A poly(acrylic acid)-modified copper-organic framework for electrochemical determination of vancomycin.

A copper(II) benzene-1,3,5-tricarboxylate (BTC) metal-organic framework (MOF) was modified with poly(acrylic acid) (PAA) and then used in an electrochemical sensor for vancomycin. The MOF, synthesized via a single-pot method, has enhanced solubility and dispersibility in water as compared to HKUST-1 but without compromising its crystallinity and porosity. The MOF was placed on a glassy carbon electrode (GCE) where it shows enhanced electrocatalytic properties. This is assumed to be due to the presence of the poly(acrylic acid) that forms a network between various HKUST-1 crystals through dimer formation between the carboxy groups of BTC and PAA. This also led to better dispersion of the MOF and to improved interaction between MOF and vancomycin. The structural, spectral and electrochemical properties of the MOFs and their vancomycin complexes was characterized. The modified GCE is shown to be a viable tool for electrochemical determination (best at a working potential of 784 mV vs. Ag/AgCl) of the antibiotic vancomycin in spiked urine and serum samples. Response is linear in the 1-500 nM vancomycin concentration range, and the detection limit is 1 nM, with a relative standard deviation of ±4.3%. Graphical abstractSchematic representation of a method for determination of vancomycin. Poly(acrylic acid) modified HKUST-1 (P-HKUST-1) forms a complex with vancomycin [Van-P-HKUST-1] which is coated over glassy carbon electrode (GCE). The decrease in peak current is recorded as response to vancomycin via cyclic voltammetry.

Electrochemically reduced graphene oxide/Poly-Glycine composite modified electrode for sensitive determination of l-dopa.

A facile preparation strategy based on electrochemical technique for the fabrication of glycine (Poly-Gly) and electrochemically reduced graphene oxide (ERGO) composite modified electrode was developed. The morphology of the developed composite (ERGO/Poly-Gly) was investigated using field emission scanning electron microscope (FE-SEM). The composite modified glassy carbon electrode (GCE) was characterized using fourier transform-infrared (FT-IR) spectroscopy, electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The electrochemical characterization results revealed that ERGO/Poly-Gly modified GCE has excellent electrocatalytic activity. Further, it was employed for sensing of l-dopa in pH5.5. Differential pulse voltammetry (DPV) was used for the quantification of l-dopa as well as for the simultaneous resolution of l-dopa and uric acid (UA). The LOD (S/N=3) was found to be 0.15µM at the proposed composite modified electrode. Determination of l-dopa could also be achieved in the presence of potentially interfering substances. The sensor showed high sensitivity and selectivity with appreciable reliability and precision. The proposed sensor was also successfully applied for real sample analysis.