Solvent Microextraction Techniques Research Articles

Automated primary amine-based supramolecular solvent microextraction with monoterpenoid as coacervation agent before high-performance liquid chromatography

The phenomenon of the formation of a supramolecular solvent based on a primary amine during dispersion in the aqueous phase of a homogeneous mixture containing both an amphiphile (primary amine) and a coacervation agent (monoterpenoid) was presented. In this case, the addition of a solid monoterpenoid during microextraction was not required. The established approach has the potential for automation based on a flow system, since only liquid phases are involved in the formation of a supramolecular solvent. An automated primary amine-based supramolecular solvent microextraction technique with monoterpenoid as a coacervation agent was developed. The microextraction procedure was carried out inside a mixing chamber of a flow-batch system. Dispersion of the amphiphile and coacervation agent mixed solution in the phase of the aqueous sample was performed by using air bubbles supplied by a peristaltic pump. The technique was applied to the separation and preconcentration of bisphenol A from beverages for its chromatographic determination as a model analytical method. The supramolecular solvent precursors mixed solution contained both 1-hexylamine and menthol provided extract phase separation without centrifugation, high extraction recovery (90 ± 8 %), and compatibility of the extract phase with a mobile phase used for chromatographic analysis. The linear range was 2–5000 µg L−1 with a determination coefficient of 0.999. The limit of detection calculated from a blank test based on 3σ was 0.7 µg L−1. The limit of quantification calculated from a blank test based on 10 σ was 2 µg L−1. The enrichment factor was found to be 10.4. The intra-day repeatability was less than 8 % while inter-day repeatability was less than 10 %; relative recovery values were in the range of 84–102 %.

Pharmacokinetic determination and analysis of nortriptyline based on GC-MS coupled with hollow-fiber drop-to-drop solvent microextraction technique.

A simple, sensitive and robust technique of hollow-fiber drop-to-drop solvent microextraction coupled with GC-MS has been successfully developed for the detection of antidepressant drug nortriptyline in human blood and urine samples. The recoveries of the drug from the spiked samples are found to be well within the range and appropriate to support the method. The LOD for the drug was obtained to be 0.007, 0.009 and 0.021μg ml-1 in deionized water, urine and blood samples of human subjects, respectively. Linearity was obtained over the concentration range of 0.5-5.0mg l-1 in deionized water with correlation coefficient 0.99672.

Hollow-Fibre-Supported Dispersive Liquid-Liquid Microextraction for Determination of Atrazine and Triclosan in Aqueous Samples.

We report the application of the dispersive liquid-liquid microextraction coupled to hollow-fibre membrane-assisted liquid-phase microextraction and its application for extraction of atrazine and triclosan. Under optimum conditions, namely, 25 μL of a 1 : 4 chlorobenzene : ethyl acetate mixture dispersed in 1 mL of aqueous sample, 10% (m/v) NaCl, a magnetic stirrer speed at 600 rpm, and 10 minutes' extraction time with toluene-filled fibre as the acceptor phase, the method demonstrates sufficient figures of merit. These include linearity (R2 ≥ 0.9975), intravial precision (%RSD ≤ 7.6), enrichment factors (127 and 142), limits of detection (0.0081 and 0.0169 µg/mL), and recovery from river water and sewerage (96–101%). The relatively high detection limits are attributed to the flame ionization detector which is less preferred than a mass spectrometer in trace analyses. This is the first report of a homogenous mixture of the dispersed organic solvent in aqueous solutions and its employment in extraction of organic compounds from aqueous solutions. It therefore adds yet another candidate in the pool of miniaturised solvent microextraction techniques.

The development of a high-throughput measurement method of octanol/water distribution coefficient based on hollow fiber membrane solvent microextraction technique.

This paper describes the development of a novel high-throughput hollow fiber membrane solvent microextraction technique for the simultaneous measurement of the octanol/water distribution coefficient (logD) for organic compounds such as drugs. The method is based on a designed system, which consists of a 96-well plate modified with 96 hollow fiber membrane tubes and a matching lid with 96 center holes and 96 side holes distributing in 96 grids. Each center hole was glued with a sealed on one end hollow fiber membrane tube, which is used to separate the aqueous phase from the octanol phase. A needle, such as microsyringe or automatic sampler, can be directly inserted into the membrane tube to deposit octanol as the accepted phase or take out the mixture of the octanol and the drug. Each side hole is filled with aqueous phase and could freely take in/out solvent as the donor phase from the outside of the hollow fiber membranes. The logD can be calculated by measuring the drug concentration in each phase after extraction equilibrium. After a comprehensive comparison, the polytetrafluoroethylene hollow fiber with the thickness of 210 μm, an extraction time of 300 min, a temperature of 25 °C and atmospheric pressure without stirring are selected for the high throughput measurement. The correlation coefficient of the linear fit of the logD values of five drugs determined by our system to reference values is 0.9954, showed a nice accurate. The -8.9% intra-day and -4.4% inter-day precision of logD for metronidazole indicates a good precision. In addition, the logD values of eight drugs were simultaneously and successfully measured, which indicated that the 96 throughput measure method of logD value was accurate, precise, reliable and useful for high throughput screening.

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

Recently, a new and fast equilibrium-based solvent microextraction technique termed vortex-assisted liquid–liquid microextraction was developed. In this technique, the dispersion of the extraction solvent is enhanced by vortex mixing. The aim of the present review is to discuss the applications of vortex agitation in solvent-microextraction procedures.

Vortex-assisted liquid–liquid microextraction coupled with high performance liquid chromatography for the determination of furfurals and patulin in fruit juices

A fast and simple solvent microextraction technique using salting out-vortex-assisted liquid-liquid microextraction (salting out-VALLME) was developed for the extraction of furfurals (2-furfural (2-F), 3-furfural (3-F), 5-methylfurfural (5-MF) and 5-hydroxymethylfurfural (5-HMF)) and patulin (PAT) in fruit juice samples. The optimum extraction conditions for 5 mL sample were: extraction solvent, 1-hexanol; volume of extractant, 200 µL; vortex time, 45 s; salt addition, 20%. The simultaneous determination of the furfurals and PAT were investigated using high performance liquid chromatography coupled with diode array detector (HPLC-DAD). The separation was performed using ODS Hypersil C18 column (4.6 mm i.d × 250 mm, 5 μm) under gradient elution. The detection wavelengths used for all compounds were 280 nm except for 3-F (210 nm). The furfurals and PAT were successfully separated in less than 9 min. Good linearities (r(2)>0.99) were obtained within the range 1-5000 μg L(-1) for all compounds except for 3-F (10-5000 µg L(-1)) and PAT (0.5-100 μg L(-1)). The limits of detection (0.28-3.2 µg L(-1)) were estimated at S/N ratio of 3. The validated salting out-VALLME-HPLC method was applied for the analysis of furfurals and PAT in fruit juice samples (apple, mango and grape).

Recent Advances in Liquid Microextraction Techniques Coupled With Ms For Determination of Small-Molecule Drugs in Biological Samples

Sample preparation is an important and necessary step in a measurement process for isolation and concentration of desired components from complex matrices. It is the most time-consuming and error-prone step in analytical methodology, greatly affecting quality and quantity of analytical data. During the past 15 years, solvent microextraction techniques have been introduced as alternatives to conventional sample preparation methods, such as liquid-liquid extraction and solid-phase extraction. These novel methodologies, which have proved to be extremely simple, low-cost and virtually solvent-free sample-preparation techniques provide a high degree of selectivity, sample cleanup and enrichment. The aim of the present review is to explore recent analytical applications of solvent microextraction techniques for quantification of drugs in biological samples, with particular focus on the methods involving MS as a detection system.

Extraction and separation of zirconium from hafnium using a new solvent microextraction technique

A simple method based on the dispersive liquid–liquid microextraction and a solidification of floating organic drop followed by an inductively coupled plasma-optical emission spectrometry (ICP-OES) was developed for the extraction and separation of zirconium from hafnium. In this extraction method, an appropriate mixture of acetone (disperser solvent) and 1-undecanol (extraction solvent) was injected rapidly, into the sample solution containing 2.0 mol L−1 nitric acid and metal ions in their complex form with cyanex272 and a cloudy solution was formed. After centrifugation, the test tube was cooled by inserting it into an ice bath for 5 min. The solidified 1-undecanol on the top of the solution was transferred into suitable vial and immediately melted, then, 100.0 μL of it was dissolved in 100.0 μL of 1-propanol and finally, was injected into an ICP-OES by a flow injection system for analysis. Some effective parameters on the extraction and separation of zirconium and hafnium such as type of extraction and disperser solvents and their volumes, type and concentration of ligands, and the type and concentration of acids have been evaluated and optimized. Under the optimum conditions, the selectivity factor of about 13 was obtained.

Vortex-assisted liquid–liquid microextraction of octylphenol, nonylphenol and bisphenol-A

A new and fast equilibrium-based solvent microextraction technique termed vortex-assisted liquid-liquid microextraction (VALLME) has been developed and used for the trace analysis of octylphenol, nonylphenol and bisphenol-A in water and wastewater samples. According to VALLME, dispersion of microvolumes of a low density extractant organic solvent into the aqueous sample is achieved by using for the first time vortex mixing, a mild emulsification procedure. The fine droplets formed could extract target analytes towards equilibrium faster because of the shorter diffusion distance and larger specific surface area. Upon centrifugation the floating extractant acceptor phase restored its initial single microdrop shape and was used for high-performance liquid chromatographic analysis. Different experimental parameters were controlled and the optimum conditions found were: 50 microl of octanol as the extractant phase; 20 ml aqueous donor samples; a 2 min vortex extraction time with the vortex agitator set at a 2500 rpm rotational speed; centrifugation for 2 min at 3500 rpm; no ionic strength or pH adjustment. The calculated calibration curves gave high levels of linearity yielding correlation coefficients (r(2)) greater than 0.9935. The repeatability and reproducibility of the proposed method were found to be good and the limits of the detection were calculated in the low microg l(-1) level ranging between 0.01 and 0.07 microg l(-1). Matrix effects were determined by applying the proposed method to spiked tap, river water and treated municipal wastewater samples. The proposed method was finally applied to the determination of target pollutants in real wastewater effluent samples using the standard addition method.

Determination of n-octanol–water partition coefficients by hollow-fiber membrane solvent microextraction coupled with HPLC

A novel direct method has been developed for determination of n-octanol-water partition coefficients by hollow-fiber membrane solvent microextraction (HFMSME) combined with high-performance liquid chromatography (HPLC). The compound of interest is dissolved in water with sonication and a hollow fiber containing octanol inside is placed in the sample solution to perform microextraction. After microextraction the concentrations in both the aqueous and n-octanol phases are analyzed by HPLC with UV detection. The method was evaluated with ten reference compounds and shown to be suitable for determination of the partition coefficients of organic compounds accurately, cheaply, simply, and quickly. Previously unknown n-octanol-water partition coefficients have been obtained for other compounds by use of the hollow-fiber membrane solvent-microextraction technique.

Three-phase system in solvent bar microextraction: An approach for the sample preparation of ionizable organic compounds prior to liquid chromatography

In this article, a simple new solvent microextraction technique is described for the extraction of ionizable organic compounds. This involves performing simultaneous forward- and back-extraction across an organic film immobilized in the pores of a porous polypropylene hollow fiber. Four chlorophenoxyacetic acid herbicides were chosen as model compounds. The target compounds are extracted from the stirred acidic aqueous sample (adjusted to 0.5 M HCl; donor phase) through a thin film of an organic solvent residing in the pores of a polypropylene hollow fiber; they are then finally extracted into another alkaline aqueous phase (1 M NaOH; acceptor phase). Both ends of the fiber are pressure-sealed. The acceptor phase was analyzed by liquid chromatography (LC). This method gave good enrichment (by a factor of 438–553) of the analytes in 40 min extraction time with reasonably good reproducibility. The analytical potential of the method was demonstrated by applying the method to spiked river water sample.

Solvent Microextraction with Simultaneous Back-Extraction for Sample Cleanup and Preconcentration: Quantitative Extraction

A solvent microextraction technique has been developed to perform simultaneous forward- and back-extraction across a microliter-size organic liquid membrane. The organic liquid membrane phase (o), consisting of 40 or 80 μL of n-octane, is layered over 0.5 or 1.0 mL of aqueous sample phase (a1) contained in a 1- or 2-mL microreaction vial and is stabilized against mechanical disruption by a small Teflon ring, even when the a1 phase is stirred at a speed of 2000 rpm. A 0.1- or 0.2-mL aqueous receiving phase (a2) is layered over the o phase. After extraction for a prescribed time, an aliquot of the a2 phase is injected directly into an HPLC for quantification. The technique is efficient and selective for ionizable compounds. In 30 min, the model compounds, mephentermine and 2-phenylethylamine, in the a1 phase buffered at pH 13 are 100% and 90% extracted, respectively, into the a2 phase buffered at pH 2.1. A kinetic model has been developed, based on the Whitman two-film theory, to describe the extraction process and has been verified experimentally. The technique is promising for routine applications because of its simplicity, reproducibility, selectivity, overall sample preparation time, and quantitative extraction of compounds with relatively small distribution coefficients with submilliliter volumes of aqueous back-extractant.