Selective detection of l-tyrosine in the presence of ascorbic acid, dopamine, and uric acid at poly(thionine)-modified glassy carbon electrode

• Anodized glassy carbon electrode (AGCE) was modified with poly(thionine) (PTH).
• Tyr was determined using PTH/AGCE from the interferences of AA, DA, and UA.
• The sensor allows low detection limit of 0.57 μM.
• The sensor showed good stability and recoveries of Tyr from human serum samples.

A simple, sensitive, and selective electrochemical sensor for the detection of l-tyrosine (Tyr) in the presence of ascorbic acid (AA), dopamine (DA), and uric acid (UA) at physiological pH in phosphate buffer solution (PBS) was developed based on a poly(thionine)-modified anodized glassy carbon electrode (PTH/AGCE). The PTH/AGCE resolved the voltammetric signals of AA, DA, UA, and Tyr with peak potential separations (ΔEp) of ca. 157, 135, and 325 mV between AA–DA, DA–UA, and UA–Tyr, respectively, with high sensitivity. The bare GCE and anodized GCE also resolved the Tyr oxidation signals from the interferents but the sensitivity was quite low. The PTH/AGCE sensor exhibited excellent selectivity towards Tyr detection in the presence of higher concentrations of AA, DA, and UA. The differential current responses increased linearly with increasing Tyr concentration in the range of 1 to 250 μM. The sensitivity and detection limit (S/N = 3) were found to be 1.05 μA/cm2/μM and 0.57 μM, respectively. The sensor exhibited excellent stability and reproducibility and could detect the Tyr concentration in human serum samples with excellent recoveries.

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