Low-density Organic Solvent Research Articles

Effervescent powder-assisted floating organic solvent-based dispersive liquid-liquid microextraction for determination of organochlorine pesticides in water by GC–MS

An effervescent powder-assisted floating organic solvent-based dispersive liquid-liquid microextraction was introduced for determination of 13 organochlorine pesticides in water samples. In this method, a less toxic low-density organic solvent was used as extraction solvent. The extraction solvent was dispersed in to the aqueous sample via CO2 bubbles, in-situ generated up on addition of water to a falcon tube containing the mixture of effervescent powder precursors as well as the extraction solvent. Various experimental parameters such as effervescent and its weight fractions, extraction solvent type and its volume, the total mass of effervescent precursors, and the effect of salt were investigated and the optimal conditions were established. Under the optimum conditions, the proposed method exhibited good linearity for all target pesticides with the coefficient of determinations varying from 0.9981 to 0.9997. The limits of detection and quantification were within the range of 0.03–0.24 and 0.26–0.75 μg/L, respectively. The intra- and inter-day precisions which were expressed in terms of the relative standard deviation ranged from 0.33 to 4.47 and 0.51–5.52%, respectively. The enrichment factors and recoveries ranged from 24 to 293 and 76–116%, respectively. The proposed method could be used simple, cheap, fast, and environmentally friendly alternative for analysis of organochlorine pesticides from environmental water and other similar matrices.

Rapid and efficient determination of zinc in water samples by graphite furnace atomic absorption spectrometry after homogeneous liquid-liquid microextraction via flotation assistance

ABSTRACT. A new application of homogeneous liquid–liquid microextraction via flotation assistance (HLLME-FA) has been developed for the determination of Zn(II) in the water samples by using graphite furnace atomic absorption spectrometry (GFAAS). 1-(2-Pyridylazo)-2-naphthol (PAN) was used as a chelating reagent. In this work, low density organic solvent was used as an extraction solvent and no centrifugation was required in this method. A special extraction cell was designed to facilitate collection of the low density extraction solvent. The predominant parameters influencing the HLLME-FA procedure, such as solution pH, concentration of PAN, extraction and homogeneous solvent types and volumes, ionic strength, and extraction time have been optimized. Applying all the optimum conditions in the process, the detection limit of 0.1 μg/L, linear range of 0.5–200 μg/L, and the precision (RSD%, n = 10) of 5.7% were obtained for zinc. The proposed procedure showed satisfactory results for the analysis of tap water, well water and sea water.
 
 KEY WORDS: Homogeneous liquid-liquid microextraction, Flotation assistance, Zinc, Graphite furnace atomic absorption spectrometry, Water samples
 Bull. Chem. Soc. Ethiop. 2022, 36(1), 1-11. 
 DOI: https://dx.doi.org/10.4314/bcse.v36i1.1

A density-tunable liquid-phase microextraction system based on deep eutectic solvents for the determination of polycyclic aromatic hydrocarbons in tea, medicinal herbs and liquid foods

A novel density-tunable liquid-phase microextraction (DT-LPME) system was developed with high-density deep eutectic solvents (DESs) as extractant and low-density organic solvents as emulsifier and density regulator. DES-rich phase was induced to form in the bottom or in the top by adjusting the emulsifier amount. This system was used to directly extract polycyclic aromatic hydrocarbons (PAHs) from liquid and solid foods, and the obtained DES-rich phase was easy to be collected for quantification. The method (LPME with HPLC-fluorescence detector) has linearity (R2 > 0.9974), detection limits of 0.6–4.2 ng L-1 for liquid foods and 0.05–0.35 ng g−1 for solid foods, recoveries of 86.2–114.9%, and intra-day/inter-day RSDs below 6.6%. The method was applied to detect PAHs in real samples, and the PAHs residue was found in honey and five solid foods. The DT-LPME method is simple, fast, green and suitable for direct extraction of analytes from both liquid and solid samples.

Homogeneous liquid-liquid microextraction via flotation assistance for determination of trace amounts of manganese prior to inductively coupled plasma-mass spectrometry

In the present study, homogeneous liquid-liquid microextraction via flotation assistance method is described for preconcentration of trace amounts of Mn(II). 1-(2-pyridylazo)-2-naphthol (PAN) is used as a ligand. The enriched analyte in the floated organic phase has been determined by inductively coupled plasma-mass spectrometry (ICP-MS). In this work, low density organic solvent is used and there is no need of centrifugation. Several factors influencing the microextraction efficiency, such as pH, the amount of chelating agent, nature and volume of extraction and homogeneous solvents have been investigated and optimized. Under the optimum conditions, the linear dynamic range is 1.0-500.0 ng L-1 with a correlation coefficient of 0.9998 and the detection limit of 0.1 ng L-1. The proposed method has been successfully applied for separation and determination of manganese in different water samples.

A Novel Method of Homogeneous Liquid–Liquid Microextraction via Flotation Assistance Coupled to Liquid Chromatography for the Determination of Trace Imidacloprid in Water Samples

This paper describes a novel method for the sensitive determination of imidacloprid using homogeneous liquid−liquid microextraction via flotation assistance (HLLME-FA) in water samples. After the extraction procedure, low density organic solvent was separated by air flotation. Various parameters affecting the extraction efficiencies such as the types of extraction and homogeneous solvents, the volumes of extraction and homogeneous solvents, extraction time and ionic strength were studied. Under the optimized conditions, the detection limit of imidacloprid was 0.02 µg/L. The experimental results indicated that there was good linearity (r2 = 0.9995) over the range of 0.25–500 µg/L. The relative standard deviation (n = 3) at the concentration level of 1.0 µg/L of imidacloprid in sea, well and river water samples was 11.1%. The proposed method has been successfully applied to the determination of imidacloprid in real water samples.

An innovative continuous sample drop flow microextraction for GC–MS determination of pesticides in grape juice and water samples

In this work, for the first time, low-density organic solvents were employed in continuous sample drop flow microextraction (CSDF-ME) by changing the design of extraction vessel. To examine the effectiveness of the modified extraction method, different organophosphorus pesticides (OPPs) were extracted using proposed method followed by detection by gas chromatography–mass spectrometry (GC–MS). In fact, unlike conventional CSDF approach, in this study, we applied halogen-free organic solvents that are lighter than water for analytes extractions. These solvents are not only less toxic but also more environmentally friendly compared to the halogenated solvents. A conical open-end vial fixed in a small container filled with double-distilled water was used as the extraction vessel. A small amount of extraction solvent was placed at the bottom of the vial and the sample solution was pumped into the extraction vessel through a needle located inside the vial using a peristaltic pump. The sample droplets were continuously passed through the extraction solvent (hexane; 13 μL) to extract the analytes. Once the extraction was completed, the extraction solvent left at the top of aqueous phase was collected and injected into the GC–MS for further analysis. Under optimized conditions, the repeatability of the proposed method was found to be in range of 3.9–5.8 % for samples with low concentration of 5.0 μg L−1. The LOD (limit of detection) and LOQ (limit of quantification) of the method were determined in the ranges of 0.02−0.30 and 0.07–1.0 μg L−1, respectively. The EF (enrichment factor) was found to be between 510 and 960 for 8.0 mL sample solutions. The proposed method allows an extraction recovery ranging between 25.5 % and 48.0 %.

Determination of benzo(a)pyrene in the exhaled breath condensate of cigarette smokers by microextraction and HPLC-UV

Development of an ultrasonication assisted microextraction based on low-density organic solvents coupled with HPLC-UV for extraction/determination of benzo(a)pyrene in exhaled breath condensate (EBC).

Modification of 3D polyacrylonitrile composite fiber for potential oil-water mixture separation

In this study, a two-dimensional (2D) microporous electrospun polyacrylonitrile (PAN) fiber mat was converted into a three-dimensional (3D) mesoporous fiber scaffold via a simple gas foaming technique with a solution of aqueous sodium borohydride (NaBH4). The 3D PAN fiber was coated with ZnO nano-flowers via a facile one-pot hydrothermal process. The 3D PAN/ZnO fibers were rendered modified into hydrophobic or oleophilic through subsequent treatment with dodecyltriethoxysilane (DTEOS). A modified 3D composite was successfully applied for the absorption of oils with a significant sorption capacity for a series of common oils and organic solvents. Interestingly, absorbed oil with in the 3D fiber composite was easily drained by simple mechanical squeezing. The modified hydrophobic 3D PAN/ZnO composite exhibited an excellent oil sorption capacity compared to the 2D PAN/ZnO composite. The oil sorption capacity of the 3D composite was 4 times higher for low density organic solvents and 2 times higher for high density, viscous oils compared to the 2D composite fiber. The effective oil sorption capacity of the 3D composite rendered it as a promising sorbent candidate for oil spill cleanup and oil-water purification.

3D Graphene-Oil Absorbent Resin Hybrid Gel as High Efficiency Oil Absorbent Material

A new type of high oil absorbent resin (OAR) was synthesized by emulsion polymerization with lauryl methacrylate (LMA) and butyl methacrylate (BMA) as soft monomers, and methyl methacrylate (MMA) as hard monomer. A graphene-oil absorbent resin hybrid aerogel (G-OAR aerogel) was therefore prepared through the hydrothermal reduction of graphene oxide colloidal solution and the oil absorbent resin emulsion. The self-assembly characteristics of graphene oxide in hydrothermal treatment resulted in the formation of 3D porous structure for G-OAR aerogel. The component, morphology and hydrophobicity of G-OAR aerogel were characterized by FTIR, XRD, SEM and contact angle, and its absorption capacities to different kinds of organic solvents and oils were also been investigated. The results indicate that the absorption capacities of G-OAR aerogel reach up to 40-50 g/g for low density organic solvents, like acetone, anhydrous alcohol, cyclohexane, toluene, ethyl acetate and diesel. The absorption capacities are 80-90 g/g for high density and weak polarity organic solvents, like phenixin and castor oil. The good oil absorption property makes it show high potential in the application of wastewater treatment and oil leakage.

Comparison of two microextraction methods based on solidification of floating organic droplet for the determination of multiclass analytes in river water samples by liquid chromatography tandem mass spectrometry using Central Composite Design

Two low density organic solvents based liquid–liquid microextraction methods, namely Vortex assisted liquid–liquid microextraction based on solidification of floating organic droplet (VALLME-SFO) and Dispersive liquid–liquid microextraction based on solidification of floating organic droplet(DLLME-SFO) have been compared for the determination of multiclass analytes (pesticides, plasticizers, pharmaceuticals and personal care products) in river water samples by using liquid chromatography tandem mass spectrometry (LC–MS/MS). The effect of various experimental parameters on the efficiency of the two methods and their optimum values were studied with the aid of Central Composite Design (CCD) and Response Surface Methodology(RSM). Under optimal conditions, VALLME-SFO was validated in terms of limit of detection, limit of quantification, dynamic linearity range, determination of coefficient, enrichment factor and extraction recovery for which the respective values were (0.011–0.219ngmL−1), (0.035–0.723ngmL−1), (0.050–0.500ngmL−1), (R2=0.992–0.999), (40–56), (80–106%). However, when the DLLME-SFO method was validated under optimal conditions, the range of values of limit of detection, limit of quantification, dynamic linearity range, determination of coefficient, enrichment factor and extraction recovery were (0.025–0.377ngmL−1), (0.083–1.256ngmL−1), (0.100–1.000ngmL−1), (R2=0.990–0.999), (35–49), (69–98%) respectively. Interday and intraday precisions were calculated as percent relative standard deviation (%RSD) and the values were ≤15% for VALLME-SFO and DLLME-SFO methods. Both methods were successfully applied for determining multiclass analytes in river water samples.

Tablet-effervescence-assisted dissolved carbon flotation for the extraction of four triazole fungicides in water by gas chromatography with mass spectrometry.

A pretreatment method named tablet-effervescence-assisted dissolved carbon flotation was introduced for the determination of four triazole fungicides in environmental water. In this method, the use of effervescent tablet composed of nontoxic sodium carbonate and sodium dihydrogen phosphate could generate CO2 in situ to assist the dispersion of extraction solvent and to accelerate mass transfer of target analytes. In addition, the simple phase separation simply based on the rising of low-density organic solvent from the aqueous phase was applied rather than the application of apparatus, which demonstrated the potential for on-site extraction in the field. The experimental variables, including the composition of effervescent tablets, amount of effervescent tablets, types and volume of extraction solvent, were investigated. Under the optimized conditions, the method showed good linearity for myclobutanil, tebuconazole, epoxiconazole, and difenoconazole in the range of 1-100 μg/L. The limits of detection and the limits of quantification were within the range of 0.15-0.26 and 0.49-0.86 μg/L, respectively. The obtained correlation coefficients varied from 0.997 to 0.999, and suitable enrichment factors were 422-589. The recoveries were 82.5-112.9% with relative standard deviations of 4.7-13.5%.

Development of a Microextraction Method Based on Dissolved Carbon Dioxide Flotation after Emulsification for the Determination of Triazole Pesticides Residues in Water Samples by Gas Chromatography-Mass Spectrometry.

A novel dissolved carbon dioxide flotation after emulsification microextraction (DCF-EME) method was proposed for the determination of four triazole pesticides in water samples coupled with gas chromatography-mass spectrometry (GC-MS) in a home-made glass round flask. The DCF-EME method is based on a rapid and simple phase separation of low-density organic solvent (toluene) from the aqueous phase via introducing a saturated NaHCO3 solution into the acidified sample (0.1 mol L-1 HCl); then analytes were extracted in toluene. Various parameters affecting the extraction process were optimized. Under the optimal conditions, the recoveries for four pesticides ranged from 82.8 to 121.2%. Meanwhile the limits of detection were at the range of 0.14 - 1.04 μg L-1, and the preconcentration factors were varied between 342 and 473 for different triazoles. The method is simple, fast and environmentally friendly, being successfully applied for the determination of triazole pesticides in water samples.

Low-density-solvent-based air-assisted liquid-liquid microextraction followed by gas chromatography with flame ionization detection for the determination of synthetic phenolic antioxidants in milk samples.

A simple and rapid sample pretreatment technique termed low-density-solvent-based air-assisted liquid-liquid microextraction has been developed for the extraction and preconcentration of three synthetic phenolic antioxidants including butylated hydroxyanisole, butylated hydroxytoluene, and tert-butyl hydroquinone from milk samples prior to their analysis by gas chromatography with flame ionization detection. In this method, initially trichloroacetic acid as a proteins precipitation agent is added to the sample, and then it is sonicated and centrifuged. The obtained aqueous phase is removed and the analytes extracted by the proposed method using a low-density organic solvent. Some important parameters such as type and volume of extraction solvent, ionic strength, pH, and centrifugation rate and time were studied. Under the optimum conditions, enrichment factors were obtained in the range of 501-614. LODs and quantification were between 0.76-1.16 and 2.66-3.96 ng mL(-1) , respectively. This method is rapid and requires less than 15 min for sample preparation.

Measurement of selected polychlorinated biphenyls (PCBs) in water via ultrasound assisted emulsification-microextraction (USAEME) using low-density organic solvents.

Despite bans and restrictions for their adverse health effects including endocrine disruption, due to their stability in the environment, polychlorinated biphenyls (PCBs) are still of concern for their residues in several matrices. This study employed low-density ultrasound-assisted emulsification-microextraction (USAEME) to measure selected PCBs (28, 52, 101, 118, 138, 153, and 180) in water samples for gas chromatography-mass spectrometry analysis. Among tested solvents (isooctane, chloroform, hexane, and cyclohexane), 200 μL isooctane resulted in the highest yield for a 10 mL sample. The optimized method was validated and yielded recoveries of 87.29-92.83% with the limit of detection and limit of quantification (LOQ) values 3-12 ng/L and 10-40 ng/L, respectively. Twelve tap water samples collected in September 2014 were screened using this simple, rapid, and validated method. PCB concentrations in two samples were above the LOQ values; one sample contained 1,380 ng/L of PCB 118, 530 ng/L of PCB 138, and 152 ng/L of PCB 153, and the other contained 444 ng/L of PCB 138. Despite the city water supply being clean and the municipality employing all available measures to ensure clean water supply, the general public must be made aware of the regular maintenance of local water pipelines and storage tanks for the prevention of PCB contamination.

Dissolved carbon dioxide flotation: An effective way for phase separation in emulsification microextraction method

Dissolved carbon dioxide flotation after emulsification microextraction (DCF-EME) technique coupled with gas chromatography-electron capture detection (GC-ECD) was introduced for preconcentration and determination of six organochlorine pesticides (OCPs) in seawater samples. DCF-EME method is based on the rapid and simple phase separation of low density organic solvent from the aqueous phase via introducing of a saturated NaHCO3 solution (9.6% w/v) into the acidified sample solution (0.1M of HCl) containing analytes. Thanks to the in situ generation of carbon dioxide (CO2) bobbles intensified by ultrasound radiation, the dispersed extraction solvent was collected to the surface of the aqueous sample and then was narrowed to the capillary part of a special home-made extraction cell for facile retrieving. Under the optimal conditions, the limits of detection were at the range of 2.6–9.2ngL−1 and preconcentration factors were varied between 271 and 307 for different OCPs. The applicability of the developed method was evaluated by the extraction and determination of the target analytes from Caspian seawater samples.

Extraction and Separation of Molybdenum by Using Homogeneous Liquid-Liquid Microextraction via Flotation Assistance

Homogeneous liquid-liquid microextraction via flotation assistance (HLLME-FA) was investigated for the extraction of molybdenum from the water samples. Alizarin Red S and cetyl trimethylammonium bromide (CTAB) were used as a complexing ligand and ion-pairing reagent, respectively. The enriched analyte in the floated organic phase was determined by electrothermal atomic absorption spectrometry (ETAAS). In this work, low density organic solvent was used and no centrifugation was required in this procedure. A special extraction cell was designed to facilitate the collection of the low-density extraction solvent. By using air flotation, the organic solvent was collected at the conical part of the designed cell. Under the optimum conditions, the method performance was studied in terms of linear dynamic range (0.5-200 µg L-1), linearity (r2 > 0.991), precision (repeatability < 10.0 %). Also, the limit of detection (LOD) of 0.1 µg L-1 was obtained for molybdenum. The proposed method has been successfully applied for the determination of the molybdenum in water samples.

Application of Ultrasound-Assisted Emulsification Microextraction Based on Applying Low Density Organic Solvents to the Extraction and Determination of Mononitrotoluenes in Water Samples

In this study, simple and efficient ultrasound-assisted emulsification microextraction (USAEME) based on applying low density organic solvents combined with gas chromatography-flame ionization detector (GC-FID) was developed for the preconcentration and determination of mononitrotoluenes (MNTs) in water samples. In this method, the fine droplets of toluene were formed and dispersed in the sample with the help of ultrasonic waves which accelerated the formation of the fine cloudy solution without using disperser solvents. Several factors influencing the extraction efficiency such as the nature and volume of organic solvent, extraction temperature, ionic strength and centrifugation time were investigated and optimized. Using optimum extraction conditions, dynamic linear ranges of 0.5-500 μg L-1, and limit of detections (LOD) of 0.3 μg L-1 were obtained for o-nitrotoluene, m-nitrotoluene and p-nitrotoluene. Finally, the method was successfully applied to the extraction and determination of MNTs in the water samples in the range of micrograms per liter with relative standard deviations (RSD) < 12%.

Rapid pretreatment and determination of bisphenol A in water samples based on vortex-assisted liquid-liquid microextraction followed by high-performance liquid chromatography with fluorescence detection.

A method for the rapid pretreatment and determination of bisphenol A in water samples based on vortex-assisted liquid-liquid microextraction followed by high-performance liquid chromatography with fluorescence detection was proposed in this paper. A simple apparatus consisting of a test tube and a cut-glass dropper was designed and applied to collect the floating extraction drop in liquid-liquid microextraction when low-density organic solvent was used as the extraction solvent. Solidification and melting steps that were tedious but necessary once the low-density organic solvent used as extraction solvent could be avoided by using this apparatus. Bisphenol A was selected as model pollutant and vortex-assisted liquid-liquid microextraction was employed to investigate the usefulness of the apparatus. High-performance liquid chromatography with fluorescence detection was selected as the analytical tool for the detection of bisphenol A. The linear dynamic range was from 0.10 to 100 μg/L for bisphenol A, with good squared regression coefficient (r(2) = 0.9990). The relative standard deviation (n = 7) was 4.7% and the limit of detection was 0.02 μg/L. The proposed method had been applied to the determination of bisphenol A in natural water samples and was shown to be economical, fast, and convenient.

Microfunnel-supported liquid-phase microextraction: Application to extraction and determination of Irgarol 1051 and diuron in the Persian Gulf seawater samples

In the present work, microfunnel-supported liquid-phase microextraction method (MF-LPME) based on applying low density organic solvent was developed for the determination of antifoulings (Irgarol 1051, diuron and 3,4-dichloroaniline) from seawater samples. In this method, home-designed MF device was used for facile loading and retrieving of organic solvent during the extraction procedure. The extraction was carried out with introduction of 400μL of toluene via syringe into the MF device placed on the surface of sample solution (300mL) containing analytes. After the extraction, extractant layer was narrowed into the capillary part of MF by pushing the device inside the sample and withdrawn by using a syringe to evaporate by nitrogen purging. The residual redissolved into 50μL methanol, diluted to 100μL with deionized water and injected into the high performance liquid chromatography with UV detection (HPLC–UV). Several factors influencing the extraction such as the type and volume of extraction solvent, sample pH, extraction time and ionic strength were investigated and optimized. Under the optimized conditions, the limits of detection in seawater were 1.4, 4.8 and 1.0ngL−1 for 3,4-dichloroaniline (DCA), diuron and Irgarol 1051, respectively. Enrichment factors were obtained 333, 150 and 373 for DCA, diuron and Irgarol 1051, respectively. The precision of the technique was evaluated in terms of repeatability which was less than 12.0% (n=5). The applicability of the proposed method was evaluated by the extraction and determination of antifoulings from seawater samples collected from harbors of Bushehr located in northern Persian Gulf coast.

Desirability function approach for the optimization of an in-syringe ultrasound-assisted emulsification-microextraction method for the simultaneous determination of amlodipine and nifedipine in plasma samples

In the present study, an in-syringe ultrasound-assisted emulsification-microextraction using a low-density organic solvent was developed for simultaneous extraction and pre-concentration of amlodipine besylate and nifedipine from plasma samples. The extracts were analyzed by high-performance liquid chromatography with UV detection. Central composite design combined with desirability function was applied to find out the optimal experimental conditions providing the highest global extraction efficiency. The optimal conditions identified were volume of the extracting solvent 45 μL, ionic strength 18.95% w/v, sonication time 2.58 min, and centrifugation time 3 min. Under the optimal conditions, the proposed method was evaluated, and applied to the analysis of amlodipine besylate and nifedipine in plasma samples. The validation results of the method indicated a wide linear range (2-1200 ng/mL) with a good linearity (r(2) >0.9991) and low detection limits (0.17 ng/mL for amlodipine besylate and 0.15 ng/mL for nifedipine) with RSD less than 5.2% for both components, both in intra- and inter-day precision studies. The applicability of the proposed in-syringe ultrasound-assisted emulsification-microextraction coupled to high-performance liquid chromatography with UV detection method was demonstrated by analyzing the drugs in spiked plasma samples.