A novel method for tyrosine assessment in vitro by using fluorescence enhancement of the ion-pair tyrosine-neutral red dye photo probe

Abstract

A low cost and accurate method for the detection and analytical determination of tyrosine in tablet and blood serum was developed. The method was based upon measuring the fluorescence intensity of the ion associate of neutral red dye and the tyrosine (NRD⁺ TYR⁻) at 610 nm in acetonitrile at (pH 9.5, λ_ex = 350 nm). The influence of the different parameters, e.g., pH, solvent, tyrosine concentration and foreign ions concentrations that control the fluorescence intensity of the produced ion associate was critically investigated. The remarkable enhancement of the fluorescence intensity of NRD⁺ TYR⁻ ion associate in acetonitrile at 610 nm and the quenching of emission band of NRD at 380 nm by various concentrations of tyrosine was successfully used as a photo-probe for the assessment of tyrosine concentration. The calibration plot was achieved over the concentration range 1 × 10⁻⁵ to 5 × 10⁻⁹ mol L⁻¹ tyrosine with a correlation coefficient of 0.993 and a detection limit of 2.7 × 10⁻⁹ mol L⁻¹. The developed method is simple and proceeds without practical artifacts compared to the other determination methods.