A multi-walled carbon nanotubes/cellulose acetate composite electrode (MWCNT/CA) as sensing probe for the amperometric determination of some catecholamines

Abstract

Abstract A morphological and electroanalytical characterization of a glassy carbon electrode modified with multi-walled carbon nanotubes dispersed into cellulose acetate polymer matrix (GC/MWCNT/CA), was reported. The morphology of the modified electrode reveals a favorable distribution of the carbonaceous fibers interconnected within the cellulose acetate matrix, showing an improved active surface area. The electrode was tested as an sensing probe for the detection of some important catecholamines such as dopamine and epinephrine using cyclic volatmmetry and differential pulse voltammetry (DPV) in 50 mM H3PO4. Under DPV conditions, the detection limits of the investigated catecholamines are comprised between 1 μM and 10 μM. A reverse phase chromatographic technique (pH 3.5), coupled with the GC/MWCNT/CA amperometric sensor was optimized for the separation and quantification of the tested catecholamines. Under the optimized conditions, the investigated analytes, including an important urinary catecholamine metabolite such as the vanillylmandelic acid, were eluted and separated in about 10 min with good chromatographic efficiency and resolution. The effects of various common interferents on the analytical signal, were also evaluated. A solid phase extraction pre-concentration procedure accomplished with chromatography and electrochemical detection allows the possibility to lower the detection limits of the investigated molecules at level of 1–5 nM. Real samples of pharmaceutical vials and urine samples were successful analyzed using the proposed amperometric sensor in two different analytical contexts: DPV and amperometry after solid phase extraction procedure coupled with liquid chromatography.