Amperometric sensor based on multi-walled carbon nanotube and poly (Bromocresol purple) modified carbon paste electrode for the sensitive determination of L-tyrosine in food and biological samples

An amperometric sensor was developed based on multi-walled carbon nanotubes and poly (Bromocresol purple) modified carbon paste electrode, for the sensitive investigation of L-Tyrosine (Tyr). The surface morphology of the electrodes was studied using field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM) while electron impedance spectroscopy (EIS) was employed to throw light on electrode – electrolyte interface properties. The symbiotic effect of the bulk modification and electro-polymerization was evident by 5.5 times increase in the peak current compared to the bare carbon paste electrode (CPE). Cyclic voltammetry (CV) technique was used for the qualitative analysis of Tyr at the modified electrode. The amperometric results showed that the anodic current was proportional to the Tyr concentration in ranges of 2.0 μM–100.0 μM with a lower detection limit of (1.91 ± 0.27) × 10⁻⁷ M (signal/noise = 3) at physiological pH. The CV and amperometric response of Tyr was examined in the presence of co-existing bio-molecules and the results indicated that the electrode had good anti-interference ability and could be subjected easily to real sample analysis. The low cost, high sensitivity, stability, reproducibility and anti-interference ability of the sensor offer an avenue to broaden its applications. The sensor was also tested for its practical applications by spiking Tyr in milk and blood serum samples and the recoveries obtained were found to be satisfactory.