Determination of tyrosine by sodium fluorescein-enhanced ABEI–H₂O₂–horseradish peroxidase chemiluminescence

In this study, N-(4-aminobutyl)-N-ethylisoluminol (ABEI) was used as an energy donor, while sodium fluorescein was used as an enhancer and energy acceptor, which resulted in it producing resonance energy transfer and greatly increasing the strength of chemiluminiscence (CL). When horseradish peroxidase (HRP) is added, hydrogen peroxide (H₂O₂) will quickly separate into hydroxyl radicals (·OH) and superoxide ions (O₂·⁻). If tyrosine (Tyr) is present in the system, the hydroxyl group on the benzene ring of Tyr robs ·OH and O₂·⁻ in the CL system, thereby reducing the intensity of CL. Based on this phenomenon, a luminescence system of ABEI and sodium fluorescein system was established to detect Tyr for the first time. This method has an ultra-low detection limit and a wide linear range, and is cheap and easy to operate. Under various optimal conditions, the linear range is from 3.0×10⁻⁸ to 3.0×10⁻⁵ mol/L, and the limit of detection is 2.4×10⁻⁸ mol/L. It has been successfully used in the detection of dairy products with satisfactory results.