An advanced ratiometric molecularly imprinted sensor based on metal ion reoxidation for indirect and ultrasensitive...

An indirect and ultrasensitive ratiometric molecularly imprinted (MIP) sensor, based on metal ion reoxidation, is introduced for glyphosate (GLY) determination in fruit. As high-performance signal amplification substrates, carbon nanotubes (MWCNTs) and gold nanoparticles (AuNPs) are conveniently modified on GCE. The artificial antibody-MIP membrane, presents typical three-dimensional structure to GLY template. Built-in reference methylene blue (MB) is directly electropolymerized on MWCNTs-Au/GCE. Particularly, Cu²⁺ and GLY interestingly form chelate complex, and the Cu²⁺ (I_Cu) in Cu(Ⅱ)-GLY-complex can be reoxidized, and indirectly quantizes GLY. The reference signal (I_MB) presents noteworthy stability with different GLY levels, and the ratiometric readout (I_Cu/I_MB) is recognized as a more trustworthy indicator to quantize GLY. Proposed sensor presents broad range as 1.73 ∼ 400 ng/mL, and limit of detection is well found as 0.24 ng/mL (S/N = 3). Finally, as-fabricated method is verified with standard HPLC in real-fruit-sample, and the errors and recovery rates are calculated as 3.4% ∼ 6.7% and 94.4% ∼ 104.6%, respectively.