Subnanomolar determination of dopamine by electrochemical sensor based on AuNPs- MWCNTs and mannan-Os (VI) adducts

Electroactive adducts, comprising 3α,6α–mannan attached to the six-valent osmium complex with N,N,N´,N?-tetramethylenediamine (simply denoted, Man- Os (VI) tmen) was immobilized on the surface of graphite electrodes via a simple adsorption route and then covered with poly(sodium-4 styrene sulfonate) (PSS). Cyclic voltammograms of modified electrodes GE/Man-Os (VI) tmen showed a clear and well-resolved anodic peak for 1 mM of dopamine DA, ascorbate AA, and urate UA at the potential range of -50 to +350 mV vs. Ag|AgCl|(KClsat.) the sensor GE/Man-Os (VI) tmen/PSS was successfully used for sensitive and selective determination of DA in the presence of an excess concentration of AA and UA, 5 mM and 0.5 mM respectively, using differential pulse voltammetry. Under optimized conditions, the peak current densities were linear from 0.1 nM to 20 μM of DA with a sensitivity of 358 μA μΜ-1 and a detection limit LOD (3SD/slope) of 2.8 nM. Further modifying of the sensor using multiwall carbon nanotubes decorated with gold nanoparticles (AuNPs-MWCNTs) led to substantial improvement in its analytical characteristics. The linear response of the electrode modified GE/ AuNPs-MWCNT/Man-Os (VI) tmen to DA was spanned from 1 pM to 40 μM with a high sensitivity of 624.49 μA μΜ-1 and a LOD (3SD/slope) of 0.17 pM