Determination of l-tyrosine by β-cyclodextrin sensitized fluorescence quenching method

A novel β-cyclodextrin (β-CD) sensitized fluorescence quenching method for the determination of l-tyrosine (l-Tyr) with Mo(VI)-phenyl-fluorone (PF) as a fluorescence probe has been developed. The fluorescence intensity of Mo(VI)-PF–β-CD was diminished as the l-tyrosine was added, the fluorescence quenching value ΔF = Fβ-CD–Mo-PF − Fβ-CD–Mo-PF–l-Tyr was enhanced in β-CD and there was a linear relationship between the ΔF and the concentration of l-Tyr. Under the optimal conditions, the linear range of calibration curve for the determination of l-tyrosine was 0.3–20.0 μg mL−1; the detection limit was 0.094 μg mL−1. NaOH (10%, w/v) is the best reagent of hydrolysis in sample preparation. The sensitized mechanism of β-cyclodextrin was discussed. The method has been applied to the determination of l-tyrosine in spirulina and food samples with satisfactory results.