Molecularly imprinted poly[bis(2,2'-bithienyl)methane] film with built-in molecular recognition sites for a piezoelectric microgravimetry chemosensor for selective determination of dopamine.

A piezoelectric microgravimetry (PM) chemosensor, featuring a film of molecularly imprinted polymer (MIP) of poly[bis(2,2'-bithienyl)methane] bearing either a 3,4-dihydroxyphenyl or benzo-18-crown-6 substituent, for selective determination of dopamine was devised and tested. A Pt/quartz resonator and a dopamine-templated MIP film, deposited by electropolymerization onto an underlayer of poly(bithiophene), served as the transducer and recognition element of the chemosensor, respectively. The UV-vis spectroscopic and XPS as well as electrochemical measurements verified completeness of the dopamine template extraction with a strong base solution. The extraction-generated molecular cavities featured recognition sites that served selective dopamine analyte binding. The SECM imaging substantiated the permeability characteristics of the template-free MIP film. The dopamine analyte was determined under FIA conditions with the PM detection. The lower limit of detection was 10nM dopamine at favorable conditions involving the 35 μL/min carrier solution flow rate and the injected sample volume of 1 mL. The sensitivity of the chemosensor increased almost fivefold when the poly(bithiophene) film coated Pt/quartz electrode was used instead of the bare Pt/quartz electrode as the substrate for deposition of the MIP film. The chemosensor successfully discriminated dopamine from structural and functional analogues, such as 2-phenylethylamine, histamine, and ascorbic acid. The optimum mean thickness of the MIP film was ∼220 nm.