Effect of GO nanosheets on spectrophotometric determination of tyrosine in urine and serum using nitrosonaphthol.

Here, we aimed to use graphene oxide to improve the selectivity and sensitivity of Tyr determination via the reaction with 1-nitroso-2-naphthol as a selective reagent of Tyr. The reaction between Tyr and 1-nitroso-2-naphthol in absence and presence of GO was studied spectrophotometrically. Different parameters such as concentrations, temperature, incubation time were optimized. The obtained data showed that the maximum absorbance was achieved by using 2 mL of 0.03% 1-nitroso-2-naphthol at temperature 60 °C for 10 min. On the basis of calibration curve of various concentrations of Tyr in the presence of 20 μg mL-1 GO, the limit of detection was 6.4 × 10-6 M (1.15 μg mL-1), where in absence of GO was 1.1 × 10-5 M (19.9 μg mL-1). The selectivity of Tyr in presence of other amino acids and phenols was studied with and without GO. The data obtained revealed that the selectivity of Tyr in presence of GO with respect to some amino acids and phenols was improved. The proposed method has been applied for the determination of Tyr in urine and serum samples. Therefore, GO is a powerful catalytic surface for the sensitive and selective determination of Try in biological fluids.