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Two-step local functionalization of fluoropolymer Dyneon THV microfluidic materials by scanning electrochemical microscopy combined to click reaction
Laboratoire Sciences Analytiques Bioanalytiques et Miniaturisation - Kadhirvel P, Combès A, Bordron L, Pichon V
Anal. Bioanal. Chem - 411(8) 1525-1536 - doi: 10.1007/s00216-019-01586-8 - 2019
A molecularly imprinted polymer (MIP) was designed in order to allow the selective solid-phase extraction of carbamazepine (CBZ), an anticonvulsant and mood-stabilizing drug, at ultra-trace level from aqueous environmental samples. A structural analog of CBZ was selected as a dummy template and different synthesis conditions were screened. The selectivity of the resulting imprinted polymers was evaluated by studying the retention of CBZ in a solvent similar to the one used for the synthesis. The presence of imprinted cavities in the polymers was then demonstrated by comparing the elution profiles (obtained by using MIP and a non-imprinted polymer, NIP, as a control) of the template, of CBZ, and of a structural analog of CBZ. Then, the extraction procedure was further optimized for the treatment of aqueous samples on the two most promising MIPs, with special attention being paid to the volume and composition of the percolation and washing solutions. The best MIP provided a highly selective retention in tap water with 81% extraction recovery for CBZ in the elution fraction of the MIP and only 14% for NIP. The repeatability of the extraction procedure was demonstrated for both tap and river waters (RSD below 4% in river water) for the drugs CBZ, oxcarbamazepine, and one metabolite (carbamazepine 10,11-epoxide). A MIP capacity of 1.15 μmol g-1 was determined. Finally, an analytical procedure involving the MIP was developed allowing the detection of CBZ at a concentration level of only a few nanograms per liter in river water. The selectivity provided by the MIP resulted in a 3000-fold increase of the signal-to-noise ratio in LC/MS analysis as compared to the use of conventional sorbent. Graphical abstract.
First profiling in hydrophilic interaction liquid chromatography of intact human chorionic gonadotropin isoforms.
Laboratoire Sciences Analytiques Bioanalytiques et Miniaturisation - Camperi J, Pichon V, Fournier T, Delaunay N
J Pharm Biomed Anal - 10;174 495-499. - doi: 10.1016/j.jpba.2019.06.014 - 2019
The study of glycoproteins is a rapidly growing field, which is not surprising considering that approximately 70% of human proteins are glycosylated and that numerous biological functions are associated to the glycosylation. In this work, our interest focused on the heterodimeric human Chorionic Gonadotropin (hCG) glycoprotein that is the specific hormone of the human pregnancy, consisting of an α and a β subunit, so-called hCGα and hCGβ, respectively. This protein possesses a very high structural heterogeneity, essentially due to the presence of 8 glycosylation sites, but also other types of post-translational modifications. In this study, for the first time, the potential of hydrophilic interaction liquid chromatography (HILIC) was investigated to separate the intact hCG isoforms. Three different HILIC stationary phases were tested using an hCG-based drug as standard, a recombinant hCG. For each stationary phase, the effect of the initial mobile phase composition based on ACN/H2O mixture, the slope of the gradient, the content and nature of the acidic additive (formic acid and trifluoroacetic acid (TFA)), and the addition of a volatile salt (ammonium formate) on the retention and the resolution were studied. The best HILIC separation was obtained with the amide column and a mobile phase composed of water/ACN containing 0.1% of TFA. The repeatability in terms of retention times and peak areas was then assessed. Finally, the method was applied to the analysis of a second hCG-based drug obtained from urine of pregnant women. Both drugs gave chromatograms with more than 10 peaks. However, they were significantly different, which demonstrated the potential of HILIC method for hCG isoform fingerprinting
Online coupling of immunoextraction, digestion, and microliquid chromatography-tandem mass spectrometry for the analysis of sarin and soman-butyrylcholinesterase adducts in human plasma
Laboratoire Sciences Analytiques Bioanalytiques et Miniaturisation - Maud Bonichon, Valentina Valbi, Audrey Combès, Charlotte Desoubries, Anne Bossée & Valérie Pichon
- 410 pages1039–1051 - doi.org/10.1007/s00216-017-0640-z - 2018
Organophosphorus nerve agent (OPNA) adducts formed with human butyrylcholinesterase (HuBuChE) can be used as biomarker of OPNA exposure. Indeed, intoxication by OPNAs can be confirmed by the LC/MS2 analysis of a specific HuBuChE nonapeptide on which OPNAs covalently bind. A fast, selective, and highly sensitive online method was developed to detect sarin and soman adducts in plasma, including immunoextraction by anti-HuBuChE antibodies, pepsin digestion on immobilized enzyme reactors (IMER), and microLC/MS2 analysis of the OPNA adducts. The potential of three different monoclonal antibodies, covalently grafted on sepharose, was compared for the extraction of HuBuChE. The online method developed with the most promising antibodies allowed the extraction of up to 100% of HuBuChE contained in plasma and the digestion of 45% of it in less than 40 min. Moreover, OPNA-HuBuChE adducts, aged OPNA adducts, and unadducted HuBuChE could be detected (with S/N > 2000), even in plasma spiked with a low concentration of OPNA (10 ng mL−1). Finally, the potential of this method was compared to approaches involving other affinity sorbents, already described for HuBuChE extraction.
Human odor and forensics: Towards Bayesian suspect identification using GC × GC–MS characterization of hand odor
Laboratoire Sciences Analytiques Bioanalytiques et Miniaturisation - lVincent Cuzuel Roman Leconte Guillaume Cognon Didier Thiébaut Jérôme Vial Charles Sauleau Isabelle Rivals
Journal of Chromatography B - 1092 379-385 - https://doi.org/10.1016/j.jchromb.2018.06.018 - 2018
A new method for identifying people by their odor is proposed. In this approach, subjects are characterized by a GC × GC–MS chromatogram of a sample of their hand odor. The method is based on the definition of a distance between odor chromatograms and the application of Bayesian hypothesis testing. Using a calibration panel of subjects for whom several odor chromatograms are available, the densities of the distance between chromatograms of the same person, and between chromatograms of different persons are estimated. Given the distance between a reference and a query chromatogram, the Bayesian framework provides an estimate of the probability that the corresponding two odor samples come from the same person. We tested the method on a panel that is fully independent from the calibration panel, with promising results for forensic applications.
Active modulation in neat carbon dioxide packed column comprehensive two-dimensional supercritical fluid chromatography
Laboratoire Sciences Analytiques Bioanalytiques et Miniaturisation - Orjen Petkovic Pierre Guibal Patrick Sassiat Jérôme Vial Didier Thiébaut
ELSEVIER - 1536 176-184 - https://doi.org/10.1016/j.chroma.2017.08.063 - 2018
After demonstrating in a first paper the feasibility of SFCxSFC without decompression of the mobile phase, a modified interface has been developed in order to perform active modulation between the two SFC dimensions. In this paper, it is shown that the new interface enabled independent control of modulation parameters in SFCxSFC and performed a band compression effect of solutes between the two SFC dimensions. The effectiveness of this new modulation process was studied using a Design of Experiments. The SFCxSFC prototype was applied to the analysis of a real oil sample to demonstrate the benefits of the active modulator; in comparison to our previous results obtained without active modulation, better separation was obtained with the new interface owing to the peak compression occurring in the modulator.
Zinc oxide nano-enabled microfluidic reactor for water purification and its applicability to volatile organic compounds
Laboratoire Sciences Analytiques Bioanalytiques et Miniaturisation - Imadeddine Azzouz, Yamina Ghozlane Habba, Martine Capochichi-Gnambodoe, Frédéric Marty, Jérôme Vial, Yamin Leprince-Wang & Tarik Bourouina
Microsystems & Nanoengineering - 4 17093 - 10.1038/micronano.2017.93 - 2018
This paper reports fast and efficient chemical decontamination of water within a tree-branched centimeter-scale microfluidic reactor. The microreactor integrates Zinc oxide nanowires (ZnO NWs) in situ grown acting as an efficient photocatalytic nanomaterial layer. Direct growth of ZnO NWs within the microfluidic chamber brings this photocatalytic medium at the very close vicinity of the water flow path, hence minimizing the required interaction time to produce efficient purification performance. We demonstrate a degradation efficiency of 95% in <5 s of residence time in one-pass only. According to our estimates, it becomes attainable using microfluidic reactors to produce decontamination of merely 1 l of water per day, typical of the human daily drinking water needs. To conduct our experiments, we have chosen a laboratory-scale case study as a seed for addressing the health concern of water contamination by volatile organic compounds (VOCs), which remain difficult to remove using alternative decontamination techniques, especially those involving water evaporation. The contaminated water sample contains mixture of five pollutants: Benzene; Toluene; Ethylbenzene; m–p Xylenes; and o-Xylene (BTEX) diluted in water at 10 p.p.m. concentration of each. Degradation was analytically monitored in a selective manner until it falls below 1 p.p.m. for each of the five pollutants, corresponding to the maximum contaminant level (MCL) established by the US Environmental Protection Agency (EPA). We also report on a preliminary study, investigating the nature of the chemical by-products after the photocatalytic VOCs degradation process.
Analytical methods for the monitoring of post-combustion CO2 capture process using amine solvents: A review
Laboratoire Sciences Analytiques Bioanalytiques et Miniaturisation - Lorena Cuccia José Dugay Domitille Bontemps Myriam Louis-Louisy Jérôme Vial
ELSEVIER - 4 17093 - https://doi.org/10.1016/j.ijggc.2018.03.014 - 2018
Post-combustion CO2 capture is considered to be the most promising technology to limit the CO2 emissions from existing fossil fuel power plants. One of the main problems associated with the CO2 capture process is the degradation of amine solvents, which can negatively impact both human health and the environment. Degradation products are formed in the liquid phase of the solvent, but can also be emitted with the gaseous effluents, increasing the need for monitoring strategies. The present review proposes a critical analysis of the literature concerning the analytical strategies developed in the field of post-combustion capture to identify and quantify the main classes of degradation products formed; specifically amines, amides, aldehydes, nitrosamines and organic acids. Regarding the liquid phase, the principal analytical methods involved are Liquid Chromatography (LC) and Gas Chromatography (GC) for the analysis of amines and Ionic Chromatography (IC) for the analysis of organic and inorganic acids. Concerning aldehydes, the most described method is derivatization of the compounds with 2,4-dinitrophenylhydrazine prior to LC analysis. In order to monitor the gaseous effluents, four methods have been described: FTIR, implementation of impingers, online MS analysis and sampling on solid sorbents.
Two-step local functionalization of fluoropolymer Dyneon THV microfluidic materials by scanning electrochemical microscopy combined to click reaction
Laboratoire Sciences Analytiques Bioanalytiques et Miniaturisation - Cyrine Slim, Eva Ratajovà, Sophie Griveau, Frédéric Kanoufi, David Ferraro, Camille Perréard, Fanny d’Orlyé, Anne Varenne and Fethi Bedioui
Electrochemistry Communications - 60 (5–8) - doi:10.1016/j.elecom.2015.07.019 - 2015
We propose an original two-step strategy combining the use of scanning electrochemical microscopy (SECM) and molecular chemistry via a “click” reaction (copper (I)-catalyzed azide alkyne cycloaddition (CuAAC)) to locally functionalize Dyneon THV surfaces, an attractive fluoropolymer for microfluidic applications. The first step consists in the local reduction of THV using a SECM tip to activate the surface by the creation of a locally carbonized zone and notably the formation of surface alkyne functions. This is then followed by a direct CuAAC reaction with an azide-bearing ligand for its local immobilization. The proof of concept is demonstrated by efficient local functionalization of the substrate with a fluorescent dye stable up to 6 months. Surface modifications were characterized by IR-ATR, XPS, and fluorescence microscopy.
Silica sputtering as a novel collective stationary phase deposition for microelectromechanical system gas chromatography column: Feasibility and first separation
Laboratoire Sciences Analytiques Bioanalytiques et Miniaturisation - J. Vial, D. Thiébaut, F. Marty, P. Guibal, R. Haudebourg, K. Nachef, K. Danaie, B. Bourlon
J. Chrom. A - 1218(21) :3262-66 - DOI:10.1016/j.chroma.2010.12.035 - 2011
Since the late 1970s, approaches have been proposed to replace conventional gas chromatography apparatus with silicon-based microfabricated separation systems. Performances are expected to be improved with miniaturization owing to the reduction of diffusion distances and better thermal management. However, one of the main challenges consists in the collective and reproducible fabrication of efficient microelectromechanical system (MEMS) gas chromatography (GC) columns. Indeed, usual coating processes or classical packing with particulate matters are not compatible with the requirements of collective MEMS production in clean room facilities. A new strategy based on the rerouting of conventional microfabrication techniques and widely used in electronics for metals and dielectrics deposition is presented. The originality lies in the sputtering techniques employed for the deposition of the stationary phase. The potential of these novel sputtered stationary phases is demonstrated with silica sputtering applied to the separation of light hydrocarbons and natural gases. If kinetic characteristics of the sputtered open tubular columns were acceptable with 2500 theoretical plates per meter, the limited retention and resolution of light hydrocarbons led us to consider semipacked sputtered columns with rectangular pillars allowing also significant reduction of typical diffusion distances. In that case separations were greatly improved because retention increased and efficiency was close to 5000 theoretical plates per meter.
Selective extraction of nitroaromatic explosives by using molecularly imprinted silica sorbents
Laboratoire Sciences Analytiques Bioanalytiques et Miniaturisation - S. Lordel, F. Chapuis-Hugon, V. Eudes, V. Pichon
Anal. Bioanal. Chem - 399(1) :449-58 - DOI:10.1007/s00216-010-4346-8 - 2011
Two molecularly imprinted silicas (MISs) were synthesized and used as selective sorbents for the extraction of nitroaromatic explosives in post-blast samples. The synthesis of the MISs was carried out with phenyltrimethoxysilane as monomer, 2,4-dinitrotoluene (2,4-DNT) as template and triethoxysilane as cross-linker by a sol-gel approach in two molar ratios: 1/4/20 and 1/4/30 (template/monomer/cross-linker). Non-imprinted silica sorbents were also prepared following the same procedures without introducing the template. An optimized procedure dedicated to the selective treatment of aqueous samples was developed for both MISs for the simultaneous extraction of the template and other nitroaromatic compounds commonly used as explosives. The capacity of the MISs was measured by the extraction of increasing amounts of 2,4-DNT in pure water and is higher than 3.2 mg/g of sorbent for each MIS. For the first time, four nitroaromatic compounds were selectively extracted and determined simultaneously with extraction recoveries higher than 79%. The potential of these sorbents was then highlighted by their use for the clean-up of post-blast samples (motor oil, post-mortem blood, calcined fragments, etc.). The results were compared to those obtained using a conventional sorbent, thus demonstrating the interest of the use of these MISs as selective sorbents.
Surface Reactivity from Electrochemical Lithography: Illustration in the Steady-State Reductive Etching of Perfluorinated Surfaces
Laboratoire Sciences Analytiques Bioanalytiques et Miniaturisation - H. Hazimeh, S. Nunige, R. Cornut, C. Lefrou, C. Combellas, F. Kanoufi
Anal. Chem. - 83(15) :6106-13 - DOI:10.1021/ac201255c - 2011
The scanning electrochemical microscope (SECM) in the lithographic mode is used to assess quantitatively, from both theoretical and experimental points of view, the kinetics of irreversible transformation of electroactive molecular moieties immobilized on a surface as self-assembled monolayers (SAMs). The SECM tip allows the generation of an etchant that transforms the surface locally and irreversibly. The resulting surface patterning is detectable by different surface analyses. The quantification of the surface transformation kinetics is deduced from the evolution of the pattern dimensions with the etching time. The special case of slow etching kinetics is presented; it is predicted that the pattern evolution follows the expansion of the etchant at the substrate surface. The case of a chemically unstable etchant is considered. The model is then tested by inspecting the slow reductive patterning of a perfluorinated SAM. Good agreement is found with different independent SECM interrogation modes, depending on the insulating or conducting nature of the covered substrate. The surface transformation measurements are also compared to the reduction of solutions of perfluoroalkanes. The three-orders-of-magnitude-slower electron transfer observed at the immobilized molecules likely describes the large reorganization associated with the generation of a perfluoroalkyl-centered radical anion.
Feasibility of ultra high performance supercritical neat carbon dioxide. chromatography at conventional pressures
Laboratoire Sciences Analytiques Bioanalytiques et Miniaturisation - C. Sarazin, D. Thiebaut, P. Sassiat,J. Vial
J. Sep. Sci. - 34(19) :2773-8 - DOI:10.1002/jssc.201100332 - 2011
The implementation of columns packed with sub-2 µm particles in supercritical fluid chromatography (SFC) is described using neat carbon dioxide as the mobile phase. A conventional supercritical fluid chromatograph was slightly modified to reduce extra column band broadening. Performances of a column packed with 1.8 µm C18-bonded silica particles in SFC using neat carbon dioxide as the mobile phase were compared with results obtained in ultra high performance liquid chromatography (UHPLC) using a dedicated chromatograph. As expected and usual in SFC, higher linear velocities than in UHPLC must be applied in order to reach optimal efficiency owing to higher diffusion coefficient of solutes in the mobile phase; similar numbers of theoretical plates were obtained with both techniques. Very fast separations of hydrocarbons are presented using two different alkyl-bonded silica columns.
Micropillar array chips toward new immunodiagnosis
Laboratoire Sciences Analytiques Bioanalytiques et Miniaturisation - H.Y. Li, V. Dauriac, V. Thibert, H. Senechal, G. Peltre, X.X. Zhang, S. Descroix
Lab. Chip - 10(19) :2597-604 - DOI:10.1039/c005034b - 2010
In this paper, we demonstrate the possibility to use a micropillar array to perform molecular immunodiagnosis. A polydimethylsiloxane (PDMS) microdevice consisting of a rectangular array of micropillars (45 µm in height, 100 × 100 µm square cross section) was used to replace microchannels or gels (polyacrylamide or agarose) to perform electrokinetic separation. This microarray was used to mimic highly diluted gel and to maintain electrolyte within the pillar zone by capillary effect. The electrolyte composition (glycerol and agarose content) was investigated in order to improve protein separation by isoelectric focusing (IEF). The influence of glycerol on focusing time and on the different evaporative contributions was further evaluated. In order to perform an immunodiagnostic of milk allergy, different surface treatments were optimized to prevent milk allergen adsorption on PDMS surface. Poly(dimethylacrylamide)-co-allyl glycidyl ether (PDMA-AGE) as well as gelatin led to a satisfactory signal to noise ratio. Finally the possibility to perform protein mixture separation using this micropillar array chip followed by immunoblotting was demonstrated by using the serum from an allergic individual, confirming the great potential of this analytical platform in the field of immunodiagnosis.
Total on-line analysis of a target protein from plasma by immunoextraction, digestion and liquid chromatography-mass spectrometry
Laboratoire Sciences Analytiques Bioanalytiques et Miniaturisation - A. Cingöz, F. Hugon-Chapuis, V. Pichon
J. Chrom. B - 878(2) :213-21 - DOI:10.1016/j.jchromb.2009.07.032 - 2010
A total on-line analysis of a target protein from a plasma sample was made using a selective immunoextraction step coupled on-line to an immobilized enzymatic reactor (IMER) for the protein digestion followed by LC-MS/MS analysis. For the development of this device, cytochrome c was chosen as model protein due to its well-known sequence. An immunosorbent (IS) based on the covalent immobilization of anti-cytochrome c antibodies on a solid support was made and an immunoextraction procedure was carefully developed to assess a selective extraction of the target protein from plasma. For the first time, IS was easily coupled on-line with a laboratory-made IMER based on pepsin. The whole on-line device (IS-IMER-LC-MS/MS) allowed the quantification of cytochrome c from 8.5pmol to 1.7nmol in buffer medium. Finally, this device was applied to the analysis of only 85pmol of cytochrome c from plasma with a RSD value lower than 10% (n=3).
Supercritical fluid chromatography hyphenated with twin comprehensive two-dimensional gas chromatography for ultimate analysis of middle distillates
Laboratoire Sciences Analytiques Bioanalytiques et Miniaturisation - F. Adam, D. Thiébaut, F. Bertoncini, M. Courtiade, M.C. Hennion
J. Chrom. A - 1217(8) :1386-94 - DOI:10.1016/j.chroma.2009.11.092 - 2010
This paper reports the conditions of online hyphenation of supercritical fluid chromatography (SFC) with twin comprehensive two-dimensional gas chromatography (twin-GCxGC) for detailed characterization of middle distillates; this is essential for a better understanding of reactions involved in refining processes. In this configuration, saturated and unsaturated compounds that have been fractionated by SFC are transferred on two different GC x GC columns sets (twin-GCxGC) placed in the same GC oven. Cryogenic focusing is used for transfer of fractions into the first dimension columns before simultaneous GCxGC analysis of both saturated and unsaturated fractions. The benefits of SFC-twin-GC x GC are demonstrated for the extended alkane, iso-alkane, alkene, naphthenes and aromatics analysis (so-called PIONA analysis) of diesel samples which can be achieved in one single injection. For that purpose, saturated and unsaturated compounds have been separated by SFC using a silver loaded silica column prior to GC x GC analysis. Alkenes and naphthenes are quantitatively recovered in the unsaturated and saturated fractions, respectively, allowing their identification in various diesel samples. Thus, resolution between each class of compounds is significantly improved compared to a single GCxGC run, and for the first time, an extended PIONA analysis of diesel samples is presented.
Indirect Grafting of Acetonitrile-Derived Films on Metallic Substrates
Laboratoire Sciences Analytiques Bioanalytiques et Miniaturisation - A. Berisha, C. Combellas, F. Kanoufi, J. Pinson, S. Ustaze, F.I. Podvorica
Chem. Mater - 22(9) :2962-9 - DOI:10.1021/cm100295n - 2010
Strongly bonded organic films with amino groups are obtained on gold, copper, and silicon surfaces by reduction of 2,6-dimethyl benzenediazonium in acetonitrile (ACN). The sterically hindered 2,6-dimethylphenyl radical is unable to attach to the surface, but it abstracts an hydrogen atom from ACN to give the cyanomethyl radical (·CH2CN) that reacts with the surface. A spontaneous reaction is also possible on copper. The film is characterized by IR spectroscopy, scanning electron microscopy, ellipsometry, water contact angles, and cyclic voltammetry. A mechanism is elaborated that accounts for the formation, grafting of the cyanomethyl radical, and finally formation of amino multilayers.
Determination of Cocaine in Human Plasma by Selective Solid-Phase Extraction Using an Aptamer-Based Sorbent
Laboratoire Sciences Analytiques Bioanalytiques et Miniaturisation - B. Madru, F. Chapuis-Hugon, E. Peyrin, V. Pichon
Anal. Chem. - 81(16) :7081-6 - DOI:10.1021/ac9006667 - 2009
A complete characterization is presented of a highly selective solid-phase extraction (SPE) sorbent which exploits the properties of aptamers. An oligosorbent based on aptamers immobilized on a solid support was synthesized and tested for the selective extraction of cocaine from human plasma. Anticocaine aptamers were immobilized to CNBr-activated Sepharose, and an extraction procedure was developed in pure media. Specific retention of cocaine on the oligosorbent was demonstrated, and the capacity of the support was determined. This oligosorbent was then applied to the selective extraction of cocaine from plasma at a concentration of 0.4 mg L(-1), i.e., corresponding to the plasma concentration reached after an intake of a single dose of cocaine. Extraction recovery close to 90% was obtained. Moreover, interfering compounds that perturbed cocaine quantification when using a standard SPE sorbent were not retained on the oligosorbent, thus allowing fast and reliable analyses of plasma samples with an estimated limit of detection of 0.1 microg mL(-1).
Online preconcentration using monoliths in electrochromatography capillary format and microchips
Laboratoire Sciences Analytiques Bioanalytiques et Miniaturisation - V. Augustin, G. Proczek, J. Dugay, S. Descroix, M.C. Hennion
J. Sep. Sci. - 30(17) :2858-65 - PMID:17973277 - 2007
Online preconcentration and separation of analytes using an in situ photopolymerized hexyl acrylate-based monolith stationary phase was evaluated using electrochromatography in capillary format and microchip. The band broadening occurring during the preconcentration process by frontal electrochromatography and during the desorption process by elution electrochromatography was studied. The hexyl acrylate-based monolith provides high retention for neutral analytes allowing the handling of large sample volumes and its structure allows rapid mass transfer, thus reducing the band broadening. For moderately polar analytes such as mono-chlorophenols that are slightly retained in water, it was shown that enrichment factors up to 3500 can be obtained by a hydrodynamic injection of several bed volumes for 120 min under 0.8 MPa with a decrease in efficiency of 50% and a decrease of 30% for the resolution between 2- and 3-chlorophenol. An 8 min preconcentration time allows enrichment factors above 100 for polyaromatic hydrocarbons. The interest of these monoliths when synthesized in microchip is also demonstrated. A 200-fold enrichment was easily obtained for PAHs with only 1 min as preconcentration time, without decrease in efficiency.

18 publications.