HPLC-MS/MS combined with membrane-protected molecularly imprinted polymer micro-solid-phase extraction for synthetic cathinones monitoring in urine.

Synthetic cathinones are a type of drug belonging to group of new psychoactive substances (NPSs). The illicit market for these substances is characterized by the continuous introduction to the market of new analogs to evade legislation and to avoid detection. New screening and confirmation assays are therefore needed, mainly in forensic/clinical samples. In the current development, a porous membrane-protected, micro-solid-phase extraction (µ-SPE) has been developed for the assessment of several cathinones in urine. The µ-SPE device consisted of a cone-shaped polypropylene (PP) porous membrane containing the adsorbent (molecularly imprinted polymers, MIPs, synthesized for the first time for this class of drugs). MIPs were prepared using ethylone and 3-methylmethcathinone (3-MMC) as templates, ethylene glycol dimethacrylate (EGDMA) as a functional monomer, divinylbenzene (DVB) as a cross-linker, and 2,2´-azobisisobutyronitrile (AIBN) as an initiator. The prepared ethylone-based MIP and 3-MMC-based MIP have been fully characterized and evaluated as new selective adsorbents for µ-SPE. Cathinones separation/determination was performed by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). Optimum loading conditions (pH 5.0, loading for 4.0 minutes under orbital-horizontal shaking at 200 rpm) and elution conditions [2.0 mL of 75:20:5 heptane/2-propanol/ammonium hydroxide and ultrasounds assistance (37 kHz, 325 W) for 4.0 minutes] were found for ethylone-based MIP. Validation (intra-day and inter-day precision and analytical recovery) showed RSD values lower than 9 and 10% for intra-day and inter-day precision, and within the 88%-101% range for intra-day and inter-day analytical recovery.

Control de la concentración de metilmercurio en productos pesqueros para el consumo humano mediante el empleo de polímeros de impronta molecular y de nanopartículas derivatizadas / Control of the methylmercury concentration in fish and seafood products for human consumption using molecularly imprinted polymers (MIPs) and derivatized nanoparticles

Objetivo: Desarrollar un polímero de impronta molecular para la determinación de metilmercurio en muestras de alimentos de origen marino. Material y métodos: Se sintetizó un polímero de impronta molecular (MIP) que emplea fenobarbital como ligando no vinilado para unirse al metilmercurio. Se utilizó la técnica de polimerización por precipitación. El MIP sintetizado fue empleado para funcionalizar nanopartículas magnéticas con el fin de mejorar el proceso de extracción del metilmercurio de las muestras. Resultados: El MIP con fenobarbital fue aplicado para la determinación de la concentración de metilmercurio en dos materiales de referencia de concentración certificada para el análisis de muestras de alimentos marinos (BCR-463, tejido de atún, y TORT-2, hepatopáncreas de langosta). Los valores de concentración experimentales obtenidos fueron de 3,04±0,16 μg/g y 0,152±0,013 μg/g respectivamente, coincidiendo con los valores certificados de forma estadísticamente significativa (test t, 95% confianza). Conclusiones: Se ha sintetizado un MIP para la determinación de la concentración de metilmercurio a bajas concentraciones en muestras de alimentos de origen marino (AU)

Objective: The development of a molecularly imprinted polymer support for methylmercury determination in fish and seafood samples. Materials and methods: A molecularly imprinted polymer was synthesized using the precipitation technique and phenobarbital as a non-vinylated ligand for binding methylmercury. The synthesized MIP was used for the functionalization of magnetic nanoparticles in order to improve the process of methylmercury extraction from the samples. Results: The MIP prepared with phenobarbital was applied to the determination of methylmercury concentration in two certified reference materials used for fish and seafood samples analysis (BCR-463, tuna fish, and TORT-2, lobster hepatopancreas). The experimental values (3.04±0.16 μg/g and 0.152±0.013 μg/g respectively) and the certified values showed no statistically significant difference (t test, 95% confidence level). Conclusions: We have synthesized a MIP for determining methylmercury in fish and seafood samples at low concentrations (AU)

Electrochemical sensor based on chlorohemin modified molecularly imprinted microgel for determination of 2,4-dichlorophenol.

A newly designed molecularly imprinted polymer (MIP) was synthesized and successfully utilized as a recognition element of an amperometric sensor for 2,4-dichlorophenol (2,4-DCP) detection. The MIP with a well-defined structure could imitate the dehalogenative function of the natural enzyme chloroperoxidase for 2,4-DCP. Imprinted sensor was fabricated in situ on a glassy carbon electrode surface by drop-coating the 2,4-DCP imprinted microgel suspension and chitosan/Nafion mixture. Under optimized conditions, the sensor showed a linear response in the range of 5.0-100 µmol L(-1) with a detection limit of 1.6 µmol L(-1). Additionally, the imprinted sensor demonstrated higher affinity to target 2,4-DCP over competitive chlorophenolic compounds than non-imprinted sensor. It also exhibited good stability and acceptable repeatability. The proposed sensor could be used for the determination of 2,4-DCP in water samples with the recoveries of 96.2-111.8%, showing a promising potential in practical application.

Current practices for describing the performance of molecularly imprinted polymers can be misleading and may be hampering the development of the field.

A contributing factor to the labored advance of molecularly imprinting as a viable commercial solution to molecular recognition needs is the absence of a standard and robust method for assessing and reporting on molecular imprinted polymer (MIP) performance. The diversity and at times inappropriateness of MIP performance indicators means that the usefulness of the literature back-catalogue, for predicting, elucidating or understanding patterns in MIP efficacy, remains largely inaccessible. We hereby put forward the case that the simple binding isotherm is the most versatile and useful method of assessing and reporting MIP function, allowing direct comparison between polymers prepared and evaluated in different studies. In this study we describe how to correctly plot and interpret a bound / free isotherm and show how such plots can be readily used to predict outcomes, retro-analyze data and optimize experimental design. We propose that by adopting the use of correctly constructed isotherms as the primary form of data representation researchers will enable inter-laboratory comparisons, promote good experimental design and encourage a greater collective understanding of molecular imprinting.

Preparation of nano-sized Pb2+ imprinted polymer and its application as the chemical interface of an electrochemical sensor for toxic lead determination in different real samples.

In this work, a new nano-structured ion imprinted polymer (IIP) was synthesized by copolymerization of methacrylic acid-Pb(2+) complex and ethylene glycol dimethacrylate according to the precipitation polymerization. Methacrylic acid acted as both functional monomer and complexing agent to create selective coordination sites in a cross-linked polymer. A carbon paste electrode modified with IIP-nanoparticles was used for fabrication of a Pb(2+) sensitive electrode. Differential pulse stripping voltammetry method was applied as the determination technique, after open circuit sorption of Pb(2+) on the electrode and its reduction to metallic form. The IIP modified electrode showed a considerably higher response, compared to the electrode embedded with non-imprinted polymer (NIP). This indicated that the suitable recognition sites were created in the IIP structure in the polymerization stage. Various factors, effective on the response behavior of the electrode, were investigated and optimized. The introduced sensor showed a linear range of 1.0 × 10(-9) to 8.1 × 10(-7)M and detection limit of 6.0 × 10(-10)M (S/N=3). The sensor was successfully applied for the trace lead determination in different samples.

Polymers imprinted with PAH mixtures--comparing fluorescence and QCM sensors.

Molecular imprinting with binary mixtures of different polycyclic aromatic hydrocarbons (PAH) is a tool for design of chemically highly sensitive layers for detection of these analytes. Sensor responses increase by one order of magnitude compared with layers imprinted with one type of template. Detection limits, e.g. for pyrene, reach down to 30 ng L(-1) in water, as could be observed with a naphthalene and pyrene-imprinted polyurethane. Comparing sensor characteristics obtained by QCM and fluorescence reveals different saturation behaviours indicating that, first, single PAH molecules occupy the interaction centres followed by gradual excimer incorporation at higher concentrations finally leading to substantial quenching, when all accessible cavities are occupied. The plateau in the mass-sensitive measurements suggests that up to 80% of the cavities generated in the MIP are re-occupied. Displacement measurements between chrysene and pyrene revealed that for imprinted layers with very high pyrene sensitivities the signals of both PAH are additive, whereas in materials with lower pyrene uptake the two analytes replace each other in the interaction sites of the polymer.

Molecularly imprinted matrix solid-phase dispersion for extraction of chloramphenicol in fish tissues coupled with high-performance liquid chromatography determination.

The synthesis and evaluation of a molecularly imprinted polymer (MIP) as a selective matrix solid-phase dispersion (MSPD) sorbent, coupled with high-performance liquid chromatography for the efficient determination of chloramphenicol (CAP) in fish tissues are studied. The polymer was prepared using CAP as the template molecule, vinylpyridine as the functional monomer and ethylene glycol dimethacrylate as the cross-linking monomer, and sodium dodecyl sulfate as the surfactant in the presence of water as a solvent by miniemulsion polymerization. The CAP-imprinted polymers and nonimprinted polymers (NIPs) were characterized by Fourier transform IR spectroscopy, scanning electron microscopy, and static adsorption experiments. The CAP-imprinted material prepared showed high adsorption capacity, significant selectivity, and good site accessibility. The maximum static adsorption capacity of the CAP-imprinted and the NIP material for CAP was 78.4 and 59.9 mg g(-1), respectively. The relative selectivity factors of this CAP-imprinted material were larger than 1.9. Several parameters influencing the MSPD process were optimized. Finally, the CAP-imprinted polymers were used as the sorbent in MSPD to determine CAP in three kinds of fishes and resulted in satisfactory recovery in the range 89.8-101.43%. CAP-imprinted polymer as a sorbent in MSPD is better than C18 and attapulgite in terms of both recovery and percent relative standard deviation. The baseline noise was measured from a chromatogram of a blank fish sample which was treated after the MSPD procedure using CAP-imprinted polymer as a sorbent. Signal values of 3 times the noise (signal-to-noise ratio of 3) and 10 times the noise (signal-to-noise ratio of 10) were used to calculate the limit of detection and the limit of quantitation of the calibration curve. The limit of detection for CAP was 1.2 ng g(-1) and the limit of quantitation was 3.9 ng g(-1).

MMTCA recognition by molecular imprinting in interpenetrating polymer network hydrogels based on poly(acrylic acid) and poly(vinyl alcohol).

A novel IPN hydrogel designed to recognize MMTCA is prepared by applying the molecular-imprinting method. The IPN is characterized by FT-IR, DSC, and SEM. Langmuir analysis shows that an equal class of adsorption is formed in the hydrogel. The adsorption equilibrium constant and the maximum adsorption capacity are evaluated, and the effect of the pH on MMTCA adsorption is discussed. The selectivity of the imprinted polymer for MMTCA is studied in aqueous solutions of MMTCA/aspirin/riboflavin. The results suggest that the MMTCA-imprinted polymer shows superior selectivity for MMTCA as compared to riboflavin and aspirin. The reproducibility of the imprinted polymer to MMTCA is also studied.