WO2018162611A1 - Nouveaux capteurs électrochimiques à empreinte moléculaire destinés à un perfluorooctanesulfonate et procédés analytiques basés sur ces derniers - Google Patents

Nouveaux capteurs électrochimiques à empreinte moléculaire destinés à un perfluorooctanesulfonate et procédés analytiques basés sur ces derniers Download PDF

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WO2018162611A1
WO2018162611A1 PCT/EP2018/055696 EP2018055696W WO2018162611A1 WO 2018162611 A1 WO2018162611 A1 WO 2018162611A1 EP 2018055696 W EP2018055696 W EP 2018055696W WO 2018162611 A1 WO2018162611 A1 WO 2018162611A1
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pfos
mip
electrode
templating agent
imprinted
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Paolo UGO
Najmeh KARIMIAN
Angela Maria STORTINI
Ligia Maria MORETTO
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Universita' Ca' Foscari Venezia
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
    • G01N27/28—Electrolytic cell components
    • G01N27/30—Electrodes, e.g. test electrodes; Half-cells

Definitions

  • the present invention concerns the field of the electrochemical sensors, in particular for the determination of environmental pollutants. It describes a new molecularly-imprinted sensor for polyfluorinated compounds obtained by polymerization of ortho-phenylenediamine.
  • the electrochemical analysis thanks to the ease in measuring and to the large availability of instrumentation, to the excellent limits of detection at low cost with the possibility of easy miniaturization and automation, is a widely applied method for the determination of environmental pollutants.
  • the development of innovative materials for electrodes is a key component for the future electroanalysis.
  • Molecularly-imprinted sensors are promising materials which are currently extensively studied as recognition elements or modification agents for sensors (Tran et at, Sensors and Actuators B 190 (2014) 745-751 ; Karimian et at, Biosensors & Bioelectronics 55 (2013) 492-498).
  • Molecular imprinting is a process by which specific functional monomers and crosslinking agents are polymerized in the presence of a templating molecule to form a cast-like shell. Initially, the monomers form a complex with the templating agent through covalent or non-covalent interactions. The templating agent can be removed after polymerization.
  • the MIP contains binding sites which are complementary to the target molecule with respect to size, shape, position of functional groups, and which are kept in place by the crosslinked polymer matrix.
  • a molecular memory able to selectively bind targets, is imprinted in the polymer (K.Haupt, Nature Materials, 9 (2010) 612-614).
  • the above-mentioned monomers are polymerized on an electrically conductive surface (e. g. on a gold surface) thus obtaining a MIP coated electrode (here referred to as MIP electrode).
  • MIP electrode MIP coated electrode
  • the electrical signal (redox peak) is generated by a substance which can undergo redox reaction (redox probe) present in solution which, upon applying a suitable potential, reaches the MIP electrode producing an electric current: the presence of analyte bound in the imprinted cavities of the MIP electrode opposes to the current flow through the electrode: therefore a decrease of the redox peak of the MIP electrode equilibrated with the sample, in comparison with the same MIP in a blank containing the same redox probe, but not the analyte, indicates the presence of the analyte itself, bound to MIP.
  • MIP sensors are strictly dependent on the capability of interaction between the imprintable polymer and the specific used templating agent (analyte): such interaction varies in unpredictable manner depending on the chemical and physical characteristics of the respective molecules.
  • the efficacy of such interaction determines the quality of the obtained mold, the ease in loading and unloading the analyte and, accordingly, the sensitivity, stability and reproducibility over time of the method of analysis.
  • an imprecise imprinting entails a reduced capability of binding to the target analyte and / or an increased interference caused by the binding of MIP with molecules different from the target. Therefore, the MIP sensors are always created "ad hoc", i. e.
  • critical parameters are, for example, the thickness of the produced polymer matrix, the conditions for removal of the templating agent after polymerization, the amount of imprinted templating agent, in particular the amount/ accessibility of the binding sites obtained in the polymer matrix, the usage modes of the probe during measurement, the conditions of incubation with the target analyte (time, pH, etc.).
  • a problem observed for many MIP sensors is the sensitivity decrease after a prolonged use: the cause could derive from the fact that the repeated loading and unloading of the analyte and/ or the working conditions to which the sensor is subjected, and/ or the simple exposition to environmental factors reduce the binding affinity between the analyte and the imprinted polymer.
  • a further problem lies in that the polymer imprinting technique does not necessarily result in a product which is sensitive enough to detect low concentrations of the analyte: this problem is particularly felt for those analytes which are present in traces in the environment and nevertheless need precise detection.
  • the bulk polymerization is particularly felt for those analytes which are present in traces in the environment and nevertheless need precise detection.
  • o-PD is particularly suitable for molecular imprinting, providing hydrophilic, hydrophobic and basic recognition sites through electrostatic interactions (Malintesta et al, Analytical Chemistry, 62 (1990) 2735-2740).
  • MIP sensors based on o-PD as imprinted polymer have been created for detecting various analytes, for example: kojic acid (Yang Wang et al, Talanta, 85(5), 201 1 , 2522-2527), folic acid (Karimian et al, Electrochemistry Communications, 36(2013), 92-95), ethylparaben (CN104458856), troponin T (Karimian et al, Biosensors and Bioelectronics, 50 (2013) 492-498), triclosan (Li et al, Microchemical Journal, 91 (2009) 222-226), theophylline (Kan et al Microchimica Acta, 171 , (2010) 423-429), sorbitol (Feng et al, Biosensors and Bioelectronics, 19 (2004) 1513- 1519), oxytetracycline (Li et al, Analytical Chemistry, 82 (2010) 6074-6078), glucose (Cheng et al
  • MIP sensors For the detection of perfluorooctanoic acid, MIP sensors have occasionally been described in CN-A- 104327271 and CN-A- 104880495: these sensors are based on complex composite imprintable materials which are expensive (CdTa/CdS coated with TEOS, or Agl-BiOINF) and on different methodologies of analyte detection (fluorescence or photoelectric measurements).
  • object of the present invention is a new molecularly-imprinted-polymer electrochemical sensor (herein referred to as "MIP sensor") comprising an electrically conductive surface covered with ortho-phenylenediamine (o-PD) polymerized in the presence of PFOS; after polymerization said PFOS is substantially removed.
  • MIP sensor molecularly-imprinted-polymer electrochemical sensor
  • the so created sensor shows a high sensitivity for the detection of PFOS (from 0.1 nM to 1.5 ⁇ , with a limit of detection of 0.038 nM), ad an excellent durability, highlighted by the constant current response even after prolonged use.
  • Figure 1 Cyclic voltammogram for the electropolymerization of o-PD on a gold electrode.
  • A Preparation of the MIP electrode (10 mM o-PD, 1 mM PFOS in acetate buffer (pH 5.8), 33.3% methanol, 50 mV/s, 25 cycles).
  • B Preparation of NIP electrode (same conditions as in (A) but without PFOS as templating agent).
  • Figure 2A Cyclic voltammogram obtained with MIP-modified electrodes after removal of the templating agent with methanol/ water (1 : 1 v/v) mixture for 10+ 10 min (with moderate agitation) and then 5 min with pure ethanol.
  • Solid line in 0.5 mM FcCOOH, ammonia buffer solution (pH 8.46); Dashed line: in 0.5 mM K 3 Fe(CN)6, 0.1 M KC1.
  • Figure 2B Cyclic voltammogram obtained with MIP-modified electrodes after re-washing with methanol/ water (1 : 1 v/v) mixture for 10+ 10 min (with moderate agitation) and then 5 min with pure ethanol, after 7 PFOS additions for an analysis cycle through standard additions.
  • Solid line in 0.5 mM FcCOOH, ammonia buffer solution (pH 8.46); Dashed line: in 0.5 mM K 3 Fe(CN)6, 0.1 M KC1.
  • FIG. 3 Electrochemical characterization: (A): cyclic voltammograms registered with naked gold electrode (solid line a), MIP electrode (dashed line b) and NIP electrode (dashed line c). (B): differential pulse voltammograms registered with naked gold electrode (solid line a), MIP-modified (dashed line b) and NIP-modified (dashed line c) electrode. (C): cyclic voltammograms registered with MIP (solid line) and NIP (dashed line) electrode after removal of the templating agent. (D): differential pulse voltammograms registered with MIP electrode in 0.5 mM FcCOOH (pH 8.4), before (solid line) and after (dashed line) incubation in 5 nM PFOS.
  • Figure 4 Images of a golden slide subjected to 25 o-PD electropolymerization cycles: (A) macrophotograph (scale in mm); (B) microphotograph (25 x). In both images (A) and (B) the left area shows the naked electrode, the right area shows the coated electrode.
  • Figure 5 Profilometric plot on golden slide subjected to 25 o-PD electropolymerization cycles: The region at the left of the step refers to the naked electrode, the region at the right of the step refers to the coated electrode.
  • Figure 6 Dependence of the ratio between peak current and peak width at half height on: (A) increase E, (B) amplitude, (C) pulse width and (D) sampling width with a naked gold electrode in 0.5 mM FcCOOH (pH 8.4).
  • Figure 7 Effect of different parameters on the response of the MIP electrode, expressed in terms of (i° -i), where i° and i are the current in the absence and in the presence of PFOS, respectively.
  • (Al) and (A2) Effect of the rebinding time of PFOS on the response of the MIP (Al) and NIP (A2) electrode in a 0.5 mM FcCOOH solution containing 50.0 nM PFOS for various incubation times, (B) pH effect on the binding process of the templating agent, (C) effect of the number of cycles in the electropolymerization process, (D) effect of the molar ratio between o-PD and PFOS on the response of the MIP electrode in the electropolymerization process.
  • Figure 8 Binding of PFOS with modified electrode.
  • the term "molecularly-imprinted electrochemical sensor” or “MIP sensor” or “MIP electrode” identifies any electrically conductive material partially or totally covered by a polymer matrix obtained by polymerization of an appropriate monomer in the presence of an appropriate templating agent.
  • the monomer used in the present invention is ortho-phenylenediamine (o- PD).
  • templating agent refers to the molecule used, in the o-PD polymerization step, to obtain the appropriate imprinted cavities (herein also defined as molds or binding sites) which, after removal of the templating agent, in the step of analytical determination, are able to house the analyte.
  • PFOS perfluorooctansulfonate
  • PFOS represents both the templating agent (in the step of sensor production) and the analyte to be determined (in the step of using the sensor).
  • PFOS includes herein the perfluorooctanesulfonic acid and any salt thereof, preferably alkali or alkaline-earth metal salts. In particular sodium or potassium salts.
  • PFOS can be searched, according to the invention, in any liquid environmental sample, preferably aqueous, which is desired to be assessed; environmental samples which were originally solid can also be analyzed, after their dispersion or extraction in a liquid medium, preferably aqueous.
  • the electrically conductive surface of the sensor is any metal material (or at least metal on the surface or part thereof), said metal being preferably a noble metal (i. e. gold or platinum) or a metal resistant to an oxidation potential equal to about 1 V vs Ag/AgCl, or mixtures of said metals; the metal mixtures can be homogeneous (e. g. alloys) or derived from the assembly of structures or layers of different metals, on nanometric scale too (e.g. nanoparticles).
  • the electrically conductive surface can be composed also by carbon in one of its conductive forms such as, for example, graphite, pastes or graphite-based inks, carbon fibers or nanotubes, graphene and reduced graphene oxide, carbon black, glassy carbon, doped diamond e.g. Boron-Doped Diamond (BDD), products pyrolized by polymers, including photoresist.
  • PFOS templating agent
  • the substantial absence of templating agent corresponds to the maximal availability of the binding sites obtained by polymer imprinting.
  • the substantial absence of templating agent is easily determinable by elementary analysis of the polymer matrix obtained: in particular, in a SEM-EDX spectrum, the substantial absence of the peaks corresponding to the F and/ or S atoms indicates successful removal of PFOS.
  • the term "substantial absence” of PFOS or the term “substantially removed” takes into account that, in the experimental practice, an absolute removal of all the molecules of the templating agent from the MIP is never possible; therefore, the term "substantial absence of templating agent” or “substantially removed” used in the present text admit the presence of residual templating agent in traces; the presence of such traces is non influential from the point of view of the operation of the sensor; it is instead useful as a "marker" of a sensor created according to the present invention.
  • the sensor is further functionally characterizable on the basis that (differently from a polymeric sensor non-imprinted or imprinted with templates different from PFOS), it has a significantly higher capability of binding to said PFOS.
  • the sensors of the invention have shown a remarkably high sensitivity, with a PFOS limit of detection below 0.05 nM/liter: this allows an easy determination of PFOS at concentrations in the nanomolar range, i.e. at those levels in which PFOS may be present in the environmental water, thus allowing a precise quantification of such pollutants: lacking this fine sensitivity, they would be of no practical use for quantifying this analyte.
  • the present sensors can be further characterized by having a PFOS limit of detection below 0.05 nM, typically between 0.01 and 0.05 nM/L; this allows an easy determination of PFOS concentrations in the nanomolar range.
  • the high removability of the templating agent represents a further advantage not only in the step of MIP sensor production, but also during the reference service life thereof, allowing, in the case of multiuse sensors, a substantially complete unloading of the bound analyte after each performed analysis, thus eliminating a significant interference with the successive analysis.
  • a preferred aspect of the present sensors is the degree of thickness of the polymerized o-PD on the electrically conductive layer. Such thickness is, as known in the art, easily controllable through the number of electropolymerization cycles applied.
  • the number of polymerization cycles is preferably from 22 to 28, more preferably from 24 to 26, ideally equal to 25: this allows to obtain a film with thickness generally from 50 to 200 nm (Cheng et at, Biosensors and Bioelectronics, 16 (2001) 179- 185); such thickness is non-limiting; for the purposes of the invention, thicknesses of the film in the range of about 10-500 nm, e.g. 30-400 nm or 40-300 nm or 60- 140 nm can be generally used.
  • the MIP sensor of the invention is conveniently provided in form of an electrode (MIP electrode), in embodiments already widely known: to this end, it is connected (or connectable) to an electrically conductive wire, e.g. a copper wire, in turn connected (or connectable) to a suitable current detector composed for example by a potentiostat integrated with a function generator and suitable systems of sampling of the intensity of current/ electric charge and of data acquisition/ processing.
  • a suitable current detector composed for example by a potentiostat integrated with a function generator and suitable systems of sampling of the intensity of current/ electric charge and of data acquisition/ processing.
  • any potentiostatic system of prototype or commercial type, suitable for the control of three electrode electrochemical cells can be employed.
  • Such electrodes include, without limitation: a working electrode (MIP); a counter electrode (generally made of Pt, C or another inert conductor); a reference electrode (e.g. Ag/AgCl/ KC1) or a pseudo reference electrode (ad es. Ag/
  • the MIP electrode of the invention can be provided together with the above- mentioned electrodes, as it is common knowledge for the arrangement of a potentiostatic detection system; such detection system, for the analysis of PFOS, is further object of the invention.
  • the electrochemical cell can be: a) of the classical type with the different electrodes separated and singularly insertable / replaceable in the cell which contains the electrolytic solution; b) in integrated and miniaturized form on chip on which the electrodes are imprinted by serigraphic processes (screen-printed electrodes), and/ or by deposition/ sputtering/ etching of conductors and insulators, and/ or by photolitography followed by pyrolysis (pyrolyzed photoresist carbon electrodes) and the like.
  • a further object of the invention is a system for the detection of PFOS comprising a MIP electrode as defined above and the further electrodes as defined above, conveniently connected to a current detector; such electrodes preferably comprise a MIP electrode as previously described, a counter electrode, a reference electrode and a possible further MIP electrode usable for comparison.
  • a further object of the invention is a process for the manufacture of the MIP sensors above described.
  • Such process in its general meaning, comprises the following steps: a) providing an electrically conductive surface; b) providing a solution comprising the monomer o-PD and the templating agent (PFOS); c) subjecting to polymerization, on said electrically conductive surface, the o-PD solution obtained in step b; d) remove said templating agent from the product of step c).
  • step c creates the intermediate resulting from step c), i.e. the result of steps a), b) c), before the removal of the templating agent.
  • the electrically conductive surface provided in step a) can be any metal material, or at least metal on its surface or part thereof), said metal being preferably a noble metal, such as e.g. gold or platinum, or carbon based conductive materials (graphite, glassy carbon, carbon black, nanotubes, graphene and derivatives, BDD etc.) pure or in mixtures; said mixtures can be homogeneous (e. g. alloys) or derived from the assembly of structures or layers of different metals.
  • the electrically conductive surface is conveniently cleaned, e.g. with solvents and/or alumina suspensions or other abrasives and/or methods based on ultrasound cleaning and / or electrochemical cleaning as well as plasma, laser and similar techniques.
  • the solution prepared in step b) is preferably an hydroalcoholic solution, buffered at a suitable pH, preferably between 5 and 7.
  • the o-PD concentration in the solution is between 6 and 14 mM, preferably 10 mM; the concentration of the templating agent, i.e. PFOS, in the solution is preferably between 0.1 and 1.4 mM.
  • the weight ratio between the used amounts of o-PD and PFOS is preferably between 5 and 20, more preferably between 7 and 15, ideally equal to 10.
  • the polymerization achieved in step c) is preferably performed with the electropolymerization technique.
  • the parameters for the o-PD electropolymerization are known in the art and can be possibly modified if convenient.
  • it is possible to perform polymerization cycles by applying a suitable number of scans (preferably between 22 and 28, more preferably between 24 and 26, ideally 25) of cyclic voltammetry between 0 and 1.5 V (vs. Ag/AgCl) at a scan speed of 50 mV/sec, or the like, typically between 20 and 500 mV/sec, but not limited to these values.
  • an electropolymerization at fixed and controlled potential (potentiostatic) or at controlled current intensity (galvanostatic) can be performed.
  • the intermediate product of step c), i.e. the sensor as previously described, before the removal of the templating agent is per se a further object of the present invention.
  • step d) the removal of the templating agent is generally obtained by using an hydroalcoholic solution or another suitable solvent medium.
  • the sensor obtained in step c) is immersed in the solution in agitation conditions for a suitable time, e.g. between 10 and 30 minutes.
  • the solution is a water: methanol solution in proportion between 1.5: 1 and 1 : 1.5, ideally 1 : 1.
  • the above-mentioned solutions proved particularly effective in removing the templating agent, showing at the same time an optimal capability of: penetrating in the polymer matrix, dissolving and washing the PFOS incorporated therein, and being easily separable from the polymer matrix by evaporation.
  • the solution has also proved to be inert with respect to the polymer matrix, avoiding to alter the cavities imprinted by the templating agent.
  • the MIP sensor obtained in this way can be conveniently dried with standard techniques, e.g. under air or nitrogen flow, and/or vacuum exposition, and/ or heating.
  • a further object of the invention is a method of detection of PFOS characterized by the use of a MIP sensor as described above.
  • the detection is mostly qualitative, so as to allow a rapid screening on an even large number of samples; nevertheless, the current sensors show a response which is proportional within specific analyte concentration ranges, such as to allow also a quantitative determination; they further display a high response sensitivity within a PFOS concentration range from 0.1 nM to 1.5 ⁇ , said range including the concentrations at which these analytes are generally found in polluted environmental samples, with a very low limit of detection, equal to 0.038 nM.
  • the present MIP sensors can be used for the determination of PFOS present in any liquid sample, preferably aqueous, or in a solid sample conveniently dispersed in a liquid medium, preferably aqueous.
  • the present MIP sensors are employed for the detection of PFOS in liquid media comprising food or biological samples, e.g. blood; said liquid media can be environmental water (e.g.
  • liquid media can consist in the food or biological sample itself, if liquid, such as e.g. blood, milk, beverages, etc.
  • liquid such as e.g. blood, milk, beverages, etc.
  • the very high sensitivity shown by the present sensors quite unusual for MIP sensors, makes them especially useful in the present methods, given the very low concentrations at which PFOS are present in the environment. They represent therefore an ideal tool for detecting PFOS concentrations which exceed the admissible limits established by current regulatory guidelines.
  • the use of the present MIP sensors occurs by generally known procedures.
  • the MIP electrode is immersed in said liquid sample in which a suitable redox probe has been previously been solubilized; by means of the MIP electrode and the other two electrodes contained in the measurement cell (i.e. the reference electrode and the counter electrode) cyclic voltammograms or DPV (Differential Pulse Voltammetry) or SWV (Square Wave Voltammetry) are then registered; by way of a non-limiting example, for a typical DPV measurement the following measurement parameters can be used: potential range from 0 to 0.5 V (vs.
  • the Applicant has experimentally identified the best incubation conditions for the present sensors, i.e. the duration of the measurement and the pH of the solution to be tested, in order to further increase the efficiency (sensitivity) of the measurement.
  • Useful values to this end were a duration between 5 and 25 minutes, preferably between 10 and 20 minutes, ideally 15 minutes, and a pH between 6.5 and 10.5, preferably between 7.5 and 9.5, ideally 8.4.
  • the usable redox probe can be chosen among the ones currently available, e.g. ferrocyanide based compounds.
  • the current sensors do not show a sensitivity decay over time after repeated measurements (as it typically occurs for this kind of sensors) if, during such measurements, a ferrocenecarboxylic acid (FcCOOH) is used as a redox probe.
  • FcCOOH ferrocenecarboxylic acid
  • such probe is used within a concentration range from 0.1 and 1 mM, more preferably from 0.25 and 0.75 mM, ideally 0.5 mM, at a pH between 6.5 and 10.5, preferably between 7.5 and 9.5, ideally 8.4.
  • o-phenylenediamine o-PD, ⁇ 98%, Sigma Aldrich
  • ferrocenecarboxylic acid FcCOOH ⁇ 97%, Aldrich
  • potassium salt of the perfluorooctanesulfonic acid PFOS, ⁇ 98%, Sigma Aldrich
  • perfluorooctanoic acid PFOA, ⁇ 96%, Sigma Aldrich
  • perfluorohexan sulfonate PHxS, ⁇ 98%, Sigma Aldrich
  • PFHxA perfluorohexanoic acid
  • All the other reagents were of analytical grade and the solutions were prepared using double-distilled deionized water. All the electrochemical measurements were performed at room temperature with a potentiostat CH660B controlled by a software. A three electrodes standard configuration was used. A gold disk (2.0 mm diameter), a platinum wire and an Ag/AgCl/KCl electrode (3M) were respectively used as working electrodes, counter electrode and reference electrode. The scanning electron microscopy (SEM) was performed with an Hitachi TM3000 equipped with an analysis system EDX SwiftED-3000.
  • Electropolymerization In order to prepare a MIP electrode, the surface of a gold electrode was cleaned with a damp suspension of allumina of progressively finer (1.0, 0.3 and 0.05 ⁇ ) granulometry and it was subsequently washed alternately in an ultrasound cleaner with double-distilled water for two minutes. Successively, the electrode was subjected to cyclic potential variations between 0.2 and 1.5 V with respect to Ag/AgCl in 0,5 M H2SO4 until obtaining a stable cyclic voltammogram.
  • the electrosynthesis of the o-PD film was performed through cyclic voltammetry (25 scans) between 0 and 1.0 V with respect to Ag/AgCl at a scan speed equal to 50 mV/s in an acetate buffer solution (0. 1 M, pH 5.8) and methanol (33.3% v/v) containing 10.0 mM o-PD.
  • PFOS was added in solution as templating molecule before polymerization at a concentration of 1.0 mM.
  • a control electrode modified with a non-imprinted polymer (NIP) was obtained in the same way, without adding PFOS as templating agent. The modified electrodes were dried under air flow and stored at room temperature.
  • the modified electrode was washed with water and then with solution of water and methanol (1 : 1 , v/v) for 20 minutes under moderate agitation, followed by washing with methanol to remove the templating molecule trapped in the film.
  • FIG. 1A A typical cyclic voltammogram registered during the o-PD electro-polymerization in the presence of PFOS on gold electrode is shown in Figure 1A.
  • a significant reduction of the anodic peak corresponded to the irreversible oxidation of the monomer to form an insulating thin film on the surface of the electrode during the continuous cyclization.
  • Figure IB shows the voltammograms registered during o-PD electrodeposition in the absence of the templating agent.
  • NIP monomer alone
  • the same main oxidation peak was observed at about 0.4 V, followed by a second peak at 0.72 V, as typically observed for the polymerization of pure o-PD.
  • the ferrocyanide have been used as redox probe suitable to monitor analyte capture/ release in/ from the imprinted cavities.
  • the probe cannot penetrate to reach the underlying gold surface of the electrode; viceversa when the cavities are free (absence of the analyte) the probe generates its typical voltammetric signal.
  • Figure 4A shows the MIP film deposited on a gold flat electrode obtained by 25 polymerization cycles in the presence of PFOS, while Figure 4B shows the same film observed by optical stereomicroscope.
  • the thickness of said film was measured by means of an ALPHA step profilometer and a typical profile is depicted in Figure 5.
  • the mean thickness of three films independently prepared by applying 25 electro-polymerization cycles was assessed from the mean height variation on the Y axis (in Angstrom in the graphic) between the portion of naked gold (on the left) and the portion covered with MIP (on the right); such thickness is 170 ⁇ 12 nm. Both optical and profilometrical observations indicate a complete and homogeneous covering of the electrode surface with MIP.
  • FIG 9 shows the patterns of EDX analysis confirming the existence of the grafted polymer on the surface of the transducer.
  • the signals of sulfur S and of the fluorine F are relative to the elementary composition of the templating agent PFOS which, together with the signal of carbon C, clearly indicate the modification of the surface.
  • the slightly higher carbon level present on the MIP membrane with respect to the NIP membrane can be explained by the fact that the templating agent PFOS validates the successful synthesis of polymer nanoparticles molecularly imprinted with PFOS.
  • the following table shows the chemical composition estimated by elementary analysis of the polymer film.
  • the incubation step is usually a simple and efficient way to increase sensitivity of the imprinted sensor (Xie et at, Microchim. Acta, 169 (2010) 145- 152).
  • the time of accumulation of PFOS in solution using MIP- and NIP-modified electrodes was optimized.
  • the imprinted electrode was incubated in an agitated solution containing 50.0 nM PFOS for various incubation times.
  • Signal variation is expressed in terms of (i° -i), where i° and i are the current in the absence and in the presence of PFOS, respectively.
  • the relationship between the changes of response current and rebinding time was studied in the range between 5 and 20 minutes.
  • the amount and the quality of the recognition sites of the molecularly imprinted polymer is a direct function of the amount of templating agent (Nezhadali et al, Sensors and Actuators, B, 171 (2012) 1 125- 1 131).
  • the monomer concentration in the polymerization process influences the thickness of the deposit and the amount of imprinted molecules in the polymer matrix, which in turn further influences the electrochemical behavior of the sensor (Kan et at, Sensors and Actuators, B, 168 (2012) 395-401).
  • the effect of the ratio between o-PD and PFOS on the response of the MIP electrode was studied.
  • the MIP films were electropolymerized in solution at a constant PFOS concentration (1 mM) and varying o-PD concentrations in the range 0.5-20 mM.
  • PFOS concentration 1 mM
  • o-PD concentrations 0.5-20 mM.
  • Figure 7D after PFOS extraction, the response of FcCOOH to the modified electrode is increased with increasing ratio of o- PD/PFOS from 0.5: 1 to 10: 1 , which was possibly attributed to an unstable MIP film on the surface of the electrode since too little o-PD was used.
  • the optimal ratio o-PD/PFOS is chosen at 10.
  • LOD Limit Of Detection
  • the reproducibility of manufacture of the imprinted electrodes was estimated by determining the PFOS level using three electrodes produced independently in identical experimental conditions.
  • the relative standard deviation (RSD) was 7.7% at the PFOS concentration of 5.0 nM. 2.1 1 Sample analysis

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Abstract

Selon la présente invention, le perfluorooctanesulfonate (PFOS) est un tensioactif utilisé dans une variété de produits industriels. En raison des caractéristiques de persistance, de bioaccumulation et de toxicité (PBT), la pollution provenant du PFOS est un problème d'intérêt général. La présente invention décrit la fabrication et la caractérisation d'un nouveau capteur destiné à un PFOS basé sur un polymère à empreinte moléculaire (MIP) préparé par électropolymérisation de poly-ortophénylènediamine (o-PD), sur une électrode appropriée en présence de PFOS en tant que moule moléculaire ou agent structurant (modèle). Après polymérisation, les molécules d'agent structurant sont sensiblement éliminées de la matrice polymère par lavage à l'aide d'une solution hydroalcoolique. Des procédés électrochimiques sont utilisés pour surveiller le processus d'électropolymérisation, l'élimination de l'agent structurant et la liaison, de préférence en présence d'acide ferrocènecarboxylique (FcCOOH) en tant que sonde électrochimique. La couche imprimée est caractérisée par une voltamétrie cyclique (CV), une voltampérométrie à impulsions différentielles (DPV) et une microscopie électronique à balayage (MEB). Certains facteurs qui influencent la performance de l'électrode modifiée par MIP sont décrits et optimisés. L'électrode, avantageusement utilisable dans la plage de concentration variant de 0,1 nM à 1,5 mu M, ayant une limite de détection égale à 0 038 nM (S/N = 3), a une excellente capacité de reconnaissance qualitative et quantitative du PFOS.
PCT/EP2018/055696 2017-03-09 2018-03-08 Nouveaux capteurs électrochimiques à empreinte moléculaire destinés à un perfluorooctanesulfonate et procédés analytiques basés sur ces derniers WO2018162611A1 (fr)

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WO2020236435A1 (fr) * 2019-05-23 2020-11-26 Battelle Memorial Institute Plate-forme d'impédance fluidique pour la détection et la quantification in situ de pfas dans les eaux souterraines
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