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A melamine acoustic chemosensor based on molecularly imprinted polymer film

Agnieszka Pietrzyk 1Wlodzimierz Kutner 1Raghu Chitta 2Melvin E. Zandler 2Francis D'Souza 2Francesco Sannicolò 4Patrizia R. Mussini 3

1. Polish Academy of Sciences, Institute of Physical Chemistry, Kasprzaka 44/52, Warszawa 01-224, Poland
2. Wichita State University, Department of Chemistry, 1845, Fairmount, Wichita, KS 67260-0051, United States
3. University of Milan (UNIMI), Via Festa del Perdono 7, MILANO 20122, Italy
4. Università degli Studi di Milano, Dipartimento di Chimica Organica e Industriale, via Venezian 21, Milano 20133, Italy


A melamine piezomicrogravimetric (acoustic) chemosensor using a molecularly imprinted polymer (MIP) film was devised and tested.  A melamine-templated MIP film and a 10 MHz AT cut shear thickness mode bulk acoustic wave quartz crystal resonator with Pt film electrodes served as the recognition element and signal transducer of the chemosensor, respectively.  The MIP films were prepared by electrochemical polymerization, performed under simultaneous cyclic voltammetry (CV) and piezoelectric microgravimetry (PM) conditions, using an electrochemical quartz crystal microbalance (EQCM), on the Pt/quartz resonator substrates.  For MIP preparation, the melamine template was first complexed in solution by a functional monomer of the bis(bithiophene) derivative bearing an 18 crown 6 substituent, at the monomer to template mole ratio of 3 : 1, and then electrochemically polymerized.  The structure of the MIP-melamine complex was visualized by DFT B3LYP/3-21G(*) energy optimization calculations.  Sensitivity and selectivity of the MIP film was largely increased if the polymer was crosslinked with bithianaphthene monomer.  Moreover, the presence of an ionic liquid, used as a porogenic solvent of the pre polymerization solution, additionally enhanced sensitivity of the chemosensor.  The ionic liquid played also a role of the supporting electrolyte in the electropolymerization.  After electropolymerization, the melamine template was extracted by soaking the MIP film in an aqueous strong base solution.  The UV-vis spectroscopy, XPS, and electrochemical measurements confirmed extraction of the melamine template from the MIP film.  Additionally, the SECM imaging bore out removal of the melamine template from the MIP film and then rebinding of the melamine analyte.  The AFM and SEM imaging emphasized relative roughness and porosity, respectively, of the MIP films.  The analytical as well as some kinetic and thermodynamic parameters of the chemosensing were assessed under flow injection analysis (FIA) conditions with PM detection.  The melamine dynamic concentration range was at least 5 nM to 1 mM.  The lower concentration limit of detection was as low as ~5 nM melamine.  The chemosensor was selective with respect to common interferants, such as cyanuric acid, cyromazine, and ammeline.

Scheme.  Excerpt of structural formula of the MIP-melamine film.


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Presentation: Short communication at SMCBS'2009 International Workshop, by Agnieszka Pietrzyk
See On-line Journal of SMCBS'2009 International Workshop

Submitted: 2009-09-11 13:18
Revised:   2009-10-30 13:01