Non-covalent iron(III)-porphyrin functionalized multi-walled carbon nanotubes for the simultaneous determination of ascorbic acid, dopamine, uric acid and nitrite

A chloro [3,7,12,17-tetramethyl-8,13-divinylporphyrin-2,18-dipropanoato (2−)]iron(III)/multi-walled carbon nanotubes (Fe(III)P/MWCNTs) composites and a modified glassy carbon electrode (GCE) was fabricated and successfully used for the simultaneous determination of ascorbic acid (AA), dopamine (DA), uric acid (UA) and nitrite (NO2−). Fe(III)P/MWCNTs composites were characterized by ultraviolet–visible absorption spectroscopy (UV–vis) and scanning electron microscopy (SEM), and the results revealed a pair of direct redox peaks from the FeIII/FeII couple. Moreover, the combination of Fe(III)P and MWCNTs endowed the electrode with a large surface area, good biological compatibility and stability and high selectivity and sensitivity. The linear calibration plots for AA, DA and UA were obtained over the range of 14.00 μM to 2.50 mM, 0.70 μM to 3.60 mM and 5.80 μM to 1.30 mM with detection limits of 3.00 μM, 0.09 μM and 0.30 μM, respectively. Two linear calibrations for NO2− were obtained over ranges of 1.00 μM to 0.60 mM and 0.60 mM to 1.60 mM with detection limits of 0.50 μM. In addition, the modified electrode was successfully applied for the determination of analytes in urine and serum samples using the standard adding method with satisfactory results.