Vortex-Assisted Liquid–Liquid Microextraction (VALLME): Applications

Quantification of trace fenuron in waste water samples by matrix matching calibration strategy and gas chromatography-mass spectrometry after simultaneous derivatization and preconcentration

This study presents a highly sensitive and accurate analytical strategy for the determination of fenuron in wastewater samples using gas chromatography-mass spectrometry (GC-MS). Simultaneous derivatization and spray-based fine droplet formation-liquid phase microextraction (SFDF-LPME) method was developed and performed to achieve low detection limits. The parameters of the derivatization and SFDF-LPME method were optimized by univariate approach to improve sensitivity and selectivity. Under the optimum SFDF-LPME-GC-MS conditions, the limit of detection (LOD) and limit of quantitation (LOQ) were found to be 0.15 and 0.49 mg/kg, respectively. In addition, the linear range was calculated as 0.51-24.50 mg/kg. Recovery studies were carried out on wastewater samples to determine the accuracy of the developed method and its applicability to real sample matrix. Matrix matching calibration strategy was applied to eliminate/reduce any possible interference effects caused by the complexity of the wastewater matrix and to increase the accuracy of the analytical results. Percent recovery results varied between 85.9 and 120.9% with small percent relative standard deviation values. These results were satisfactory in terms of the accuracy and applicability of the proposed method for wastewater samples.

Vortex- assisted liquid- liquid microextraction for the trace determination of potassium bromate in flour food products

Potassium bromate, also reported as a carcinogenic agent, commonly functions to improve flour in the baking industry to increase bread volume. In this study, a green and novel preconcentration and microextraction method, termed as vortex assisted liquid-liquid microextraction combined with UV-Vis spectrophotometry was developed and utilized for trace determination of Potassium Bromate in food samples. Furthermore, various chemometric methods have been used. Under optimum conditions, the linearity range was obtained in the range between 0.02 and 2 µg/mL. Using the proposed analytical approach, the detection limits and quantitation of KBrO₃ were 0.02 and 0.07 µg/mL, respectively. A pre-concentration factor of 22.2 was reported. The precision of the method was evaluated in the terms of repeatability and reproducibility and expressed by the relative standard deviation; the levels of them were considerably higher than 5.07 and 4.8%. The proposed approach was applied to the determination of trace bromate in different flour products.

Quadruple isotope dilution gas chromatography-mass spectrometry after simultaneous derivatization and spraying based fine droplet formation liquid phase microextraction method for the accurate and sensitive quantification of chloroquine phosphate in human serum, urine and saliva samples at trace levels

This study presents an accurate and precise analytical strategy for the determination of chloroquine phosphate at trace levels in human body fluids (urine, serum, and saliva). Simultaneous derivatization-spraying based fine droplet formation-liquid phase microextraction (SD-SFDF-LPME) method was used to derivatize and preconcentrate the analyte prior to gas chromatography-mass spectrometry (GC-MS) measurements. Acetic anhydride was employed as derivatizing agent in this study. After optimizing the SD-SFDF-LPME method, the limit of detection (LOD) and limit of quantitation (LOQ) were found to be 0.16 and 0.53 mg/kg, respectively. Quadruple isotope dilution (ID⁴) was coupled to the SD-SFDF-LPME method in order to alleviate matrix effects and promote accuracy/precision of the method. Chloroquine acetamide-d3 was firstly synthesized in our research laboratory and used as the isotopic analogue of the analyte in the ID⁴ experiments. Superior percent recovery results (99.4% - 101.0%) with low standard deviation values were obtained for the spiked samples. This validated the developed SD-SFDF-LPME-ID⁴-GC-MS method as highly accurate and precise for the determination of chloroquine phosphate at trace levels. In addition, the isotopic analogue of the analyte was obtained via the acetamide derivative of the analyte, which is an alternative to obtain isotopic analogues of organic compounds that are not accessible or commercially available.

CO2-effervescence assisted dispersive micro solid-phase extraction based on a magnetic layered double hydroxide modified with polyaniline and a surfactant for efficient pre-concentration of heavy metals in cosmetic samples

In this paper, a CO2-effervescence assisted dispersive micro solid-phase extraction procedure (CO2-EA-DμSPE) using a magnetic layered double hydroxide modified with polyaniline and a surfactant (Zn-Al-LDH-PA-DBSNa-Fe3O4) was applied for the pre-concentration of heavy metals (Ni2+, Pb2+, Co2+, and Cd2+). The final analysis of the analytes was carried out by atomic absorption spectroscopy. XRD, FTIR, and SEM studies were used for the characterization of the synthesized nanoadsorbent. For the maximum extraction efficiency, effective factors (including pH, nanoadsorbent dosage, and volume of the eluent) were investigated using the central composite design (CCD) method. Under the optimum conditions, the preconcentration factor was more than 20. The linear ranges for Ni2+, Pb2+, Co2+, and Cd2+ were obtained as (5-550), (7-750), (5-500), and (3-100) ng mL-1, respectively. The proposed method provided low detection limits (1.4, 2.1, 1.5, and 0.9 ng mL-1 for Ni2+, Pb2+, Co2+, and Cd2+, respectively) and suitable repeatability (relative standard deviation values (RSDs) below 6.1%, n = 6). Finally, the current method was successfully used for the extraction of heavy metals from cosmetic samples.

Optimized Vortex-Assisted Dispersive Liquid–Liquid Microextraction Coupled with Spectrofluorimetry for Determination of Aspirin in Human Urine: Response Surface Methodology

Background:

A Vortex-assisted dispersive liquid-liquid microextraction (VA-DLLME) method is presented for the determination of aspirin (acetylsalicylic acid) in human urine by spectrofluorimetry.

Objective:

To determine trace levels of aspirin in biologic samples by using green and low-cost method development.

Methods:

For the microextraction procedure, chloroform and acetonitrile were used as extraction and disperser solvent, respectively. The factors affecting the efficiency of extraction such as volume of chloroform, volumes of acetonitrile, ionic strength, sample pH, centrifuging time, and extraction time were investigated. Then significant variables were optimized by the response surface method using the Box- Behnken design.

Results:

Under the optimum extraction conditions, a linear calibration curve in the range of 0.1 to 130 ng mL-1 with a correlation coefficient of R2 = 0.998 was obtained. The limits of detection (LOD) and limits of quantification (LOQ) were 0.031 and 0.103 ng mL-1, respectively. The relative standard deviations (RSD) were less than 4%.

Conclusion:

Enrichment factor and recoveries were achieved for the extraction of aspirin in human urine. This method gives a rapid, simple, sensitive and environmentally friendly for the measurement of trace amount aspirin.

Determination of microcystins in water samples by deep eutectic solvent-based vortex-assisted liquid–liquid microextraction coupled with ultrahigh-performance liquid chromatography-high resolution mass spectrometry

An eco-friendly and efficient DES-based VALLME coupled UHPLC-ESI(+)-qTOF-MS method was developed to determine MC-YR and MC-LR in surface water samples.

Solvent-terminated dispersive liquid-liquid microextraction: a tutorial

Solvent-terminated dispersive liquid-liquid microextraction (ST-DLLME) is a special mode of DLLME in which a demulsifying solvent is injected into the cloudy mixture of sample/extractant to break the emulsion and induce phase separation. The demulsification process starts by flocculation of the dispersed microdroplets by Ostwald ripening or coalescence to form larger droplets. Then, the extractant either floats or sinks depending on its density as compared with that for the aqueous sample. The demulsifier should have high surface activity and low surface tension in order to be capable of inducing phase separation. The extraction efficiency in ST-DLLME is controlled by the same experimental variables of normal DLLME (n-DLLME) such as the type and volume of the extractant as well as the disperser. Other parameters such as pH and the temperature of the sample, the stirring rate, the time of extraction and the addition of salt are also important to consider. Along with these factors, the demulsifier type and volume and the demulsification time have to be optimized. By using solvents to terminate the dispersion step in DLLME, the centrifugation process is not necessary. This in turn improves precision, increases throughput, decreases the risk of contamination through human intervention and minimizes the overall analysis time. ST-DLLME has been successfully applied for determination of both inorganic and organic analytes including pesticides and pharmaceuticals in water and biological fluids. Demulsification via solvent injection rather than centrifugation saves energy and makes ST-DLLME easier to automate. These characteristics in addition to the low solvent consumption, the reduced organic waste and the possibility of using water in demulsification bestow green features on ST-DLLME. This tutorial discusses the principle, the practical aspects and the different applications of ST-DLLME.

Monitoring trihalomethanes in chlorinated waters using a dispersive liquid-liquid microextraction method with a non-chlorinated organic solvent and gas chromatography-mass spectrometry

The environmental monitoring of trihalomethanes (THMs) has been performed by setting up a dispersive liquid-liquid microextraction method in combination with gas chromatography (GC)-mass spectrometry (MS). The optimized method only requires ∼26 µL of decanol as extractant solvent, dissolved in ∼1 mL of acetone (dispersive solvent) for 5 mL of the environmental water containing THMs. The mixture is then subjected to vortex for 1 min and then centrifuged for 2 min at 3500 rpm. The microdroplet containing the extracted THMs is then sampled with a micro-syringe, and injected (1 µL) in the GC-MS. The method is characterized for being fast (3 min for the entire sample preparation step) and environmentally friendly (low amounts of solvents required, being all non-chlorinated), and also for getting average relative recoveries of 90.2-106% in tap waters; relative standard deviation values always lower than 11%; average enrichment factors of 48-49; and detection limits down to 0.7 µg·L-1. Several waters: tap waters, pool waters, and wastewaters were successfully analyzed with the method proposed. Furthermore, the method was used to monitor the formation of THMs in wastewaters when different chlorination parameters, namely temperature and pH, were varied.

Low-temperature derivatization followed by vortex-assisted liquid-liquid microextraction for the analysis of polyamines in Nicotiana Tabacum

Polyamines are ubiquitous polycationic molecules that play a key role in many biological processes such as nucleic acid metabolism, protein synthesis, cell growth, and nicotine synthesis precursors. This work describes a rapid, sensitive, convenient, green, and cost-effective method for the determination of polyamines in Nicotiana tabacum by ultra high performance liquid chromatography with photodiode array detection. The analytes were derivatized with 3,5-dinitrobenzoyl chloride at low temperature (about 4°C) and then extracted with vortex-assisted liquid-liquid microextraction. The experimental designs based on quarter-fractional factorial design and Doehlert design were used to screen and optimize the important factors in microextraction process. Under the optimal conditions, the method was linear over 0.05-8.00 μg/mL with an r(2) ≥ 0.992 and exhibited good repeatability and reproducibility less than 6.0 and 6.9%, respectively. The limit of detection ranged between 0.013 and 0.029 μg/g. The newly developed method was successfully employed to analyze different leaf samples of Nicotiana tabacum, among which the polyamines contents were found to be very different. Moreover, tyramine, 1,3-diaminopropane, homospermidine, and canavalmine were tentatively identified with the electrospray ionization quadrupole time-of-flight mass spectrometry. To our knowledge, this is the first report of identification of canavalmine in Nicotiana Tabacum.

Sensitivity enhancement in the fluorometric determination of aliphatic amines using naphthalene-2,3-dicarboxaldehyde derivatization followed by vortex-assisted liquid-liquid microextraction

A highly sensitive liquid chromatographic method was developed for the fluorometric determination of trace amounts of linear aliphatic primary amines. Prior to extraction, amines were derivatized with naphthalene-2,3-dicarboxaldehyde (NDA) in the presence of cyanide ion (CN) and extracted by vortex-assisted liquid-liquid microextraction (VALLME). The optimum conditions were as follows: derivatization reaction time for 5 min in 2.0 mL aqueous donor samples with 50 μM NDA/CN, and 10mM borate buffer at pH 9; vortex extraction time for 20s in the VALLME step with 50 μL of isooctane as the extractant phase; centrifugation for 1 min at 6000 rpm. Under the optimum conditions, the limits of detection (LOD) were between 0.01 and 0.04 nmol L(-1). The calibration curves showed good linearity in the range of 0.1-20 nmol L(-1). In comparison with previous work using o-phthalaldehyde/2-mercaptoethanol derivatization, the method has much more stable fluorescent derivatives, higher fluorescence intensities, and greater extraction efficiencies. The sensitivity enhancement factors (SEF) were between 2 and 70, which is in good agreement with the theoretical values calculated from partition coefficients in VALLME system.

Effect of type of stirring on hollow fiber liquid phase microextraction and electromembrane extraction of basic drugs: speed up extraction time and enhancement of extraction efficiency

In microextraction procedures, the stirring of the donor solution is crucial to speed up the extraction.