Development of a new continuous homogenous liquid phase microextraction procedure based on in-situ preparation of deep eutectic solvent; application in the analysis of aliphatic amines in urine samples by GC-MS.

In the present work, a new microextraction procedure combined with gas chromatography-mass spectrometry has been developed for the analysis of several aliphatic amines from urine sample. The sample preparation method was a continuous homogenous liquid phase microextraction that was based on in-situ preparation of 4-chlorophenol: choline chloride deep eutectic solvent. The deep eutectic solvent was prepared by passing the mixture of related compounds through a syringe barrel filled with exothermic salts (calcium chloride and potassium bromide). The released heat by dissolving the salts and increasing the solution ionic strength assists the formation of the deep eutectic solvent. The influence of various factors on the efficiency of the proposed procedure including salts amount, flow rate, pH, salting-out effect, and extraction solvent volume was studied. The calibration curves were linear broadly over the concentration range of 1.2-250 ng mL-1 with coefficient of determinations ≥0.996. The enrichment factors were in the range of 188-246 and the limits of detection and quantification were 0.16-0.37 and 0.56-1.2 ng mL-1, respectively. Based on the results, the offered method was sensitive, rapid, eco-friendly, and efficient for extracting and determining aliphatic amines in urine samples.

Development of salt-induced homogeneous liquid-liquid extraction using a deep eutectic solvent performed in a narrow-bore tube for the extraction of Zn(II), Cu(II), and Cd(II) ions from honey samples.

In this study, a sample preparation procedure based on salt-induced homogeneous liquid-liquid extraction performed in a narrow-bore tube was used for the preconcentration and extraction of Zn(II), Cu(II), and Cd(II) ions from honey samples. To perform the procedure, a mixture of working solution containing sodium chloride, acetonitrile, and a synthesized deep eutectic solvent (as an extraction solvent) was transferred into a narrow tube filled with solid sodium chloride up to a specific level. As the solution flowed through the tube, tiny droplets of the extraction solvent were formed at the boundary between the solution and salt layer. The droplets moved upwards in the tube and eventually collected as a distinct layer on the top of the solution. The separated phase was removed and dispersed into ionized water. After centrifugation, tiny droplets of the extraction solvent containing the analytes were sedimented at the bottom of the tube. The concentrated analytes were measured using flame atomic absorption spectrophotometry. The linear ranges and extraction recoveries were obtained in the ranges of 1.5-100 µg kg-1 and 89.6-94.8%, respectively. The detection limits ranged from 0.35 to 0.48 µg kg-1. Low relative standard deviations (C = 10 µg L-1, n = 6) of 3.1, 2.8, and 3.4% for Zn(II), Cu(II), and Cd(II), respectively, were obtained. Finally, the optimized method was successfully used in determination of concentration of the selected heavy metal ions in various honey samples.

In-situ formation of the adsorbent based on octadecylamine for the extraction of Ag+ ions from aqueous solutions and its determination by microinjection flame atomic absorption spectrometry.

In this research, a dispersive solid phase extraction procedure based on changing the solubility of octadecylamine with pH was proposed to determine Ag+ ions in different water samples. For this purpose, first, the pH of sample solution containing the analyte was adjusted to 10.5. Then desired volume of the octadecylamine dissolved in acidic solution was injected into the solution. Because of the low solubility of octadecylamine in alkaline solution, a cloudy state was formed. The produced octadecylamine particles acted as a complexing agent for Ag+ ions and adsorbent for the formed complex. The obtained cloudy solution was centrifuged and the sedimented particles were removed and dissolved in a diluted nitric acid solution. It was injected into a flame atomic absorption spectrometry to determine the extracted amounts of the analyte. The effect of important parameters such as the amount of octadecylamine, volume of nitric acid, and centrifugation and vortexing conditions on the extraction efficiency of the procedure was studied and optimized. In optimal conditions, the developed method showed a linear range of 0.50-200 µg L-1. The limits of detection and quantification were 0.18 and 0.50 µg L-1, respectively. Extraction recovery was 93.6%. The relative standard deviations were less than 4%. The effectiveness of the method was investigated by determination of Ag+ ions in water and wastewater samples.

Determination of copper(II) and lead(II) ions in dairy products by an efficient and green method of heat-induced homogeneous liquid-liquid microextraction based on a deep eutectic solvent.

In this study, a new homogeneous liquid-liquid microextraction method using a deep eutectic solvent has been developed for the extraction of Cu(II) and Pb(II) ions in dairy products. Initially, the deep eutectic solvent was synthesized using choline chloride and p-chlorophenol and used as the extraction solvent. The synthesized solvent was soluble in milk at 70 °C and its separation from the sample was performed by decreasing the temperature. By cooling, a cloudy solution was formed due to the low solubility of the solvent at low temperatures. On centrifugation, the fine droplets of the solvent containing the analytes settled at the bottom of the tube by sedimentation. The enriched analytes were determined by flame atomic absorption spectrometry. The effect of some important parameters such as the amount of protein precipitating agent , complexing agent amount, extraction solvent volume, salt addition, pH, and temperature on the extraction efficiency of the method was studied and optimized. Under the optimal conditions, the linear ranges of the method for Cu(II) and Pb(II) ions were obtained in the ranges of 0.10-50 and 0.50-50 µg L-1 with detection limits of 0.04 and 0.18 µg L-1, respectively. The repeatability of the developed method, expressed as relative standard deviation, was determined to be 3.2 and 3.9% for Cu(II) and Pb(II) ions, respectively. Finally, by determining the concentration of Cu(II) and Pb(II) ions in milk, doogh, and cheese samples, the feasibility of the method was successfully confirmed with the extraction recoveries of 95.9 and 92.1% for Cu(II) and Pb(II) ions, respectively.

Using mandelic acid as an extraction solvent in the extraction of Cu(II) and Cd(II) from soil samples.

In this study, an efficient, green, and rapid sample preparation method based on mandelic acid dimer was proposed for the extraction of Cu(II) and Cd(II) from soil samples followed by flame atomic absorption spectrometry. In this research, for the first time, the liquid dimer was prepared by heating solid mandelic acid. Then the mixture of soil and a complexing agent was added into it. The mixture was transferred into a microwave oven. Diluted nitric acid solution as a dilution solvent was added. After centrifugation, two aliquots of the collected phase were removed and injected into the instrument. The relevant optimization parameters such as dimer volume, microwave exposure time, amount of complexing agent, and the type and volume of dilution solvent were investigated and optimized. Under the optimum conditions, detection limits were obtained 0.17 and 0.16 mg Kg-1 for Cu(II) and Cd(II), respectively. The linear ranges were 0.50-50 mg Kg-1 with coefficient of determination ≥ 0.9981. The developed method along with a reference method was applied for the analysis of the selected heavy metal ions in different soil samples and comparable results were obtained. Also, the method was performed on a certified reference material and the obtained concentrations compared with the certificated concentrations to assess accuracy of the proposed method.

Selective extraction of apixaban from plasma by dispersive solid-phase microextraction using magnetic metal organic framework combined with molecularly imprinted polymer nanocomposite.

This research aims to synthesize a specific and efficient sorbent to use in the extraction of apixaban from human plasma samples and its determination by high-performance liquid chromatography-tandem mass spectrometry. High specific surface area of metal-organic framework, magnetic property of iron oxide nanoparticles, selectively of molecular imprinted polymer toward the analyte, and the combination of dispersive solid-phase extraction method with a sensitive analysis system provided an efficient analytical method. In this study, first, a molecularly imprinted polymer combined with magnetic metal organic framework nanocomposite was prepared and then characterized using different techniques. Then the sorbent particles were used for selective extraction of the analyte from plasma samples. The efficiency of the method was improved by optimizing effective parameters. According to the validation results, wide linear range (1.02-200 ng mL-1 ), acceptable coefficient of determination (0.9938), low limit of detection (0.32 ng mL-1 ) and limit of quantification (1.02 ng mL-1 ), high extraction recovery (78%), and good precision (relative standard deviations ≤ 2.9% for intra- (n = 6) and interday (n = 6) precisions) were obtainable using the proposed method. These outcomes showed the high potential of the proposed method for screening apixaban in the human plasma samples.

In situ formation of chloroform for dispersive liquid-liquid microextraction of some aromatic amines from aqueous samples optimized by central composite design prior to GC-MS analysis.

In the current research, an in situ solvent formation-liquid phase microextraction method based on chloroform has been introduced as an efficient sample preparation procedure and applied for the extraction and preconcentration of some aromatic amines from wastewaters. In this method, chloral hydrate (2,2,2-trichloroethane-1,1-diol) was added to an alkaline solution of the samples in order to form chloroform as an extraction solvent in the sample solution. Thus, the selected analytes were transferred from the aqueous solution into the tiny droplets of the produced chloroform. Following this, the extracted and enriched analytes were quantified using a gas chromatograph-mass spectrometer. Experimental conditions of the proposed method including the chloral hydrate amount, salt effect, extraction time, and sodium hydroxide concentration were studied and optimized by a central composite design approach. By the offered method, high enrichment factors (292-324) with satisfactory extraction recoveries (82-91%), low limits of detection (0.26-0.39 ng mL-1), and proper repeatability (relative standard deviations ≤6.3% for intra- and inter-day precisions) were achieved under optimum conditions. Eventually, the suggested method was assessed through the quantification of aromatic amines in aqueous samples.

In-situ formation of a solid adsorbent for the extraction of some metal ions from crude oil before their determination by microflow nebulizer inductively coupled plasma-mass spectrometry.

The presence of heavy metals in crude oil can create different problems on the oil processing and devices as well as pollution of the environment. Establishment of sample preparation methods for the extraction of metals from crude oil is the bottleneck of a successful determination method due to high hydrophobicity and complexity of crude oil matrix. In this study, a dispersive solid phase extraction procedure was developed for the simultaneous extraction of sixteen metal ions based on in-situ formation of an adsorbent in the sample solution. For this purpose, a suitable amount of dithiooxamide was dissolved in an organic solvent and was injected into the sample solution. By this action, dithiooxamide was re-precipitated in the sample solution and adsorbed the ions. The solid particles were separated and then the ions were eluted by a few microliters of choline chloride: 5-amino-8-hydroxyquinoline deep eutectic solvent under sonication. The presented method was validated and broad linear ranges (7.56-50000 ng g-1) were obtained for calibration curves with coefficient of determination ≥0.992. Acceptable limits of detection (0.003-2.32 ng g-1) and quantification (0.009-7.56 ng g-1) were achieved. Good precision (relative standard deviation less than or equal to 4.3% for intra and inter-day precisions) and acceptable extraction recoveries (66-91%) were also obtained. Seven crude oil samples were analyzed and ten metal ions were determined successfully. The method was compared with the methods reported in literature and it was found that the data obtained by this method were reliable and accurate.

Development of a pH-induced dispersive solid-phase extraction method using folic acid combined with dispersive liquid-liquid microextraction: application in the extraction of Cu(II) and Pb(II) ions from water and fruit juice samples.

In this study, a new pH-induced dispersive solid-phase extraction method using folic acid has been proposed for the extraction of Cu(II) and Pb(II) ions from water and fruit juice samples. For this purpose, at first, a specified amount of folic acid was dissolved in the sample solution containing the studied ions at pH 8.5. Then, by decreasing pH of the solution, solubility of folic acid reduced and its fine particles containing the analytes were produced. They were separated and dissolved in dimethylformamide. For more preconcentration, the developed procedure was combined with a dispersive liquid-liquid microextraction procedure. Finally, the extracted and enriched analytes were determined by flame atomic absorption spectrometry. The effect of important parameters on the extraction efficiency of the method such as pH, folic acid amount, the amount of complexing agent, dimethylformamide volume, ionic strength, and centrifugation conditions were studied. Under optimized conditions, the developed method showed linear ranges of 0.20-40 and 0.25-40 µg L-1 for Pb(II) and Cu(II) ions, respectively. Limits of detection of Pb(II) and Cu(II) were 0.07 and 0.08 µg L-1, respectively. The relative standard deviations (intra- and inter-day precisions) were between 3.8 and 5.4%. Accuracy of the proposed method was studied by determination of the analytes concentrations in a certified reference material; SPS-WW2 Batch 108. Efficiency of the proposed procedure was evaluated by analyzing Pb(II) and Cu(II) ions in various water and fruit juice samples.

Riboflavin as a green sorbent in dispersive micro-solid-phase extraction of several pesticides from fruit juices combined with dispersive liquid-liquid microextraction.

A vortex-assisted dispersive micro-solid-phase extraction procedure using a new and green sorbent was developed as a simple, fast, and efficient sample preparation method for the extracting five pesticides in several fruit juice samples. In this study, for the first time, riboflavin was used as an efficient sorbent. A few milligrams of riboflavin was directly added into the aqueous solution containing the analytes to adsorb them. After adsorption the analytes, they were desorbed and more concentrated by a dispersive liquid-liquid microextraction procedure. The influence of several effective parameters such as amount of riboflavin, pH, vortex time, eluent nature and volume, and extraction solvent type and volume on the extraction efficiency was investigated. In optimal conditions, linear ranges of the calibration curves were broad. The limits of detection and quantification were attained in the ranges of 0.56-1.5  and 1.9-0.52 ng mL-1 , respectively. The proposed method demonstrated to be suitable for concurrent extraction of the studied pesticides in various fruit juice samples with high enrichment factors (320-360) and precision (relative standard deviation ≤7.8% for intra- [n = 6] and interday [n = 4] precisions at a concentration of 25 ng mL-1 of each pesticide).

Improved magnetic solid-phase extraction based on magnetic sorbent obtained from sand for the extraction of pesticides from fruit juice.

BACKGROUND: A combination of magnetic solid-phase extraction using an efficient and cheap magnetic sorbent obtained from sand and dispersive liquid-liquid microextraction has been developed for the extraction of nine multiclass pesticides (clodinafop-propargyl, haloxyfop-R-methyl, fenoxaprop-P-ethyl, oxadiazon, penconazole, diniconazole, chlorpyrifos, fenazaquin, and fenpropathrin) from commercial fruit juices (sour cherry, pomegranate, grape, watermelon, orange, apricot, and peach juices). The enriched pesticides were determined by gas chromatography-flame ionization detector and gas chromatography-mass spectrometry. The sorbent was natural iron oxide entrapped in silica along with some impurities. In this method, to extract the analytes from the samples, an appropriate amount of the magnetic sorbent (at mg level) is added. Then the sorbent particles are isolated from the solution using an external magnetic field and the adsorbed analytes are desorbed from the sorbent by acetone. In the following, a dispersive liquid-liquid microextraction procedure is carried out to concentrate the analytes more and to reach low limits of detection. RESULTS: Under optimized extraction conditions, the method revealed satisfactory repeatability (relative standard deviation ≤8% for intra-day and inter-day precision), reasonable extraction recovery (43.3-55.9%), high enrichment factors (433-559), and low limits of detection (0.45-0.89 µg L-1 ). CONCLUSION: The method was applied in the analysis of pesticides in various fruit juices. Chlorpyrifos was found in peach juice at a concentration of 27 ± 2 µg L-1 (n = 3) using a gas chromatography-flame ionization detector. To verify the results, the peach juice was also injected into gas chromatography-mass spectrometry after applying the proposed extraction method. © 2022 Society of Chemical Industry.

Development of a liquid-nitrogen-induced homogeneous liquid-liquid microextraction of Co(II) and Ni(II) from water and fruit juice samples followed by atomic absorption spectrometry detection.

In this study, a simple and rapid sample preparation method named liquid-nitrogen-induced homogeneous liquid-liquid microextraction has been developed for the extraction and pre-concentration of Co(II) and Ni(II) ions before their analysis by flame atomic absorption spectrometry. For this purpose, first, acetonitrile containing 8-hydroxyquinoline is added into a sample solution and the mixture is vortexed. As a result, a homogeneous solution is formed. Subsequently, the solution is cooled using liquid nitrogen for a few seconds. By this process, due to difference in the freezing point of acetonitrile and water, the homogeneous state is broken and the analytes (as oxinate complexes) are extracted into liquid acetonitrile phase collected on top of the frozen aqueous phase. The linear dynamic ranges obtained for Ni(II) and Co(II) were 1.0-30 and 0.50-20 µg L-1, respectively. The obtained limits of detection were 0.36 and 0.20 µg L-1 for Ni(II) and Co(II), respectively.

Development of a dispersive liquid-liquid microextraction method based on a ternary deep eutectic solvent as chelating agent and extraction solvent for preconcentration of heavy metals from milk samples.

A simple, green, rapid, and efficient ligandless dispersive liquid-liquid microextraction procedure based on solidification of a ternary deep eutectic solvent has been proposed for the extraction of trace amounts of Cd(II), Cu(II), and Pb(II) ions in milk samples prior to their determination by flame atomic absorption spectrometry. Initially, a suitable mole ratio of sorbitol, menthol, and mandelic acid are mixed in a test tube, and after heating, a deep eutectic solvent with low density compared to water is formed. The synthesized solvent is used as a chelating agent and an extraction solvent in the extraction of some heavy metal ions from milk samples. The influence of several effective parameters on the responses and extraction recoveries of the analytes was investigated. Under the optimum experimental conditions, the linear ranges were in the ranges of 1.0-40 µg L-1 for Cd(II) and Pb(II), and 1.0-25 µg L-1 for Cu(II). The obtained relative standard deviations (n = 6, C = 2.5 µg L-1 of each cation) and detection limits were in the ranges of 3.4-4.1% and 0.38-0.42 µg L-1, respectively. Finally, the developed method was successfully applied for the determination of Cd(II), Cu(II), and Pb(II) ions in different milk samples.

Application of a clean-up procedure using a ternary liquid phase system combined with pre-concentration by microextraction in the analysis of seven pesticides from soya milk.

BACKGROUND: A method has been developed based on a three-phase system, followed by dispersive liquid-liquid microextraction for the extraction of seven pesticides from soya milk prior to analysis by gas chromatography-flame ionization detection. The base of this method is the different extraction capability of the components of soya milk according to each of the phases involved. In this procedure, a homogeneous solution consisting of soya milk and a water-miscible solvent (acetonitrile) is separated into two phases in the presence of Na2 SO4 and the analytes are extracted into the produced acetonitrile droplets. The acetonitrile phase is mixed with a pre-concentration solvent to perform the next microextraction procedure for further enrichment of the analytes. RESULTS: Limits of detection and quantification were reached in the ranges of 0.11-0.35 and 0.35-1.20 µg L-1 , respectively. Enrichment factors and extraction recoveries were in the ranges of 562-933 and 56-93%, respectively. Relative standard deviations were ≤7% for intra- (n = 6) and inter-day (n = 5) precisions at two concentrations of 10 and 50 µg L-1 of each analyte. CONCLUSION: The proposed method was applied to the analysis of pesticides in soya milk samples at µg L-1 concentrations. © 2019 Society of Chemical Industry.

Cyclohexylamine as extraction solvent and chelating agent in extraction and preconcentration of some heavy metals in aqueous samples based on heat-induced homogeneous liquid-liquid extraction.

A new sample preparation method has been developed for extraction and preconcentration of some heavy metal cations in aqueous samples using cyclohexylamine-based homogeneous liquid-liquid microextraction. In the proposed method, cyclohexylamine was used as both the complexing agent and the extraction solvent. For this purpose, cyclohexylamine at µL level was initially added into an aqueous solution containing Co(II), Ni(II), and Cu(II) ions which was placed in a glass test tube. The mixture was shaken for forming a homogeneous solution. Then sodium chloride was added to the solution. After shaking manually again, the test tube was placed in a water bath thermostated at 70°C. Due to lower solubility of cyclohexylamine at the elevated temperature, a cloudy solution was formed. The fine droplets of cyclohexylamine containing cation-cyclohexylamine complexes were collected on the top of the aqueous phase by centrifuging. The enriched analytes in the upper phase were determined by graphite furnace atomic absorption spectrometry. Several variables possibly affecting the extraction efficiency were investigated and optimized. Under the optimum conditions the calibration curves were linear in the ranges of 80-1000, 40-700, and 80-800ngL-1 for Co2+, Ni2+, and Cu2+, respectively. Repeatability of the proposed method, expressed as relative standard deviation, ranged from 3.3% to 5.2% (n = 6, C = 200ngL-1). Moreover, the obtained detection limits of the selected analytes were in the range of 15.3-37.7ngL-1. The accuracy of the developed procedure was verified by analyzing a certified reference material, namely NRCC-SLRS4 Riverine water. Finally, the proposed method was successfully applied for the simultaneous analysis of the selected analytes in environmental water samples.

Microextraction methods for the determination of phthalate esters in liquid samples: A review.

1,2-Benzenedicarboxylic acid esters, commonly referred to as phthalate esters, form a group of compounds that are mainly used as plasticizers in polymers. Because phthalate esters are not chemically bound to the plastics, they can be released easily from products and migrate into the food or water that comes into direct contact. Due to their widespread use, they are considered as ubiquitous environmental pollutants. Phthalate esters are regarded as endocrine disrupting compounds by means of their carcinogenic effect. Phthalate esters can be analyzed by gas chromatography or high-performance liquid chromatography, however, their sensitivity and selectivity limit their direct use for determination of phthalates at very low level of concentrations exist in environmental samples with complex matrices. Therefore a sample pretreatment prior to their analysis is necessary. In this review, the historical development and overview of sample preparation methodologies have briefly been discussed and a comprehensive application of these methods in combination with different analytical techniques for preconcentration and determination of phthalate esters in various matrices have been summarized. Finally, a critical comparison of the different approaches in terms of enrichment factors achieved, extraction efficiency, precision, selectivity and simplicity of operation is provided.

Molecularly imprinted-solid phase extraction combined with simultaneous derivatization and dispersive liquid-liquid microextraction for selective extraction and preconcentration of methamphetamine and ecstasy from urine samples followed by gas chromatography.

In this study, a developed technique was reported for extraction and pre-concentration of methamphetamine (MAMP) and 3,4-methylenedioxymethamphetamine (MDMA, ecstasy) from urine samples using molecularly imprinted-solid phase extraction (MISPE) along with simultaneous derivatization and dispersive liquid-liquid microextraction (DLLME). Molecularly imprinted microspheres as sorbent in solid phase extraction (SPE) procedure were synthesized using precipitation polymerization with MAMP as the template. Aqueous solution of the target analytes was passed through MAMP-MIP cartridge and the adsorbed analytes were then eluted with methanol. The collected eluate was mixed with butylchloroformate which served as the derivatization reagent as well as the extraction solvent. The mixture was immediately injected into deionized water. After centrifugation, 1 µL of the settled organic phase was injected into gas chromatography-flame ionization detection (GC-FID) or gas chromatography-mass spectrometry (GC-MS). Various experimental parameters affecting the performance of both of the steps (MISPE and DLLME) were thoroughly investigated. The calibration graphs were linear in the ranges of 10-1500 ng mL(-1) (MAMP) and 50-1500 ng mL(-1) (MDMA), and the detection limits (LODs) were 2 and 18 ng mL(-1), respectively. The relative standard deviations (%RSDs) obtained for six repeated experiments (100 ng mL(-1) of each drug) were 5.1% and 6.8% for MAMP and MDMA, respectively. The relative recoveries obtained for the analytes in human urine samples, spiked with different levels of each drug, were within the range of 80-88%.