Chiral ligand exchange potentiometric aspartic acid sensors with polysiloxane films containing a chiral ligand N-carbobenzoxy-aspartic acid.

An enantioselective molecular sensor was fabricated by inserting a chiral ligand, N-carbobenzoxy-L-aspartic acid (N-CBZ-L-Asp) or N-CBZ-D-Asp, into an octadecylsiloxane (ODS) monolayer by polysiloxane film immobilization (PFI). The resulting system can recognize one enantiomer of aspartic acids (Asps) due to the chiral ligand exchange reaction at the N-CBZ-L-/D-Asp modified indium-tin oxide (ITO)-coated electrode. The enantioselective formation of diastereoisomeric complexes of Cu(II) with target enantiomers, in here L-/D-Asps, and N-CBZ-L-/D-Asp immobilized by PFI on the ITO electrode. Those diastereoisomeric complexes have different thermodynamic stabilities and Nernst factors and thus enable the sensors to convert the enantioselective recognition event into potential changes by detecting Asp enantiomers in a concentration range of (4.0 x 10(-8))-(8.9 x 10(-5)) M without any pre- or postseparation process. The enantiomeric selectivity coefficients of the sensors for the counterisomers were in the range of (4.0 x 10(-5))-(5.0 x 10(-5)).