A molecularly imprinted copolymer based electrochemical sensor for the highly sensitive detection of L-Tryptophan

A novel L -tryptophan ( L -Trp) electrochemical sensor is fabricated, which is based on the molecularly imprinted copolymer (MIP) of dual –functional monomers and ionic liquid (i.e. 1-butyl-3-methylimidazolium hexafluorophosphate) functionalized multi-walled carbon nanotubes (MWCNTs@IL). The MWCNTs@IL is prepared via ion exchange, while the MIP is synthesized by using L -Trp as template, styrene and 4-vinylbenzoic acid as functional monomers, Triton X-100 as emulsifier , 1, 2-divinylbenzene as cross-linking reagent and K 2 S 2 O 8 as initiator. Prior to copolymerization the functional monomer 4-vinylbenzoic acid is combined with the template molecule by forming amide bond. The template molecule is eluted by hydrolysis, and rebound by electrostatic, hydrogen-bond and π-π interaction. To construct L -Trp sensor a little of Nafion is introduced to enhance the stability and to promote rebinding. The resulting sensor Nafion-MIP-MWCNTs@IL/GCE shows a wide linear range (8 nM–26 μM) and a low detection limit (6 nM). It is successfully applied to the determination of L -Trp in oral liquid and human serum samples.