) and Cr(VI), respectively. The proposed method was successfully applied for determination of chromium species Cr(III) and Cr(VI) in different water samples.     

Dispersive Liquid–Liquid Microextraction of Nickel Prior to Its Determination by Microsample Injection System-Flame Atomic Absorption Spectrometry

A sensitive and simple method for the determination of trace nickel was developed by the combination of dispersive liquid–liquid microextraction (DLLME) and microsample injection system–flame atomic absorption spectrometry (MIS–FAAS). Trace nickel was preconcentrated as the 8-hydroxyquinoline chelate by DLLME, and the conditions were optimized by a Plackett-Burman design. Quantitative recovery of nickel (98 ± 1%) was obtained by a sample volume of 7.5 mL at a pH of 6.0. The enrichment factor was 52.5, and the limits of detection and quantitation were 0.1 µ g L^?1 and 3.0 µ g L^?1, respectively. The method was validated by the analysis of a wastewater standard reference material, water samples, and a wire sample. The reported method has superior analytical figures of merit compared with similar methods reported in the literature.     

Preconcentration and Determination of Trace Amounts of Heavy Metals in Water Samples Using Membrane Disk and Flame Atomic Absorption Spectrometry

A fast and simple method for preconcentration of Ni^2＋, Cd^2＋, Pb^2＋, Zn^2＋, Cu^2＋ and Co^2＋ from natural water samples was developed. The metal ions were complexed with sodium diethyldithiocarbamate （Na-DDTC）, then adsorbed onto octadecyl silica membrane disk, recovered and determined by FAAS. Extraction efficiency, influence of sample volume and eluent flow rates, effects of pH, amount of Na-DDTC, nature and amount of eluent for elution of metal ions from membrane disk, break through volume and limit of detection have been evaluated. The effect of foreign ions on the percent recovery of heavy metal ions has also been studied. The limit of detection of the proposed method for Ni^2＋, Cd^2＋, Pb^2＋, Zn^2＋, Cu^2＋ and Co^2＋was found to be 2.03, 0.47, 3.13, 0.44, 1.24 and 2.05 ng·mL^-1, respectively. The proposed （DDTC） method has been successfully applied to the recovery and determination of heavy metal ions in different water samples.     

Ligandless,Task-Specific Ionic Liquid-Based Ultrasound-Assisted Dispersive Liquid–Liquid Microextraction for the Determination of Cobalt Ions by Electrothermal Atomic Absorption Spectrometry

Ligandless, task-specific ionic liquid based ultrasound-assisted dispersive liquid–liquid microextraction (TSIL-USA-DLLME) was used for preconcentration of cobalt ions in food and water samples and in vitamin supplements before analysis by electrothermal atomic absorption spectrometry. The reported method is free of toxic volatile organic solvents and does not require the use of a back-extraction step. The dispersion of extractant was achieved with the use of ultrasound. A TSIL, trioctylmethylammonium thiosalicylate (TOMATS), was served as both the extraction and complexing agent. After microextraction, the TOMATS phase was separated by centrifugation and dissolved in ethanol before analysis. Selected parameters affecting the microextraction including the pH of the sample, the volume of the ionic liquid, the ultrasonication time, centrifugation parameters, and the influence of ionic strength were optimized. The limit of detection was 0.011?ng?mL^?1 for cobalt ions. The achieved preconcentration factor was 24. The relative standard deviations for the determination of analyte in the real samples were 3–24%. The accuracy of this method was evaluated by the extraction and determination of the analyte in several certified reference materials including INCT-SBF-4 (soya bean flour), INCT-TL-1 (tea leaves), ERM-CAO11b (hard drinking water), INCT-MPH-2 (mixed Polish herbs), TMDA-54.5 (Lake Ontario Water), and NIST 1643e. The measured cobalt contents were in satisfactory agreement with the certified concentrations based on Student’s t-test at the 95% confidence level. The presented method has been successfully applied for the determination of analyte in real samples that include tea, lake water, and vitamin supplements.     

Speciation of Arsenic in Drinking Water by Dispersive Liquid–Liquid Microextraction,Graphite Furnace Atomic Absorption Spectrometry,and Orthogonal Array Design

Orthogonal array design was used to optimize arsenic speciation in drinking water in contact with materials by dispersive liquid–liquid microextraction followed by graphite furnace atomic absorption spectrometry. Arsenic speciation was achieved by the formation of an arsenic(III) hydrophobic complex with a new chelating agent, 1,2,6-hexanetriol trithioglycolate, at neutral pH. The complex was extracted into the organic phase, while arsenic(V) remained in aqueous solution. The concentration of As(V) was determined by subtracting As(III) from the total arsenic following the reduction of As(V) to As(III) by L-cysteine. Orthogonal array design with OA₁₆ (44) and OA₉ (33) matrices was used to optimize the efficiency of dispersive liquid–liquid microextraction and the reduction of As(V) to As(III), respectively. Under the optimal conditions, the detection limit was 0.03?µg?L^?1 for As(III) and the relative standard deviation was 5.9% with an enhancement factor of 87. The calibration curve was linear from 0.19 to 3.0?µg?L^?1 with a correlation coefficient of 0.9996. The developed method was used for arsenic speciation in solutions of drinking water that contacted materials. The recoveries of fortified samples were in an acceptable range from 92.0 to 113.3%.     

LC Determination of Chloramphenicol in Honey Using Dispersive Liquid–Liquid Microextraction

A novel method, dispersive liquid–liquid microextraction coupled with liquid chromatography-variable wavelength detector (LC-VWD), has been developed for the determination of chloramphenicol (CAP) in honey. A mixture of extraction solvent (30 μL 1,1,2,2-tetrachloroethane) and dispersive solvent (1.00 mL acetonitrile) were rapidly injected by syringe into a 5.0 mL real sample for the formation of cloudy solution, the analyte in the sample was extracted into the fine droplets of C₂H₂Cl₄. After extraction, phase separation was performed by centrifugation and the enriched analyte in the sedimented phase was determined by LC-VWD. Some important parameters, such as the kind and volume of extraction solvent and dispersive solvent, extraction time, sample solution pH, sample volume and salt effect were investigated and optimized. Under the optimum extraction condition, the method yields a linear calibration curve in the concentration range from 3 to 2,000 μg kg^?1 for target analyte. The enrichment factor for CAP was 68.2, and the limit of detection (S/N = 3) were 0.6 μg kg^?1. The relative standard deviation (RSD) for the extraction of 10 μg kg^?1 of CAP was 4.3% (n = 6). The main advantages of method are high speed, high enrichment factor, high recovery, good repeatability and extraction solvent volume at μL level. Honey samples were successfully analyzed using the proposed method.     

Determination of Antimony(III) and Total Antimony in Aqueous Samples by Electrothermal Atomic Absorption Spectrometry After Dispersive Liquid–Liquid Microextraction (DLLME)

Dispersive liquid–liquid microextraction (DLLME) technique combined with electrothermal atomic absorption spectrometry (ET-AAS) was proposed for determination of antimony(III) and total antimony at very low concentrations in water samples. The N-benzoyl-N-phenylhydroxylamine (BPHA) was used as a chelating agent, and chloroform and ethanol were used as extraction and disperser solvents, respectively. The effect of various experimental parameters on the extraction and determination was investigated. The detection limits (3σ) were 0.005 μg L^?1 for Sb(III) and 0.008 μg L^?1 for total Sb. The developed method was applied successfully to the determination of Sb(III) and total Sb in natural water samples.     

Determination of Phthalate Esters in Wine Using Dispersive Liquid–Liquid Microextraction and Gas Chromatography

A simple and rapid efficient method was developed for the determination of phthalate esters using dispersive liquid–liquid microextraction followed by gas chromatography with flame ionization detection. A mixture of isopropanol (0.75 mL, dispersant) and carbon tetrachloride (30 µL, extractant) with sodium chloride (1%, w/v) was used for extraction. Under optimum conditions, the method provided linear calibration curves between 0.5 and 200 µg L^?1 for dibutyl phthalate, and 1.0 and 200 µg L^?1 for butyl benzyl phthalate, diethyl phthalate, and diisooctyl phthalate. The relative standard deviations for intra-day and inter-day analyses were less than 5.8% and 6.9%, respectively, with enrichment factors between 229 and 424. Two wine samples were analyzed with recoveries between 70.1% and 119.3%.     

Sensitive and Accurate Determination of Cobalt at Trace Levels by Slotted Quartz Tube-Flame Atomic Absorption Spectrometry Following Preconcentration with Dispersive Liquid–Liquid Microextraction

Slotted quartz tube-flame atomic absorption spectrometry (SQT-FAAS) was used as a sensitive technique for the determination of cobalt, an element has toxic effects on living organisms at high doses. For the preliminary preconcentration of cobalt prior to the analysis, dispersive liquid–liquid microextraction (DLLME) was used. The instrument is equipped with a SQT to further increase the sensitivity by increasing the residence time of cobalt atoms in the light path emitted by a hollow cathode lamp. In the complex formation step, pH, the volume of buffer solution, the concentration of 1,5-diphenylcarbazone, and the volume of ligand were optimized. In addition, all of the system parameters, including the type and volume of the extraction solvent, dispersant type and volume of solvent, type of salt and the volume for the dispersion liquid–liquid microextraction, were optimized to obtain the lowest detection limit. Under the optimum conditions, the detection power of FAAS was improved by a factor of 86.56 fold using DLLME-SQT-FAAS. The limit of detection for the DLLME-SQT-FAAS system was 0.97?µg L^?1. The applicability of the developed method was verified in tap and waste water samples by spiking measurements. The percentage recovery values for these were determined to be 91.7% and 111.0%, respectively.     

Accurate and Precise Determination of Gold in Plating Bath Solution: Deep Eutectic Solvent Based Liquid Phase Microextraction – Slotted Quartz Tube – Flame Atomic Absorption Spectrometry

Abstract

A sensitive, simple and green deep eutectic solvent based liquid phase microextraction (DES-LPME) method is described for the quantification of trace gold by flame atomic absorption spectrometry with a slotted quartz tube (SQT-FAAS). A 1:2 choline chloride:phenol mixture was utilized as the DES for the extraction of gold from the aqueous solution. All of the parameters affecting the extraction efficiency were optimized to increase the detection power of the FAAS. Under the optimum conditions, the presented method provided a linear range between 15 and 400?µg/L with limits of detection and quantification of 5.1 and 16.9?µg/L, respectively. An approximate 58-fold improvement was obtained in the detection power of the FAAS based on the limit of detection using the optimized DES-LPME-SQT-FAAS method. In order to check the validity/applicability of the method, recovery measurements were performed for spiked gold plating bath samples and the resulting recoveries were between 105.3% and 107.6%. The presented method was employed for real sample analysis.     

Determination of Phthalates in Milk by Ultrasound-Assisted Dispersive Liquid–Liquid Microextraction and Gas Chromatography–Mass Spectrometry

Ultrasound-assisted dispersive liquid–liquid microextraction was coupled with gas chromatography—mass spectrometry for the determination of phthalate esters in milk. Dimethyl phthalate, diethyl phthalate, dibutyl phthalate, benzyl butyl phthalate, bis(2-ethylhexyl) phthalate, and dioctyl phthalate were analyzed in five brands of pasteurized Turkish milk. The efficiencies of the extraction procedure for the analytes were between 66 and 100%. The linear dynamic ranges of the calibration curves were from 0.025 to 1.000 µg/mL with correlation coefficients exceeding 0.99. The precision of the method is acceptable with relative standard deviation values below 5%. Dibutyl phthalate and bis(2-ethylhexyl) phthalate were commonly observed in milk.     

Determination of Tetracyclines in Milk,Eggs and Honey Using in-situ Ionic Liquid Based Dispersive Liquid–Liquid Microextraction

In this study, in-situ ionic liquid based dispersive liquid?liquid microextraction method for enrichment of tetracyclines before liquid chromatographic analysis has been improved. A 1-benzyl-3- methylimidazolium chloride was used as an ionic liquid. To increase extraction efficiency, some optimization parameters (amount of ammonium hexafluorophoshate, extraction time, centrifugation time, ratio of ionic liquid/salt) were investigated. At optimized conditions, enrichment factors of four tetracycline antibiotics (tetracycline, chlortetracycline, methacycline, doxycycline) were between 25 and 98. The residues of tetracyclines were not found in the studied real samples. For the accuracy of the method, the concentration of 50 and 250 μg/L of standard tetracycline mixture solutions were spiked to the blank real milk, honey and egg samples and the percentage recoveries were obtained in the range of 75.8–109.7%.     

Novel and Rapid Deep Eutectic Solvent (DES) Homogeneous Liquid–Liquid Microextraction (HLLME) with Flame Atomic Absorption Spectrometry (FAAS) Detection for the Determination of Copper in Vegetables

Novel and fast deep eutectic solvent (DES)-based homogeneous liquid–liquid microextraction (HLLME) was applied for the extraction of copper from vegetable samples followed by flame atomic absorption spectrometry (FAAS). 1,5-diphenyl carbazone (DPC) was used as the chelating agent, and a DES was used as the extraction media. The utilized DES was based on benzyl triphenyl phosphonium bromide and ethylene glycol in a 1:8?mole ratio. The phase separation phenomenon was occurred by changing of sample temperature. Several factors influencing the extraction efficiency were investigated and optimized. Under the optimized conditions, an enhancement factor of 64 was obtained. The limit of detection, based on three signal-to-noise ratio, and limit of quantification were found to be 0.13?µg L^?1 and 5.0?µg L^?1, respectively. The calibration curve was linear within the range of 5.0–250?µg L^?1 with r² > 0.9957. Intra- and inter-day relative standard deviations (%) of 2.1% and 2.6% were obtained at the concentration of 25?µg L^?1. The accuracy of the proposed method was evaluated by analyzing a tomato leaves certified reference material and the results were to be in agreement with the certified value. Finally, the feasibility of the method was successfully confirmed by determination of copper in spinach, lettuce, broccoli, potato, carrot and parsley samples.     

Preconcentration and Determination of Copper（Ⅱ） Using Octadecyl Silica Membrane Disks Modified by 1,5-Diphenylcarhazide and Flame Atomic Absorption Spectrometry

A simple and reproducible method for the rapid extraction and determination of trace amounts of copper（Ⅱ） ions using octadecyl-bonded silica membrane disks modified by 1,5-diphenylcarbazide （DPC） and atomic absorption spectrometry was presented, which was based on complex formation on the surface of the ENVI-18 DISK^TM disks followed by stripping of the retained species by minimum amounts of appropriate organic solvents. The elution was efficient and quantitative. The effect of potential interfering ions, pH, ligand amount, stripping solvent, and sample flow rate were also investigated. Under the optimal experimental conditions, the break-through volume was found to be about 1000 mL providing a preconcentration factor of 400. The maximum capacity of the disks was found to be （255±5） lag for Cu^2＋, and the limit of detection of the proposed method was 5 ng per 1000 mL. The method was applied to the extraction and recovery of copper in different water samples.     

Trace Determination of Manganese in Urine by Graphite Furnace Atomic Absorption Spectrometry and Inductively Coupled Plasma–Mass Spectrometry

This paper describes a simple and sensitive method for the determination of manganese in human urine by graphite furnace atomic absorption spectroscopy (GFAAS), which includes sample preparation by microwave digestion. Matrix modifier combinations, the digestion power, pyrolysis, and atomization temperatures were optimized. A mixture of 5.0 µg Pd(NO₃)₂ and 3.2 µg Mg(NO₃)₂ modifier presented the best performance. The optimal temperatures for pyrolysis and atomization were 1500°C and 1950°C, respectively. The GFAAS method was compared to inductively coupled plasma–mass spectrometry (ICP–MS) for the determination of manganese in urine. Analytical figures of merit for GFAAS and ICP–MS were: accuracy (3.46%, 2.19%), precision (3.61%, 5.84%), LOD (0.109 µg · L^?1, 0.015 µg · L^?1), LOQ (0.327 µg · L^?1, 0.045 µg · L^?1), and recovery (80–100%, 74–89%). Both methods were employed for the determination of Mn in urine and the results were compared statistically.     

Ultra-Preconcentration and Determination of Multiple Pesticide Residues in Water Samples Using Ultrasound-Assisted Dispersive Liquid–Liquid Microextraction and GC-FID

In this study, a simple and efficient method has been developed to analyze pesticides in water samples using ultrasonic-assisted dispersive liquid–liquid microextraction (UA-DLLME) combined with gas chromatography-flame ionization detection (GC-FID). Several parameters, including type and volume of extractant and dispersant, extraction time, and amount of salt on extraction performance, were optimized in detail. A mixture of acetonitrile (1.0 mL, dispersant) and carbon tetrachloride (15 μL, extractant) was used for extraction. Under optimal conditions, enrichment factors were obtained between 315 and 1153. The linearity of the method ranged from 1 to 100 μg L⁻¹ with correlation coefficients ≥0.9990. Limits of detection (S/N = 3) ranged between 0.09 and 0.57 μg L⁻¹, depending on the compounds. Relative standard deviations were <8.0 % (n = 5) for both intra- and inter-day analyses. The proposed method was successfully applied for the preconcentration and determination of pesticides in water samples (river water, tap water, and lake water) with recoveries that varied from 90.5 to 107.7 %.

     

Ultra-Preconcentration and Determination of Multiple Pesticide Residues in Water Samples Using Ultrasound-Assisted Dispersive Liquid–Liquid Microextraction and GC-FID

In this study, a simple and efficient method has been developed to analyze pesticides in water samples using ultrasonic-assisted dispersive liquid–liquid microextraction (UA-DLLME) combined with gas chromatography-flame ionization detection (GC-FID). Several parameters, including type and volume of extractant and dispersant, extraction time, and amount of salt on extraction performance, were optimized in detail. A mixture of acetonitrile (1.0 mL, dispersant) and carbon tetrachloride (15 μL, extractant) was used for extraction. Under optimal conditions, enrichment factors were obtained between 315 and 1153. The linearity of the method ranged from 1 to 100 μg L^?1 with correlation coefficients ≥0.9990. Limits of detection (S/N = 3) ranged between 0.09 and 0.57 μg L^?1, depending on the compounds. Relative standard deviations were <8.0 % (n = 5) for both intra- and inter-day analyses. The proposed method was successfully applied for the preconcentration and determination of pesticides in water samples (river water, tap water, and lake water) with recoveries that varied from 90.5 to 107.7 %.     

Rapid Extraction of Imidacloprid in Tomatoes by Ultrasonic Dispersion Liquid–Liquid Microextraction Coupled with LC Determination

A simple method for the extraction and determination of trace imidacloprid in tomatoes was developed using ultrasonic dispersion liquid–liquid microextraction coupled with liquid chromatographic separation. An ultrasonic dispersion process was applied to accelerate the formation of the fine cloudy solution without using disperser solvents, which was markedly increased the extraction efficiency and reduced the equilibrium time. The results revealed that tetrachloroethane as extraction solvent could be directly applied to the filtered tomato juice with the assistance of ultrasonic dispersion. Under the optimum condition, the enrichment factor of imidacloprid could reach 375 folds and the average recovery of samples ranged from 87.6 to 110% with RSD less than 4.5% (n = 3). Compared to the conventional sample pretreatment method, the proposed method had the advantage of short time, simple operation, high sensitivity and low consumption of organic solvent.     

Preconcentration and Determination of Chlorophenols in Wastewater with Dispersive Liquid–Liquid Microextraction Using Hydrophobic Deep Eutectic Solvents

Abstract

Hydrophobic deep eutectic solvents (DESs) were synthesized and developed for the preconcentration of three chlorophenols from wastewater by dispersive liquid–liquid microextraction (DLLME). The analyte concentrations were determined by high-performance liquid chromatography (HPLC). The hydrophobic DESs were prepared with the combination of hydrogen bond donors of decanoic acid or octanoic acid with different hydrogen bond acceptors of quaternary ammonium salts of tetrabutylammonium chloride, tetraoctylammonium chloride, methyltrioctylammonium chloride, and tetraheptylammonium chloride). Following the study of the stability and characterization by Fourier transform infrared spectroscopy, the hydrophobic DESs were developed as extractants and employed for the removal of 4-chlorophenol (4-CP), 2,4-dichlorophenol (2,4-DCP), and 2,4,6-trichlorophenol (2,4,6-TCP) from wastewater. Using hydrophobic DESs as the microextraction solvents, several key parameters were optimized, including the type and volume of the hydrophobic DES, pH, and time of the extraction procedure. Under the optimized conditions, good recoveries from 90.8% to 93.0% were obtained for the three chlorophenols. The limits of detection were less than 0.05?µg/mL with relative standard deviations between 1.8% and 3.1%. The method was applied for the isolation and determination of synthetic chlorophenols in wastewater.