Miniaturized, Membrane-Based and Environmentally Green Sample Preparation Systems: Applications for Biological and Environmental Aqueous Samples

Contemporary advancements in miniaturization of analytical systems have advantageously fostered development, automation, and hyphenation of a variety of sample preparation techniques. Among several downscaled extraction designs, porous synthetic polymeric membranes (such as flat sheet (FS) or hollow fiber (HF)) have been utilized for membrane-based extraction, separating two aqueous phases (as in supported liquid membrane (SLM) extraction or one aqueous phase and another organic phase (as in microporous membrane liquid-liquid extraction (MMLLE)). The SLM and MMLLE configurations permit usage of microliter-volumes of extraction solvent, and therefore, are considered to be environmentally friendly. This dissertation addresses miniaturized membrane-based extraction techniques that were operated in automated, flowing, and on-line fashion as well as in nonautomated, nonflowing, and off-line setups. These environmentally green systems based on SLM and MMLLE were appraised for trace extraction of organic compounds (such as basic and acidic pharmaceuticals (by SLM), and PCBs, OCPs, and PBDEs (by MMLLE)) in environmental and biological aqueous samples. Exhaustive extraction and non-depletive equilibrium extraction exhibiting high level of analyte preconcentration were demonstrated. The former was performed for total analyte recovery. The later was pursued so as to quantify free analyte concentration in a sample containing an analyte and a binding phase, such as a protein or humic acids. For instance, by measuring the free drug concentration, the level of drug-protein binding (DPB) was quantitatively estimated as well as the DPB process was characterized and interpreted by obtaining the binding parameters from Scatchard and Bjerrum plots. The results revealed that, although the flowing on-line systems exhibited excellent performance (e.g. the Extracting Syringe device permitting a full automation of a µMMLLE with an on-line hyphenation to gas chromatography in a closed system and limits of detection at very low ng L-1 concentration level), the flowing systems suffered from setup complexity, low extraction efficiency, and problems with analyte carryover and adsorption. By contrast, the nonautomated nonflowing designs allowed simplified and easy-to-use procedures, high analyte extraction efficiency and enrichment, and no carryover and no adsorption problems as the HF-SLM or HF-MMLLE device was employed for only a single use. In conclusion, the HF-based, nonautomated, and nonflowing setups of SLM and MMLLE have been shown to have attractive merits when employed for exhaustive as well as non-depletive equilibrium sampling. The latter design has strong potential applications for speciation of freely dissolved organic compounds, and a promising development is expected in its application for environmental and biological samples

Supported liquid membrane work-up of blood plasma samples coupled on-line to liquid chromatographic determination of basic antidepressant drugs

An automated sample pretreatment of human blood plasma for liquid chromatographic determination of three antidepressant drugs, dibenzepine; a tricyclic antidepressant (TCA), reboxetine; a selective noradrenaline reuptake inhibitor (SNRI) and fluvoxamine; a selective serotonin reuptake inhibitor (SSRI), based on supported liquid membrane (SLM) for unsurpassed sample clean-up and analyte enrichment, has been developed. The chromatograms after enrichment of plasma blank and aqueous blank are virtually indistinguishable. The entire analytical procedure revealed good linearity and low detection limits of 5, 15 and 20 ng mL(-1) for dibenzepine, reboxetine and fluvoxamine, respectively. No carry-over effects were noted. The repeatability of extraction at three concentrations in the range 40-150 ng mL(-1) for the three drugs was between ca. 3% and 7% as relative standard deviation. The reproducibility relative standard deviation during three different days (replacing the membrane each day) was not significantly higher

Supported-liquid membrane extraction

Supported-liquid membrane (SLM) extraction is a miniaturized version of liquid–liquid extraction (LLE), involving a hydrophobic membrane containing an organic solvent in the pores. Compared to LLE, it uses microliter-volumes of organic solvents, and provides high enrichment, outstanding clean-up and no emulsion formation. Here, basic principles and technical aspects as well as new developments in the field are discusse

Advances and developments in membrane extraction for gas chromatography: Techniques and applications.

This review article focuses on advances and technical developments of the realm of membrane extraction techniques for the analytes that are (made) amenable to gas chromatographic analysis, and sheds light on the analytical applications to biological and environmental samples. In this review, the state of the art in this growing area of membrane extraction for gas chromatography is presented and several selected examples from our work and that of other groups are discussed. The published articles on the techniques and their applications, found in the scientific literature between the years 2000 and May 2007 and cited in over than 100 references, are perused and commented. A good deal of light will be thrown on the novelty of the techniques, instrumentations and applications. The mentioned techniques are mainly microporous membrane liquid-liquid extraction, extracting syringe, two-phase hollow-fibre-protected liquid-phase microextraction and its modifications, and membrane extraction with sorbent interface and its variants. The merits and demerits of the techniques will be highlighted

A novel hollow-fibre microporous membrane liquid-liquid extraction for determination of free 4-isobutylacetophenone concentration at ultra trace level in environmental aqueous samples

In this study, a method was developed for determination of the free concentration of 4-isobutylacetophenone, a toxic degradation product of ibuprofen, in river and sewage water samples from Sweden. Sample preparation and analysis were performed by a hollow-fibre microporous membrane liquid-liquid extraction (HF-MMLLE) set-up and gas chromatography-mass spectrometry (GC-MS), respectively. In this novel approach, only the liquid in the membrane pores is utilised for non-depleting extraction. Several parameters were studied, including: type of organic solvent, sample pH, and salt and humic acid content. The optimised method allowed the determination of the analyte at the ng L-1 level in river and sewage water. A linear plot gave a correlation coefficient better than 0.992 and resulted in a limit of detection of 7 and 14 ng L-1 for river and sewage water, respectively. The enrichment factor was over 2000 in the fibre and over 300 after dilution. The repeatability and reproducibility were better than 5% and 10%, respectively. For the first time, 4-isobutylacetophenone was found at free concentrations of 40 ng L-1 or below in sewage waters, while it could not be quantified in a river downstream from a municipal sewage treatment plant

A simplified hollow-fibre supported liquid membrane extraction method for quantification of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) in urine and plasma samples

A simple and easy-to-use extraction procedure has been optimised, validated, and applied for extraction of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) in urine and spiked plasma samples. PhIP is a carcinogenic and mutagenic heterocyclic aromatic amine that is formed during cooking of meat and fish. The novelty of the extraction procedure lies in using a short piece of narrow capillary-like microporous hollow-fibre (HF) membrane as extraction device. The HF membrane was filled with a few microlitres of acidic solution and the membrane pores were impregnated with an organic extraction solvent. Therefore, the technique was called hollow-fibre supported liquid membrane (HF-SLM) extraction. The HF extraction device was then supported by a syringe needle and directly immersed in urine (1.4 mL) or plasma (0.3 mL) previously made alkaline by adding 0.5 mol L−1 NaOH solution to give a final volume of 1.6 mL. The operation of the HF-SLM extraction at the optimal conditions resulted in a PhIP extraction efficiency of 74% from both spiked urine and plasma, corresponding to enrichment factors of 126 and 27, respectively. For 90 min extraction time, limits of detection and quantification were, respectively, 8 and 25 pg mL−1 for urine and 6 and 11 pg mL−1 for plasma. Within-day repeatability (n = 6) and between-day reproducibility (n = 3) were, respectively, 5% and 13% for urine and 6% and 7% for plasma. Analysis of urine samples collected for 12 h after a volunteer had eaten 250 g well-done chicken showed the PhIP concentration was 124 ± 21 pg mL−1, calculated assuming an extraction efficiency of 74%

Determination of heterocyclic aromatic amines in human urine by using hollow-fibre supported liquid membrane extraction and liquid chromatography-ultraviolet detection system.

A hollow-fibre supported liquid membrane (HF-SLM) extraction method has been developed for determination of 11 heterocyclic aromatic amines (HCAs) in human urine samples by using high performance liquid chromatography (HPLC) equipped with an ultraviolet (UV) absorbance detector. These compounds were extracted from an alkaline urine sample (donor phase) into the organic solvent residing in the pores of a polypropylene hollow fibre and then back extracted into an acidic solution (acceptor phase) inside the lumen of the hollow fibre. After extraction, HCAs were analyzed by injecting the analyte enriched acceptor phase into the HPLC. The analyte enrichment factors ranged between 241 and 339 obtained in a 90min extraction time, and method detection limits (MDL) ranged between 0.1 and 0.5mugL(-1) with relative standard deviation (RSD) values between 3.4% and 11%. The extraction technique employed in this work is easy to use and rapid as it involves only a few minutes manipulation of each sample. It is the most economical sample preparation/preconcentration technique to our knowledge as compared to other microextraction techniques

Determination of polybrominated diphenyl ethers at trace levels in environmental waters using hollow-fiber microporous membrane liquid-liquid extraction and gas chromatography-mass spectrometry

In this study, we present a simple and easy-to-use extraction method that is based on a hollow-fiber microporous membrane liquid-liquid extraction (HF-MMLLE), as an extraction technique, followed by gas chromatography-mass spectrometry (GC-MS) to determine a group of brominated flame retardants (BFRs), polybrominated diphenyl ethers (PBDEs), at trace levels in aqueous samples. The hollow-fiber membrane (HF) filled with organic solvent was immersed into the aqueous sample, spiked with the analytes at ng l(-1) level, and stirred for 60 min. The proposed method could attain enrichment factors (E-e) up to 5200 times, after optimising parameters, such as organic solvent, stirring speed and extraction time, that affect the extraction. The HF-MMLLE-GC-MS method was successfully applied to the extraction of PBDEs from tap, river and leachate water samples with spike recoveries ranging from 85% to 110%. The method validation with reagent and leachate water samples provided good linearity, detection limits of 1.1 ng l(-1) or lower, both in reagent and leachate water, as well as satisfactory precision in terms of repeatability and reproducibility with values of % relative standard deviation (%RSD) lower than 8.6 and 16.9, respectively. (c) 2006 Elsevier B.V. All rights reserved

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 mug L-1), enrichment factors of 33-40 times, repeatable extractions (RSD 2-5%, n = 4),