Ultrasound-assisted Back-extraction Research Articles

An Ultraperformance Liquid Chromatography Tandem-Mass Spectrometry Method for Determination of Multiclass Pharmaceuticals in Water Sample by Dispersive Liquid-Liquid Microextraction Combined with Ultrasound Assisted Reverse Extraction from Solidified Floating Organic Droplets.

A novel, simple, and reliable ultraperformance liquid chromatography tandem-mass spectrometry (UPLC–MS/MS ) assay based on dispersive liquid–liquid microextraction followed by ultrasound-assisted reverse extraction from solidified floating organic droplets was established for determination of multiclass pharmaceuticals in the water sample. Six commonly used drugs of various therapeutic classes: ibuprofen, ketorolac, lamotrigine, propranolol, pantoprazole, and losartan were extracted from water samples by using 50 μL 1-undecanol as extracting solvent and 400 μL acetonitrile as dispersive solvent. After collecting the floating organic droplets by cold centrifugation, an ultrasound-assisted back extraction procedure was performed to make the sample compatible for UPLC–MS/MS analysis. Acquity BEH C18 column (2.1 × 100; 1.7 μm) was used for separation of target analytes that were eluted by a gradient mobile phase composition of 15 mM ammonium acetate and acetonitrile at a flow rate of 0.25 mL/min. The sample ionization was performed by using electrospray ionization in positive mode, and multiple reaction monitoring was used for quantification of target analytes. After optimizing the assay conditions, all calibration curves were found to be linear with limit of detection and limit of quantification were ranged in between 0.06–0.15 and 0.16–0.41 ng/mL, respectively. The enrichment factor was found to be 172–192-fold and the relative recovery was ranged between 93.1 and 109.4% between target analytes. These satisfactory results confirmed that the proposed method is specific and reliable for application of trace analysis of target analytes in waste water samples.

Cloud point extraction coupled with ultrasound-assisted back-extraction for determination of trace legacy and emerging brominated flame retardants in water using isotopic dilution high-performance liquid chromatography-atmospheric pressure chemical ionization-tandem mass spectrometry

Isotopic dilution high-performance liquid chromatography-atmospheric pressure chemical ionization-tandem mass spectrometry method was developed for determination of seven legacy and emerging brominated flame retardants (BFRs) in water using cloud point extraction coupled with ultrasound-assisted back-extraction. The effects of different experimental conditions on the recovery and matrix effect during cloud point extraction were investigated. Under the optimum conditions (sample volume: 40 mL; Triton X-114 concentration: 1.0 g L−1; equilibration temperature: 40 °C; equilibration time: 10 min; NH4OAc concentration: 0.5 M), the absolute recoveries obtained by cloud point extraction for the seven BFRs ranged from 64.0% to 108.8%, with matrix effect factors ranging between 0.70 and 1.07. Ultrasound-assisted back-extraction combined with isotope dilution mass spectrometry was utilized to enhance the enrichment factor and improve the repeatability. Under the optimized conditions, method limits of detection for BFRs ranged from 0.3 to 3.0 ng L−1. The average recoveries were in the range of 92.9–113.6% and 86.0–99.3% for spiked water samples at 10 and 100 ng L−1 of each BFR. The intra- and inter-day relative standard deviations (n = 6) were less than 5.4% and 8.0%, respectively. The results demonstrated that the proposed method was highly sensitive, efficient and reliable for the determination of trace legacy and emerging BFRs in water samples.

UPLC-MS/MS determination of suvorexant in urine by a simplified dispersive liquid-liquid micro-extraction followed by ultrasound assisted back extraction from solidified floating organic droplets

Suvorexant is a novel sedative/hypnotic drug approved for treatment of insomnia. It has significant forensic importance due to its hypnotic and depressant effects on central nervous system. In this study, a highly sensitive UPLC-MS/MS assay was developed and validated for the determination of suvorexant in urine sample. A simplified dispersive liquid-liquid microextraction followed by ultrasound assisted back extraction from solidified floating organic droplets was employed for sample preparation. The 20 μL of 1-undecanol and 200 μL of acetonitrile were used as extraction solvent and dispersive solvent, respectively. An ultrasound assisted back extraction step was employed to enable the cleanup procedure compatible with mass spectrometric detection. Acquity CSH™C18 column with mobile phase composition of 15 mM ammonium acetate: acetonitrile: formic acid (15:85:0.1%; v/v/v) were used for chromatographic separation. The multiple reaction monitoring transition of 451.12 →104.01 and 451.12→186.04 were used for identification and quantification of suvorexant, respectively, whereas 237.06→194.1 was used for IS in positive mode. The assay demonstrated good linearity in the range of 0.27–1000 ng mL−1 with limit of detection (LOD) and quantification (LOQ) of 0.10 and 0.27 ng mL-1, respectively. Assay validation was performed by following SWGTOX guidelines and all validation results were found to be within acceptable limits. This is the first report of dispersive liquid-liquid microextraction based on solidification of floating organic droplets employed to UPLC-MS/MS for application in biological fluids.

Cloud Point Pre-Concentration Coupled With Ultrasound-Assisted Back Extraction Of Permethrin And Alfa-Cypermethrin For GC-FID Determination In Waters And Foods

A new method of cloud point extraction coupled with ultrasound-assisted back extraction that is followed by GC-FID determination of permethrin and α-cypermethrin in waters, vegetables, and fruits was developed. The effect of several parameters on the extraction process, such as the concentration of Triton X-114, pH, incubation time, equilibration temperature and centrifuging parameters were studied and optimized. The complete extraction of pesticides with using 0.5 % solution of Triton X-114 at phase separation temperature of 40 °C is observed in the pH range from 2.0 to 9.0 when both analytes are present in the solution in electroneutral form. The surfactant-rich phases were formed by centrifuging solutions at 4000 rpm for 10 min. The method was validated and characterized by the following metrological parameters: for permethrin LOD (3σ) - 0.12 μg/ml, LOQ (10σ) - 0.38 μg/ml, working range 0.38 - 2.0 μg/ml; for α-cypermethrin LOD (3σ) - 0.04 μg/ml, LOQ (10σ) - 0.13 μg/ml, working range - 0.13 - 2.0 μg/ml. The procedure was used to determine permethrin and α-cypermethrin in potatoes, cabbage, pepper, table beets and apples after their treatment with commercial preparations of pesticides. The obtained results show that the sensitivity, metrological characteristics, ecological safety, simplicity and convenience of the suggested procedure exceed published methods that are based on pesticides extraction using organic solvents.

Determining heterocyclic aromatic amines in aqueous samples: A novel dispersive liquid-liquid micro-extraction method based on solidification of floating organic drop and ultrasound assisted back extraction followed by UPLC-MS/MS

A novel dispersive liquid-liquid microextraction based on solidification of floating organic droplet combined with ultrasound assisted back extraction for the determination of four heterocyclic aromatic amines in natural water samples prior ultra high-performance liquid chromatography-tandem mass spectrometry was developed. The analytes were extracted from the water samples by a dispersive liquid-liquid microextraction procedure based on solidification of floating organic drop, which was performed by a mixture composed by a less dense than water extraction solvent, 1-undecanol, and a dispersive solvent, methanol. After that, a novel ultrasound assisted back extraction step was performed in order to make the clean-up/enrichment procedure compatible with the detection requirements. Under optimum conditions, linearity ranged from 2.2 to 50ngmL−1, with enrichment factors from 130 to 136-folds. Thus limits of detection between 0.7 and 2.9ngmL−1 were obtained. Precision of the method was evaluated in terms of repeatability, relative standard deviations varied from 4.3% to 6.7%. Relative recoveries ranged from 92% to 106% for all analytes. The satisfactory performance demonstrated that the proposed methodology has a strong potential for application in the multi-residue analysis of heterocyclic aromatic amines present in complex environmental matrices.

A novel ultrasound-assisted back extraction reverse micelles method coupled with gas chromatography–flame ionization detection for determination of aldehydes in heated edibles oils

A novel ultrasound-assisted back extraction reverse micelles coupled with gas chromatography–flame ionization detection has been developed for the extraction and determination of some short chain aldehydes in different heated edible oil samples. After the homogenization of the oil samples with Triton X-100, 200μL of methanol was added to facilitate the phase separation. The aqueous micelle phase has been separated by centrifugation, then it was treated with a mixture of H2O: CHCl3 and ultrasonic vibration, were used to effectively back-extraction of the analytes into the chloroform phase. The sedimented organic phase was obtained after centrifugation, withdrawn into the microsyringe and directly injected into the GC–FID system. The calibration graphs were linear in the range 0.05–20mgL−1. The limits of detection were in the range of 0.02–0.15mgL−1. This procedure was successfully applied for determination of propanal, butanal, hexanal and heptanal in real heated oil samples.

Cloud point–dispersive μ-solid phase extraction of hydrophobic organic compounds onto highly hydrophobic core–shell Fe2O3@C magnetic nanoparticles

A novel two-step extraction technique combining cloud point extraction (CPE) with dispersive micro-solid phase extraction (D-μ-SPE) is presented in this work for the first time. The method involves initial extraction of the target analytes by CPE in the micelles of a non-ionic surfactant medium; then highly hydrophobic polysiloxane-coated core–shell Fe2O3@C magnetic nanoparticles (MNPs) are used to retrieve the micellar phase. In that manner, the micellar phase containing the analytes is the target of the D-μ-SPE step rather than the analytes directly. MNPs are then collected by the application of an adscititious magnetic field overcoming the need for specific steps associated with CPE such as centrifugation to separate the surfactant-rich phase, refrigeration of the condensed micellar phase to reduce its viscosity or appropriate apparatus that enable direct sampling of the surfactant-rich phase. A noteworthy feature of the method is the introduction of highly oleophilic MNPs, which afford rapid and quantitative mass transfer of the surfactant phase, as opposed to other more conventional hydrophobic nanoparticles. In that manner, fast and reproducible extraction is accomplished, lending improved analytical features compared to conventional CPE, such as reduced analysis time and relative inertness to surfactant concentration and equilibration temperature. The analytes were recovered from the surface of MNPs by ultrasound-assisted back-extraction in a water-immiscible organic solvent where analytes are readily partitioned but the surfactant has limited solubility, thus minimizing its interference during chromatographic detection. As an analytical demonstration, different UV absorbing chemicals with various physico-chemical properties were used as model organic compounds for optimizing the parameters associated with this novel two-step extraction approach. The proposed method, combining two different and efficient techniques, offers satisfactory analytical features in terms of repeatability (4.5–7.5%), reproducibility (7.0–14.9%) and accuracy (88.5–97.2%). Most importantly it poses as an alternative and fast method for sample pretreatment opening new insights in surfactant-mediated extractions.

Determination of β-sitosterol and cholesterol in oils after reverse micelles with Triton X-100 coupled with ultrasound-assisted back-extraction by a water/chloroform binary system prior to gas chromatography with flame ionization detection

Ultrasonic back-extraction of Triton X-100 reverse micelles by a water/chloroform binary system and gas chromatography with flame ionization detection (GC-FID) was developed for extraction and determination of β-sitosterol and cholesterol in soybean and sunflower oil samples. After the homogenization of the oil samples with Triton X-100, an aliquot of 200 μL of methanol was added to the samples to form two phases. The clear Triton X-100 extract obtained by centrifugation was treated with a mixture of water (1000 μL) and chloroform (300 μL) for back-extraction of the analytes into the chloroform phase by ultrasonication. After centrifugation, the sedimented chloroform layer was withdrawn easily by a microsyringe and directly injected into the GC-FID system. The influence of several important parameters on the extraction efficiencies of the analytes was evaluated. Under optimized experimental conditions, the calibration graphs were linear in the range of 1.0–30.0 mg L −1 with coefficient of determination more than 0.994 for both analytes. The method detection limit values were in the range of 0.2–0.7 mg L −1. The lower limit of quantification values were in the range of 0.7–2.4 mg L −1. Intra-day relative standard deviations were in the range of 1.0–2.7%. This procedure was successfully applied with satisfactory results to the determination of β-sitosterol and cholesterol in spiked oil samples. The relative mean recoveries of oil samples ranged from 93.6% to 105.0%.

Determination of Se(IV) using solidified floating organic drop microextraction coupled to ultrasound-assisted back-extraction and hydride generation atomic fluorescence spectrometry

A method is presented for matrix separation, preconcentration and determination by hydride generation atomic fluorescence spectrometry of trace amounts of Se(IV). It is based on solidified floating drops of 1-undecanol that are capable of extracting the target analyte after chelation with a water soluble ligand and subsequent ultrasound-assisted back-extraction into a aqueous solution. Hydride generation was then accomplished by reaction with a solution of sodium borohydride. Under optimized conditions, an enrichment factor of 15 and a linear calibration plot in the range from 0.01 to 5.0 μg L−1 were achieved using a 10.0 mL sample. The detection limit (3σ) is 7.0 ng L−1, and the relative standard deviation (RSD) is 2.1% at 1.0 μg L−1 (n = 11). The method was applied to determination of Se(IV) in different real water samples through recovery experiments and subsequently validated against two certified reference materials.

Determination of polybrominated diphenyl ethers in water and soil samples by cloud point extraction-ultrasound-assisted back-extraction-gas chromatography–mass spectrometry

A novel and efficient analytical methodology is proposed for extracting and preconcentrating polybrominated diphenyl ethers (PBDEs) from samples of environmental interest prior gas chromatography–mass spectrometry (GC–MS) analysis. It is based on the induction of micellar organized medium by using a non-ionic surfactant (Triton X-114) to extract the target PBDEs. To enable coupling the efficient extracting technique with GC analysis, ultrasound-assisted back-extraction (UABE) into an organic solvent was required. Several factors, including surfactant type and concentration, equilibration temperature and time, ionic strength, pH and buffers nature and concentration were studied and optimized over the extraction efficiency of the proposed technique. Under optimal experimental conditions, the target analytes were quantitatively extracted achieving an enrichment factor of 250 when 10 mL aliquot of ultrapure water spiked with PBDE-standard mixture (10 pg mL −1 each PBDE) was extracted. Method detection limits (MDLs) calculated with aqueous PBDEs solutions as three times the signal-to-noise ratio (S/N), ranged from 1 to 2 pg mL −1 with RSDs values ≤8.5% ( n = 5). The coefficients of estimation of the calibration curves obtained following the proposed methodology were ≥0.9987 and linear range of all PBDEs was 4–150 pg mL −1. The proposed methodology was validated by carrying out a recovery study by spiking the samples at two different concentration levels of PBDEs (10 and 50 pg mL −1 for waters samples). Recoveries values in the range of 96–106% for water samples were obtained showing satisfactory robustness of the method for analyzing PBDEs in water samples. The proposed methodology was applied for the analysis of PBDEs: 2,2′,4,4′-tetraBDE (BDE-47), 2,2′,4,4,5-pentaBDE (BDE-99), 2,2′,4,4,6-pentaBDE (BDE-100) and 2,2,4,4′,5,5′-hexaBDE (BDE-153) in water samples, including drinking, lake, river water and soil samples. Significant quantities of PBDEs were not found in the analyzed samples.