Modified fluorine-doped tin oxide electrode with inorganic ruthenium red dye-multiwalled carbon nanotubes for simultaneous determination of a dopamine, uric acid, and tryptophan

• Modified FTO electrode was used for simultaneous determination of a DA, UA and Trp.
• For the first time, FTO was modified with Ruthenium Red dye immobilized on a MWCNTs.
• FTO showed electrochemical activity toward DA, UA and Trp at pH 3.0.
• FTO exhibits good selectivity with respect to soluble interferents from real samples.

For the first time, a modified F-doped SnO2 electrode with ruthenium red (RuRe) inorganic dye immobilized on a multi-walled carbon nanotube was been developed. The RuRe maintained high activity on this nanomaterial, catalyzing the oxidation of dopamine (DA), uric acid (UA) and tryptophan (Trp) in a simultaneous determination, which was electrochemically reduced at 0.377, 0.552 and 0.841 V versus SCE on the biosensor surface. The measurements were carried out using cyclic voltammetry in phosphate buffer solution with pH 3.0. Under optimum conditions, the biosensor showed linear response up to 283 μM for DA and 433 μM for UA and Trp with limit of detection 0.15, 0.14 and 0.14 μM for DA, UA and Trp, respectively. The analytical performance of this sensor has been evaluated for simultaneous detection of DA, UA and Trp in human serum and urine samples.

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