Microporous Membrane Liquid-liquid Extraction Research Articles

A high-throughput sample preparation approach for the determination of nonsteroidal anti-inflammatory drugs in urine samples through membrane-based microextraction employing a green supramolecular solvent

Nonsteroidal anti-inflammatory drugs (NSAIDs) are a class of drugs with antipyretic, analgesic, and anti-inflammatory effects widely used worldwide. This study aimed at developing an environmentally friendly and high-throughput sample preparation method for the determination of six NSAIDs in urine samples followed by high-performance liquid chromatography coupled to diode-array detection (HPLC-DAD). The experimental workflow consisted of hollow-fiber microporous membrane liquid-liquid extraction (HF-MMLLE) using a supramolecular solvent immobilized into the porous of polypropylene hollow membranes (1 cm length). These membranes were attached to a 96-well plate system to permit multiple extractions simultaneously. Under the optimized conditions, limits of detection (LODs) and limits of quantification (LOQs) ranged from 6.06 to 30.3 µg/L and from 20 to 100 µg/L, respectively. The linear ranges varied from 20 to 1000 µg/L for indomethacin and diclofenac, from 50 to 1000 µg/L for ketoprofen and ibuprofen, and from 100 to 1000 µg/L for naproxen and fenoprofen. The coefficients of determination (R²) ranged from 0.9735 to 0.9997. Intraday precision ranged from 6.13 to 20.11 %, interday precision varied from 2.87 to 20.72 %, and accuracy ranged from 92.49 to 126.89 %. Moreover, the recently proposed Sample Preparation Metric of Sustainability (SPMS) was employed to evaluate the greenness of the sample preparation technique resulting in a score of 8.0, which is highly satisfactory according to the concepts of green analytical chemistry.

Evaluation of two membrane-based microextraction techniques for the determination of endocrine disruptors in aqueous samples by HPLC with diode array detection.

In this study, the viability of two membrane-based microextraction techniques for the determination of endocrine disruptors by high-performance liquid chromatography with diode array detection was evaluated: hollow fiber microporous membrane liquid-liquid extraction and hollow-fiber-supported dispersive liquid-liquid microextraction. The extraction efficiencies obtained for methylparaben, ethylparaben, bisphenol A, benzophenone, and 2-ethylhexyl-4-methoxycinnamate from aqueous matrices obtained using both approaches were compared and showed that hollow fiber microporous membrane liquid-liquid extraction exhibited higher extraction efficiency for most of the compounds studied. Therefore, a detailed optimization of the extraction procedure was carried out with this technique. The optimization of the extraction conditions and liquid desorption were performed by univariate analysis. The optimal conditions for the method were supported liquid membrane with 1-octanol for 10s, sample pH 7, addition of 15% w/v of NaCl, extraction time of 30min, and liquid desorption in 150μL of acetonitrile/methanol (50:50 v/v) for 5min. The linear correlation coefficients were higher than 0.9936. The limits of detection were 0.5-4.6μg/L and the limits of quantification were 2-16μg/L. The analyte relative recoveries were 67-116%, and the relative standard deviations were less than 15.5%.

Determination of emerging contaminants in aqueous matrices with hollow fiber-supported dispersive liquid-liquid microextraction (HF-DLLME) and separation/detection by liquid chromatography – Diode array detection

This paper describes the simultaneous combination of hollow fiber microporous membrane liquid-liquid extraction (HF-MMLLE) and dispersive liquid-liquid microextraction (DLLME) which was called hollow fiber-supported dispersive liquid-liquid microextraction (HF-DLLME). This approach is then applied to the determination of methylparaben, 3-(4-methylbenzylidene) camphor, triclocarban and chlorophenols in aqueous samples by HPLC-DAD. The extraction and liquid desorption steps in the HF-DLLME were optimized employing univariate procedures. The optimum extraction conditions were sample pH4, NaCl concentration 30%, extraction time 45min and the use hexane as an extractor solvent and methanol as a disperser solvent (total volume of 50μL). Liquid desorption was carried out for 15min with 100μL of acetonitrile. The quantification limits varied between 2 and 10μgL−1. The method showed recovery values between 78 and 135%.

Determination of persistent cyclic organochlorine residues in sediment slurry by microporous membrane liquid-liquid extraction and gas chromatography-mass spectrometry

A method, using microporous membrane liquid-liquid extraction technique (MMLLE) and gas chromatography with an electron capture detector (GC-ECD) and gas chromatograph coupled to a mass spectrometer, was developed for the analysis of cyclic organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) in sediment slurry. The MMLLE extraction employed isooctane as the organic liquid that was immobilised in the hollow fibre pores and in the lumen, at optimal sample pH value of 2.0 for OCPs and 7 for PCBs. The effect of triton x-100, in enhancing the dissolution of the compounds from sediment, was found to be optimal at a value of 0.15%, while the ionic strength was optimal at a value of 0.01 M. Samples from coastlines along the Indian Ocean in the southern parts of South Africa were found to be contaminated with cis and trans chlordane at concentrations of up to 0.003 mg/kg, while samples from northern parts were contaminated with 2,2’,4’,4-tetrachloro-1,1’biphenyl at concentrations of up to 0.02 mg/kg.Keywords: Organochlorine pesticides, polychlorinated biphenyls, hollow fibre liquid phase micro-extraction, high performance liquid chromatography, mass spectrometry

Hollow-Fiber Microporous Membrane Liquid-Liquid Extraction for Determination of Polybrominated Diphenyl Ethers at Trace Levels in Sewage Sludge with Gas Chromatography-Electron Capture Detection

A two-phase hollow-fiber (HF) liquid-phase microextraction (LPME) method followed by gas chromatography was developed for quantification of 8 major polybrominated diphenyl ethers at trace level in sewage sludge. In this method the porous polypropylene hollow fibers filled with a few microliters of organic solvent, were immersed in aqueous samples of wet sludge which were spiked with the PBDEs at ng/l level. Parameters such as salt concentration, stirring speed, extraction time and pH were optimized and the optimum extraction conditions were then applied to the determination of PBDEs in sewage sludge from Kallby sewage treatment plant in Lund. The optimized method allowed detection of 5.1 µg kg–1 and 0.43 µg kg–1 of BDE-47 and 183, respectively, in dried sludge. The findings were compatible with the results from recent research on PBDEs level in sewage sludge samples from Sweden. Although BDE-209 was expected to have the highest level, it was not detected. Limit of detection, photodegradation or/and biodegradation of BDE-209 during treatment or experiment are major reasons. Low organic solvent consumption, low sample volume requirement, high preconcentration factor, simplicity without using expensive instrument for extraction and excellent sample clean-up are some important factors that make this sample preparation technique very useful for determination of PBDEs in sludge.

Potential of combining of liquid membranes and molecularly imprinted polymers in extraction of 17β‐estradiol from aqueous samples

The potential of combination of liquid membranes (microporous membrane liquid-liquid extraction) and molecularly imprinted polymers (MIPs) was performed using 17beta-estradiol (E2) as model compound. The model compound was extracted from aqueous sample through a hydrophobic porous membrane that was impregnated with hexane/ethyl acetate (3:2), which also formed part of the acceptor phase. In the acceptor phase, the compound was bound onto MIP particles that were also part of the organic phase. The potential of such combination was optimised for the type and amount of MIP particles in the organic acceptor phase, the extraction time, and the type of organic acceptor solvent. Ultrasound assisted binding of E2 onto MIP particles was also investigated. MIPs prepared by precipitation polymerization were found to be superior to those prepared by bulk polymerization. Increase in the extraction time and the amount of MIP particles in the acceptor phase led to more E2 binding onto the MIP particles. Hexane/ethyl acetate (3:2) as an organic acceptor was found to give higher E2 binding onto MIP particles compared to toluene, diethyl ether, and hexane. Ultrasound was furthermore found to increase the binding of E2 onto MIP particles. The selectivity of the technique was demonstrated by extracting wastewater and where clean chromatograms were obtained compared to liquid membrane extractions (SLMs) alone.

Determination of 2-ethylhexyl 4-(dimethylamino) benzoate using membrane-assisted liquid–liquid extraction and gas chromatography-mass spectrometric detection

A flow-cell for micro-porous membrane liquid-liquid extraction with a sheet membrane was used to extract 2-ethylhexyl 4-(dimethylamino) benzoate (EDB) from urine of solar-cream users and spiked wine samples. The cell enabled the target analyte to be extracted from 7.9 mL of donor solution into 200 microL of acceptor solution (decane). After extraction, the acceptor solution was transferred to a micro-vial for GC-MS analysis without derivation. In this work, variables affecting the enrichment factor were also studied, such as organic solvent, extraction time, recirculation flow of the donor solution through the donor chamber, presence of potassium chloride and ethanol in the donor solution and pH. The method has been evaluated in terms of linearity, sensitivity, precision, limits of detection and quantification and extraction efficiency. Limits of quantification were 1 and 3 microg L(-1) EDB for urine and wine, respectively. Quantitative analysis has been carried out by applying the method of standard additions. Within- and between-day relative standard deviations were lower than 12% and 20%, respectively. EDB was found in the urine of users of cream containing EDB in the concentration interval 1.2-7.2 microg L(-1). Therefore, this provides evidence of EDB dermal absorption and subsequent excretion through the urinary tract. EDB was not found in the analysed wine samples.

Evaluation of liquid–liquid microextraction using polypropylene microporous membranes for the determination of organophosphorus flame retardants and plasticizers in water samples

In this work, the suitability of the microporous membrane liquid–liquid extraction (MMLLE) technique for the concentration of several organophosphate esters (OPs) in water samples is assessed. Analytes were first extracted into a few microlitres of an organic solvent, immobilized in the pores of a hollow polypropylene membrane, and then determined by gas chromatography with nitrogen–phosphorus detection (GC–NPD). Main parameters controlling the efficiency of the extraction step were identified and their effects on the performance of the technique discussed. Under final working conditions, 2 cm long polypropylene membranes, containing about 7 μL of octanol in the pores, were dipped in a glass vial filled with 115 mL of water with a 30% of sodium chloride. Extractions were carried out for 12 h, at room temperature, under magnetic stirring. After that, analytes were recovered from the membrane with 0.2 mL of ethyl acetate. This extract was mixed with the internal standard (50 μL of a tripentyl phosphate solution in the same solvent) and finally reduced to ca. 50 μL. Overall enrichment factors for the optimized method ranged from 35 to 1400 times, and the achieved limits of quantification from 0.008 to 0.12 ng mL −1, depending on the considered compound. Globally, the method showed an acceptable linearity and precision for all species, except for tris(2-ethylhexyl) phosphate (TEHP). Performance of the MMLLE approach is compared with that reported for other solid- and liquid-phase microextraction techniques and its suitability for the analysis of real water samples discussed.

Determination of trace levels of dinitrophenolic compounds by microporous membrane liquid–liquid extraction in environmental water samples

A fast and simple hollow fibre-based microporous membrane liquid-liquid extraction (MMLLE) method is proposed for the determination of trace levels of dinitrophenolic compounds in water samples. The optimization step was performed using a three-variables Doehlert matrix design, involving the fibre length, the quantity of trioctylphosphine oxide (TOPO) in the acceptor phase and the extraction time. Using the established experimental conditions, some other parameters such as stirring speed, salt content, humic acids and different organic solvents as the acceptor phase were studied. Validation of the method included calibration experiments, linearity studies and determination of method LOD (MLD). The RSD was around 11% in all the experiments on different days at different concentrations. Separation and detection of four dinitrophenols were performed in 10 min with an RP-LC and a C(8 )column ACN-citric buffer gradient elution and diode array detection.

Determination of pesticides in red wines with on-line coupled microporous membrane liquid–liquid extraction-gas chromatography

Microporous membrane liquid–liquid extraction (MMLLE) was coupled on-line with gas chromatography for the determination of pesticides in wine. The MMLLE-GC provided to be efficient and selective and the method was linear, repeatable and sensitive. The limits of detection ranged from 0.05 to 2.3 μg/l and the limits of quantification were 0.2–7.5 μg/l for all the analytes using FID as detector. With MS detection LODs in the range 0.03–0.4 and LOQs of 0.3–3.5 μg/l were achieved. The method was applied to the determination of pesticides in several red wines of different origin.

Miniaturized and automated sample pretreatment for determination of PCBs in environmental aqueous samples using an on-line microporous membrane liquid-liquid extraction-gas chromatography system.

A new, fast, and automated sample pretreatment technique for determination of lipophilic organic compounds in aqueous samples has been developed and applied to the determination of polychlorinated biphenyls (PCBs) in environmental river water. It is based on miniaturized microporous membrane liquid-liquid extraction coupled on-line to gas chromatography (GC) with electron capture detection. The heart of the system that simultaneously connects the sample pretreatment step to the final GC analysis has been named the extracting syringe (ESy). The ESy carries a miniaturized membrane extraction card attached to an electrically and mechanically designed installment and is mounted directly over a GC injector for fully automated injection of the extract. A method was developed to extract 10 PCB congeners from 1-mL water samples (after addition of 40% acetonitrile) with an extraction time of 10 min. The optimized methodology showed good linearity (in the dynamic concentration range of 5 ng L(-)(1)-1 microg L(-)(1)), enrichment factors of 33-40 times, repeatable extractions (RSD 2-5%, n = 4), and low detection limits (2-3 ng L(-)(1)). Acetonitrile had to be added to the samples in order to overcome the influence of PCB adsorption on the repeatability of extraction and enrichment and to minimize the overall memory effect (OME). OME and carryover depended not only on the concentration of the organic solvent added to the sample and that used in the washing procedure but also on whether the extracting card was changed or not. When an optimized washing procedure was applied, the OME was approximately 0.2% at high concentrations (i.e., 1 microg L(-)(1)). When each extraction took place in a new extraction card, no OME was detected. Additionally, no significant adsorption onto glass surfaces or a matrix effect on extraction was noticed. The main features of this methodology are good extraction repeatability, low detection limits at short extraction time, and the unsurpassed characteristic of no detectable OME in the entire system when each sample is processed in a new card. The total consumption of organic (nonchlorinated) solvents is less than 5 mL per sample.

On-line coupling of microporous membrane liquid-liquid extraction and gas chromatography in the analysis of organic pollutants in water.

A method for the determination of hydrophobic pollutants in surface waters was developed. The pretreatment was done with microporous membrane liquid-liquid extraction, the extract was eluted to a sample loop in the large-volume injector valve of the gas chromatograph and the extract was injected on-line to the gas chromatograph. The method was optimised using standard compounds and the linearity, the limits of detection and quantification of the method were studied. The method allowed the determination of hydrophobic pesticides and PAHs at the ng L(-1) level. The RSD values for the repeatability of the method varied from 4.2% to 25.6%, being on average 9.5%. Surface water samples from Finnish lakes and rivers were analysed.

Combination of microporous membrane liquid–liquid extraction and capillary electrophoresis for the analysis of aromatic amines in water samples

A method has been established for the simultaneous analysis of eight aromatic amines in water samples by the combination of capillary zone electrophoresis and microporous membrane liquid–liquid extraction (MMLLE). Eight aromatic amines including N, N-dimethylaniline, m-methylaniline, 3,4-dimethylaniline, 2-naphthylamine, 1-naphthylamine, 4-aminobiphenyl, 2-chloroaniline and 2,4-chloroaniline were well separated under optimal separation conditions. The influence factors relevant to the MMLLE process were investigated and the final optimized parameters were used for analysis. The correlation coefficients were excellent with R 2 values larger than 0.99 and the detection limits (S/N=3) were in the range of 0.16–7.5 ng ml −1. The precision and recoveries were within the ranges of 1.7–13.5 and 78.8–112.6%, respectively.

Factors affecting microporous membrane liquid‐liquid extraction

AbstractThe effect of different factors on the extraction yield in microporous membrane liquid‐liquid extraction (MMLLE) was studied in this work. The factors were the extraction temperature, mixing of the donor and acceptor solvents, state of the acceptor (stagnant or flowing), solvent set‐up in the membrane unit (organic phase on top or bottom), adsorption of the analytes into the membrane material, and the membrane pore size. The effect of temperature, as it was mediated through the other factors, was of particular interest. Increase in the extraction temperature improved the extraction yields substantially: for naphthalene the extraction yield increased from 14.3% to 17.7% and for benz[a]anthracene from 0.4% to 11.1% when the temperature was raised from 20°C to 80°C. The diffusion coefficients, which were determined with a chromatographic band broadening method, were also clearly increased with temperature: the average diffusion coefficient obtained for naphthalene in water at ambient temperature was 7.92×10–10 m2/s, while at 70°C it was 2.19×10–9 m2/s. The most vigorous mixing of the solvents was obtained with counter‐currently flowing acceptor phase and water on top in the membrane block. The adsorption to the membrane material compared with theoretical 100% extraction yield ranged from 0.5 to 5.4% at 80°C when no acceptor phase was present.

Micro-porous membrane liquid–liquid extraction as an enrichment step prior to nonaqueous capillary electrophoresis determination of sulfonylurea herbicides

A method based on micro-porous membrane liquid–liquid extraction (MMLLE) enrichment and nonaqueous capillary electrophoresis (CE) separation, was established for the analysis of sulfonylurea herbicides in water samples. After MMLLE, the analyte trapped in the chloroform was treated mildly with nitrogen flow to dryness and then dissolved in 200 μl of 4 mM Tris methanol solution for CE analysis. Five sulfonylurea herbicides were separated by nonaqueous CE with Tris/acetate of methanol solution as the run buffer. MMLLE related parameters such as organic solvent used as acceptor, sample flow rate, sample pH, enrichment time, and salt effect were investigated with tribenuron methyl (TBM) as a model compound. Results showed that with a sample flow rate of 3.0 ml min −1 and an enrichment time of 20 min, the proposed method has good linear relationship over the scope of 1–15 ng ml −1 with related coefficient of R 2=0.9911, and a detection limit of 0.4 ng ml −1. This method was applied to determine TBM in realworld water samples with recoveries over the range of 89–97%.

On-line automated sample preparation for liquid chromatography using parallel supported liquid membrane extraction and microporous membrane liquid–liquid extraction

An automated system was developed for analysis of non-polar and polar ionisable compounds at trace levels in natural water. Sample work-up was performed in a flow system using two parallel membrane extraction units. This system was connected on-line to a reversed-phase HPLC system for final determination. One of the membrane units was used for supported liquid membrane (SLM) extraction, which is suitable for ionisable or permanently charged compounds. The other unit was used for microporous membrane liquid–liquid extraction (MMLLE) suitable for uncharged compounds. The fungicide thiophanate methyl and its polar metabolites carbendazim and 2-aminobenzimidazole were used as model compounds. The whole system was controlled by means of four syringe pumps. While extracting one part of the sample using the SLM technique, the extract from the MMLLE extraction was analysed and vice versa. This gave a total analysis time of 63 min for each sample resulting in a sample throughput of 22 samples per 24 h.

Determination of pesticide residues in red wines with microporous membrane liquid–liquid extraction and gas chromatography

A sample pretreatment method based on microporous membrane liquid-liquid extraction (MMLLE) was developed for the subsequent gas chromatographic determination of pesticides in wine. MMLLE provided efficient and selective extraction with enrichment factors in the range 3-13. The gas chromatographic separation was carried out using on-column injection and flame ionization detection. The method was linear, repeatable and sensitive. The limits of quantification were better than 0.006 mg/L for all the analytes except for iprodione (0.37 mg/L). The method was applied to the determination of pesticides in several red wines of different origin.

Determination of phenols in pyrolysis oil by on-line coupled microporous membrane liquid-liquid extraction and multidimensional liquid chromatography

An efficient and fast method was developed for the determination of phenols in pyrolysis oils. Microporous membrane liquid-liquid extraction (MMLLE) was applied in sample pretreatment and samples were analyzed by multidimensional liquid chromatography. The pyrolysis oil was dissolved in a suitable organic solvent and then continuously pumped through the donor side of the MMLLE system. The acceptor solution was a highly basic aqueous solution, which was kept stagnant during the extraction. The extract was transferred via a loop to the multidimensional LC system. Capillary electrophoresis was investigated for qualitative analysis of the extract. After separation, the phenols were identified by diode array detection and mass spectrometry. The method was quantitative, repeatable and linear, and limits of detection were in the range of 0.01–0.12%w/w.

Development of a microporous membrane liquid–liquid extractor for organophosphate esters in human blood plasma: identification of triphenyl phosphate and octyl diphenyl phosphate in donor plasma

An extractor has been developed for microporous membrane liquid–liquid extraction (MMLLE) of lipophilic xenobiotics at trace levels in biological fluids. This new construction allows the sample phase to be stirred, while the organic phase is pumped. The extractor was evaluated using human blood plasma with added organophosphate esters. The size exclusion properties of the membrane reduced lipid co-extraction by ∼94% compared to ordinary liquid–liquid extraction. In combination with a solid-phase extraction (SPE) step, the method was shown to remove plasma lipids efficiently and thus allow gas chromatographic separation of the compounds. The clean-up method described, including the SPE step, showed a high level of reproducibility, and recoveries of between 72 and 83% were obtained for five of the organophosphate esters after a 200-min extraction period. Using this technique, triphenyl phosphate and an isomer of octyl diphenyl phosphate were detected in human plasma obtained from blood donors. The concentration of triphenyl phosphate ranged between 0.13 and 0.15 μg/g plasma.

Determination of anionic surfactants in detergents by microporous membrane liquid–liquid extraction and flow injection spectrophotometry

The applicability of microporous membrane liquid–liquid extraction (MMLLE) and flow injection spectrophotometry to the determination of anionic surfactants in detergents was studied. Optimization of variables of the flow injection manifold, groove length of the MMLLE unit, and pore size of the membrane was performed. Experiments showed that the long-term reproducibility of the system was limited when the peristaltic pump and the displacement bottle arrangement were used, but the system was still applicable in routine analysis if calibration was carried out every 20 min. The proposed method has a linear range of 0.2–2 mmol l −1 sodium dodecylbenzenesulfonate (DBS) and a detection limit ( S/ N=3) of 0.1 mmol l −1 DBS. The sampling rate was 50 h −1 and the relative standard deviation was 1.8% ( n=11) at 1.0 mmol l −1 DBS level. Eleven washing powder samples were analyzed with the proposed procedure and the standard Epton method, and paired t-tests showed that there is no significant difference between these two methods.