Low-density Extraction Solvent Research Articles

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

Development of an in–syringe gas–assisted density tunable solidification of floating organic droplet–based dispersive liquid phase microextraction method coupled with HPLC–MS/MS for monitoring amikacin in biological fluids

A new sample preparation method named in–syringe gas–assisted density tunable dispersive liquid phase microextraction based on solidification of floating organic droplet has been introduced. This method was coupled with high–performance liquid chromatography–tandem mass spectrometry and used for the extraction and quantification of amikacin in plasma and exhaled breath condensate (EBC) samples of the patients receiving amikacin. In the proposed approach, an inert gas is bubbled into a syringe barrel containing aqueous solution of the analyte and a mixture of low density extraction solvent and volatile density modifier. Consequently, the density modifier is evaporated and the analyte is migrated into the released extractant droplets. Basic parameters affecting efficiency of the developed method were optimized. Under optimum conditions, the method limits of detection were 0.06 and 0.29 ng/mL in EBC and plasma, respectively. The extraction recoveries were 90% and 87% in EBC and plasma, respectively. Also, the obtained relative standard deviations were below 9.5% and 9.8% for EBC and plasma, respectively. Considering these results, the developed method provides a quick and efficient way to determine amikacin in patients’ biological fluids and can be used widely in drug monitoring and clinical studies.

Extraction and preconcentration of Bisphenol A and 4-Nonylphenol in aqueous solutions using microfunnel supported liquid-phase microextraction prior to high performance liquid chromatography

In this study, liquid-phase microextraction using low-density extraction solvents with microfunnel was applied for the extraction and preconcentration of Bisphenol A and 4-Nonylphenol in aqueous samples. The goal of the present method is to develop a special device that allows organic solvent remain on the surface of aqueous phase as a thin layer during the extraction time. At the end of extraction period, organic phase containing the extracted analytes was collected easily and analyzed by HPLC–FLD. Toluene used as extraction solvent and some of experimental parameters were optimized by L16 Taguchi experimental design. According to the results, the volume of extraction solvent as well as ionic strength showed significant effect on the extraction recovery. Under the optimum conditions (sample volume: 320 mL; pH 8.0; ionic strength: 10% (w/v) NaCl, extraction time: 90 min and extractant: 600 μL toluene), limit of detection, limit of quantification and dynamic linear range of the proposed method for Bisphenol A were calculated as 0.05, 0.2 and 0.2–62.5 μg L−1, and for Nonylphenol were obtained as 3.1, 6.2 and 6.2–125 μg L−1, respectively.

A novel air-assisted liquid-liquid microextraction based on in-situ phase separation for the HPLC determination of bisphenols migration from disposable lunch boxes to contacting water

In this study, a novel air-assisted liquid-liquid microextraction (AALLME) method was developed for the HPLC determination of bisphenols migration from disposable plastic lunch box to contacting water. The AALLME was carried out in commercially-available medical plastic syringes with low-density extraction solvent (n-octanol), and the reaction of NaHCO3 and HCl was introduced to simultaneously induce the in-situ phase separation and salt effect. After the AALLME processes, the upper organic phase was pushed into the end of syringes (narrow tube) by moving the piston so that it could be readily collected for the HPLC analysis. The factors including the type and volume of extraction solvent, NaHCO3 addition and extraction cycles were optimized. Under the optimal conditions, the limits of detection (LODs) for target bisphenols were evaluated to be 0.2–0.7 μg L−1, and good linearities with correlation coefficients higher than 0.9955 were obtained. The recoveries for target bisphenols ranged from 80% to 106%, with the relative standard deviations (RSDs) of 4.4–14.1%. The proposed method was successfully applied to investigate the migration of bisphenols from the disposable plastic lunch boxes to the contacting water, revealing that compared to the conventional water-bath heating, the microwave heating could induce the significant migration of bisphenols in a much shorter time.

Large volume of water samples introduced in dispersive liquid-liquid microextraction for the determination of 15 triazole fungicides by gas chromatography-tandem mass spectrometry.

A novel method of large volume of water samples directly introduced in dispersive liquid-liquid microextraction was developed, which is based on ultrasound/manual shaking-synergy-assisted emulsification and self-generating carbon dioxide gas (CO2) breaking down the emulsion for the determination of 15 triazole fungicides by gas chromatography-tandem mass spectrometry. This technique makes low-density extraction solvent toluene (180μL) dissolve in 200mL of samples containing 0.05molL(-1) of HCl and 5% of NaCl (w/v) to form a well emulsion by synergy of ultrasound and manual shaking, and injects NaHCO3 solution (1.0molL(-1)) to generate CO2 achieving phase separation with the assistance of ultrasound. The entire process is accomplished within 8min. The injection of NaHCO3 to generate CO2 achieves phase separation that breaks through the centrifugation limited large volume aqueous samples. In addition, the device could be easily cleaned, and this kind of vessel could be reconfigured for any volume of samples. Under optimal conditions, the low limits of detection ranging from 0.7 to 51.7ngL(-1), wide linearity, and enrichment factors obtained were in the range 924-3669 for different triazole fungicides. Southern end of the Beijing-Hangzhou Grand Canal water (Hangzhou, China) was used to verify the applicability of the developed method. Graphical Abstract Flow chart of ultrasound/manual shaking-synergy-assisted emulsification and self-generating carbon dioxide gas breaking down the emulsion.

Ion-Pair-Based Air-Assisted Liquid–Liquid Microextraction for the Extraction and Preconcentration of Phthalic Acids from Aqueous Samples

In the present study, a rapid, simple, and highly efficient sample preparation method based on ion-pair air-assisted liquid–liquid microextraction using a low-density extraction solvent followed by high performance liquid chromatography–diode array detection has been developed for the extraction, preconcentration, and determination of three phthalic acids (phthalic acid, iso-phthalic acid, and terephthalic acid) in aqueous samples. In this method, a mixture of tri-butyl amine (as an ion-pair reagent) and toluene (as an extraction solvent) is transferred into an aqueous sample solution. Fine organic solvent droplets are formed by aspirating and dispersing of the mixture via syringe needle. After that, the formed ion-pairs are extracted into toluene, and after centrifuging, the obtained collected phase is transferred into a microtube and is evaporated to dryness under a stream of nitrogen at room temperature. The residue is re-dissolved in mobile phase and injected into the separation system for analysis. Under the optimum extraction conditions, the method showed low limits of detection and quantification between 0.09–0.24 and 0.29–0.78 ng mL−1, respectively. Extraction recoveries and enrichment factors were from 88 to 98 % and 443 to 491, respectively. Relative standard deviations for the extraction of 5 ng mL−1 of each analyte were less than 8.4 % for intra-day (n = 6) and inter-days (n = 5) precisions. Finally, different aqueous samples were successfully analyzed using the proposed method, and the target analytes were determined in some of them at ng mL−1 level.

Development of Flotation-assisted Homogeneous Liquid–Liquid Microextraction to Determine Organochlorine Pesticides in Soil by GC-MS

Abstract This work describes optimal flotation-assisted homogeneous liquid–liquid microextraction with a special homemade extraction cell that was designed to collect the low-density extraction solvent without centrifugation for the extraction of heptachlor, aldrin, trans-chlordane, cis-chlordane, and op-DDD in soil samples. The extraction solvent was transferred to GC-MS for analysis in the selected ion-monitoring mode. To obtain the optimum conditions for extraction, a rotatable face-centered central composite design consisting of three factors at three levels was used. Under optimum conditions, the method performance was studied in term of the linear dynamic range (LDR from 0–500 µg kg−1 soil), linearity (R2 > 0.9989), and precision (in the range of 0.036–0.062).

Development of a low-density-solvent dispersive liquid-liquid microextraction with gas chromatography and mass spectrometry method for the quantitation of tetrabromobisphenol-A from dust.

The development of an alternative dispersive liquid-liquid microextraction protocol utilizing a low-density extraction solvent, toluene, is described here for the extraction of the brominated flame retardant, tetrabromobisphenol-A, from dust prior to selected ion monitoring analysis by gas chromatography with mass spectrometry. Method parameters of dispersive solvent type and extraction solvent type were optimized. Excellent recovery (88.9%; n = 5 spike replicates) with good precision was achieved in a spike and recovery study. This developed method was utilized to survey tetrabromobisphenol-A concentrations in dust sampled from a local electronics recycling facility from the ambient environment and 20 computer towers undergoing recycling. Concentrations of tetrabromobisphenol-A from dust in computer towers ranged from not detected (n = 2) up to 64 μg/g with a mean value of 11 μg/g and median of 4.1 μg/g tetrabromobisphenol-A. A composite sample of dust collected from the ambient indoor environment was analyzed with a resulting concentration of 36 μg/g. This is the first application of this novel green method for pre-concentrating flame retardants from dust and the first report of tetrabromobisphenol-A concentrations at a U.S.-based electronics recycling facility.

Determination of uranium in water samples using homogeneous liquid–liquid microextraction via flotation assistance and inductively coupled plasma-optical emission spectrometry

A new method was developed for the preconcentration and determination of uranium in the water samples using homogeneous liquid–liquid microextraction via flotation assistance and inductively coupled plasma-optical emission spectrometry. A special extraction cell was designed to facilitate collection of the low-density extraction solvent by using air flotation for extraction of uranium. Under the optimized condition a linear response was obtained over the range of 1.25–100 µg L−1 for uranium. Limit of detection and relative standard deviation of the proposed HLLME-FA method were obtained 0.4 µg L−1 and 6.6 % for uranium, respectively.

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.

Negative corona discharge-ion mobility spectrometry as a detection system for low density extraction solvent-based dispersive liquid–liquid microextraction

This paper deals with a method based on negative corona discharge ionization ion mobility spectrometry (NCD-IMS) for the analysis of ethion (as an organophosphorus pesticide). The negative ions such as O2− and NOx− were eliminated from the background spectrum to increase the instrument sensitivity. The method was used to specify the sample extracted via dispersive liquid–liquid microextraction (DLLME) based on low density extraction solvent. The ion mobility spectrum of ethion in the negative mode and the reduced mobility value for its ion peak are firstly reported and compared with those of the positive mode. In order to combine the low density solvent DLLME directly with NCD-IMS, cyclohexane was selected as the extraction solvent, helping us to have a direct injection up to 20µL solution, without any signal interference. The method was exhaustively validated in terms of sensitivity, enrichment factor, relative recovery, and repeatability. The linear dynamic range of 0.2–100.0µgL−1, detection limit of 0.075µgL−1, and the relative standard deviation (RSD) of about 5% were obtained for the analysis of ethion through this method. The average recoveries were calculated about 68% and 92% for the grape juice and underground water, respectively. Finally, some real samples were analyzed and the feasibility of the proposed method was successfully verified by the efficient extraction of the analyte using DLLME before the analysis by NCD-IMS.

Extraction and determination of sulfonylurea herbicides in water and soil samples by using ultrasound-assisted surfactant-enhanced emulsification microextraction and analysis by high-performance liquid chromatography

An ultrasound-assisted surfactant-enhanced emulsification microextraction (UASEME) with low-density extraction solvents was developed for the extraction of sulfonylurea herbicides from water and soil samples prior to high-performance liquid chromatography coupled with ultraviolet detection (HPLC–UV). In this technique, a surfactant was used as emulsifier which could enhance the dispersion of water-immiscible extraction solvent into aqueous phase and was favorable for the mass-transfer of the analytes from aqueous phase to organic phase. The target analytes were extracted into an extraction phase (Aliquat-336 in1-octanol) and dispersed in an aqueous solution. After extraction and phase separation, the organic solvent on top of the solution was withdrawn into a syringe and 20µL of it was injected into a HPLC instrument for analysis. Influential factors in extraction were investigated and optimized. Under optimum experimental conditions, calibration curve was linear in the concentration range from 1 to 100µg/L, with coefficients of estimation (R2 values) varying from 0.9928 to 0.9952, and satisfactory repeatabilities (4.7<RSDs%<6.1) were attained. High preconcentration factors were achieved ranging from 103 to 153. Applicability of the method to the extraction of sulfonylurea herbicides from different types of complicated matrices, such as water and soil samples, was studied. The obtained results indicated that the proposed method is efficient, fast and inexpensive for extraction and determination of sulfonylurea herbicides in environmental aqueous and soil samples.

Retrieval of the Extraction Solvent by Magnetic Particles for Dispersive Liquid–Liquid Microextraction of UV Filters

A simple dispersive liquid–liquid microextraction (DLLME) method, based on retrieval of the extraction solvent by magnetic particles and followed by HPLC–UV analysis, was proposed for the determination of UV filters in environmental water samples. The new method uses vortex agitation in the DLLME process to achieve rapid equilibrium. Another feature of the proposed method is that the retrieval of the extraction solvent is accomplished by functionalized magnetic particles rather than by special designed vessels or refrigeration and thawing process associated with DLLME when low-density extraction solvent was used. The parameters that may influence the extraction, including vortex time, volume of extraction solvent, weight of the magnetic particles, volume of desorption solvent, pH, and ionic concentration of the sample solution, were investigated in detail. Under the optimized conditions, the limits of detection for the target UV filters were in range of 0.7–12.3 ng mL−1. The results also demonstrated good linearity and precision, with the regression coefficients above 0.9989 and the RSDs below 4.4%, respectively.

Alternative Green Preconcentration Approach Based on Ultrasound-Assisted Surfactant-Enhanced Emulsification Microextraction and HPLC for Determination of Benzimidazole Anthelmintics in Milk Formulae

An alternative green microextraction method based on ultrasound-assisted surfactant-enhanced emulsification microextraction (UASEME) using a low-density extraction solvent coupled with HPLC has been developed for preconcentration and determination of six benzimidazole anthelmintics, namely, oxfendazole, albendazole, mebendazole, flubendazole, fenbendazole, and niclosamide. The separation was achieved within 12 min, using an Inertsil® C18 column (4.6 × 150 mm, 5.0 µm), with a gradient mobile phase of acetonitrile and 0.1 % (v/v) formic acid. Under the optimum UASEME conditions using Tergitol® TMN-6 and 1-octanol as emulsifier and extraction solvent, respectively, linearity was in the range of 0.5–5,000 μg L−1 with the coefficients of determination (R 2) ranging from 0.9959 to 0.9999. Enrichment factors were obtained up to 89, corresponding to limits of detection ranging from 0.50 to 6.00 µg L−1. Intra-day (n = 8) and inter-day (n = 3 × 3) precisions were obtained with relative standard deviations for retention time and peak area of lower than 2 and 15 %, respectively. The proposed method was successfully applied to determine the target benzimidazoles in milk formulae.

HOMOGENEOUS LIQUID–LIQUID MICROEXTRACTION VIA FLOTATION ASSISTANCE FOLLOWED BY HIGH-PERFORMANCE LIQUID CHROMATOGRAPHY AS AN EFFICIENT AND SENSITIVE TECHNIQUE FOR THE DETERMINATION OF ABAMECTIN IN AQUATIC SAMPLES

Homogeneous liquid–liquid microextraction via flotation assistance (HLLME-FA) and high-performance liquid chromatography-UV detection was presented for the extraction and determination of abamectin in aquatic samples. Toluene at microliter volume level and acetone were used as extraction and homogeneous solvents, respectively. In this research, a special extraction cell was designed to facilitate collection of the low-density extraction solvent. No centrifugation was required in this procedure. The water sample solution was added into the extraction cell, which contained an appropriate mixture of extraction and homogeneous solvents. Using air flotation, extraction solvent was collected at the conical part of the designed cell. The effects of different variables on the efficiency of the extraction such as kind and the volume of extraction and homogeneous solvents, ionic strength, and extraction time were studied and optimized. Under the optimum conditions, the calibration graphs were linear in the range of 2.0–500 µ g L−1 for B1a and 4.0–500 µ g L−1 for B1b with detection limits of 0.5 µ g L−1 for B1a and 1.7 µ g L−1 for B1b. HLLME-FA is a fast, simple, and efficient method for the determination of abamectin in aquatic samples.

PH‐assisted homogeneous liquid–liquid microextraction using dialkylphosphoric acid as an extraction solvent for the determination of chlorophenols in water samples

In this study, a new pH-assisted homogeneous liquid-liquid microextraction combined with HPLC with UV detection was developed for the determination of chlorophenols in water samples. In this approach, bis(2-ethylhexyl) phosphate was used for the first time as the low-density extraction solvent. In particular, 60 μL of bis(2-ethylhexyl) phosphate was injected into the sample solution (5 mL) and dissolved completely in the sample solution while the pH was increased to 9. Afterwards, the pH of the sample solution was lowered to 1, and a cloudy solution was formed. At this stage, hydrophobic interactions between the analytes and the long double hydrocarbon chains of extraction solvent were expected to be the main forces driving extraction. A series of parameters that influence extraction were investigated systematically. Under the optimized conditions, the LODs and LOQs for the chlorophenols were 1.4-2.7 and 4.7-9.1 ng/mL, respectively. RSDs based on five replicate extraction of 100 ng/mL of each chlorophenols were <4.7% for intraday and 7.4% for interday precision. This method has been also successfully applied to analyze real water samples at two different spiked concentrations, and satisfactory recoveries were achieved.

Ultrasound-assisted surfactant-enhanced emulsification microextraction for the determination of carbamates in wines by ultra-high performance liquid chromatography–tandem mass spectrometry

A new sensitive multiresidue method based on ultra-high performance liquid chromatography–tandem mass spectrometry (UHPLC–MS/MS) has been developed for the detection, confirmation and quantification of twenty five carbamates in wine samples. The separation was achieved in 5.5min, using a Zorbax Eclipse plus RRHD C18 column (50mm×2.1mm, 1.8μm), with a mobile phase of water and methanol, both of them with 0.01% formic acid. The analytes were detected in positive mode with multiple reaction monitoring mode. Ultrasound-assisted surfactant-enhanced emulsification microextraction (UASEME), using a low-density extraction solvent has been optimized for the satisfactory extraction of carbamates and clean-up of extracts. The matrix effect was studied, showing that the proposed procedure provides very clean extracts. Under optimum conditions, recoveries for fortified wine samples ranged from 74 to 102%, with relative standard deviations lower than 6%. Limits of quantification ranged from 0.15 to 0.92μgl−1, showing the high sensitivity of this fast and simple method and its compliance with current requirements.

Acid‐induced homogenous liquid‐phase microextraction: Application of medium‐chain carboxylic acid as extraction phase

In this research, a novel homogeneous liquid-phase microextraction method was successfully developed based on applying octanoic acid as low-density extraction solvent. The method was applied for extraction and determination of chlorophenols (CPs) as model compounds. Twelve milliliter of the sample solution was poured into a home-designed glass vial. Sixty microliter of octanoic acid was solved in water sample by adjusting pH and ionic strength. By rapid addition of 75 μL of concentrated HCl (6 M), a cloudy solution was obtained. Phase separation occurred at 5000 rpm for 5 min. After that, 20 μL of the collected phase (approximately 26 μL) was injected into the HPLC-UV instrument for analysis. The effect of some parameters such as the volume of concentrated HCl (phase separation reagent), ionic strength, extraction time, centrifugation time, and the volume of extracting phase on the extraction efficiency of the CPs were investigated and optimized. The preconcentration factors in a range of 159-218 were obtained under the optimal conditions. The linear range, detection limits (S/N = 3), and precision (n = 3) were 1- 200, 0.3-0.5 μg/L, and 4.6-5.1%, respectively. Tap water, seawater, and river water samples were successfully analyzed for the existence of CPs using the proposed method and satisfactory results were obtained.

Determination of bisphenol-A, 2,4-dichlorophenol, bisphenol-AF and tetrabromobisphenol-A in liquid foods and their packaging materials by vortex-assisted supramolecular solvent microextraction/high-performance liquid chromatography

A new and fast microextraction technique termed vortex-assisted supramolecular solvent microextraction (VASUSME) has been developed. The method was based on the microextraction of endocrine disrupting compounds (EDCs), including bisphenol-A (BPA), 2,4-dichlorophenol (2,4-DCP), bisphenol-AF (BPAF) and tetrabromobisphenol-A (TBBPA) in 10 mL sample with 500 μL of a supramolecular solvent (SUPRASs), and then detection by high-performance liquid chromatography (HPLC). In the VASUSME procedure, dispersion of microvolumes of a low density extraction solvent into the aqueous sample is achieved by vortex mixing, a mild emulsification procedure. Under the optimum conditions, the repeatability of the proposed method was found to be good. The relative standard deviations (RSD, n = 5) were 3.98–5.64%. The limits of detection (LOD) were in the range of 0.14–0.32 ng mL−1 and the limits of quantification (LOQ) were in the range of 0.41–1.02 ng mL−1. All correlation coefficients of the calibration curves were higher than 0.998. Recoveries of the EDCs spiked into samples of liquid foods and their packaging materials were in the range of 91% to 105.1%. The VASSUSME method was successfully applied to the analysis of BPA, 2,4-DCP, BPAF and TBBPA in samples of liquid foods and their packaging materials. Moreover, the method is simple, sensitive and environmentally-friendly and consumes much less solvent than traditional methods.

Determination of polycyclic aromatic hydrocarbons in soil samples using flotation-assisted homogeneous liquid–liquid microextraction

In this study, flotation-assisted homogeneous liquid–liquid microextraction (FA-HLLME) was developed as a fast, simple, and efficient method for extraction of four polycyclic aromatic hydrocarbons (PAHs) in soil samples followed by gas chromatography-flame ionization detector (GC-FID) analysis. A special home-made extraction cell was designed to facilitate collection of the low-density extraction solvent without a need for centrifugation. In this method, PAHs were extracted from soil samples into methanol and water (1:1, v/v) using ultrasound in two steps followed by filtration as a clean-up step. The filtrate was added into the home-made extraction cell contained mixture of 1.0mL methanol (homogenous solvent) and 150.0μL toluene (extraction solvent). Using N2 flotation, the dispersed extraction solvent was transferred to the surface of the mixture and was collected by means of a micro-syringe. Then, 2μL of the collected organic solvent was injected into the GC-FID for subsequent analysis. Under optimal conditions, linearity of the method was in the range of 40–1000μgkg−1 soil (dry weight). The relative standard deviations in real samples varied from 5.9 to 15.2% (n=4). The proposed method was successfully applied to analyze the target PAHs in soil samples, and satisfactory results were obtained.