Preconcentration and spectrofluorometric determination of L-tryptophan in the presence of D-tryptophan using a chiral magnetic nanoselector

In this study, a synthetic chiral magnetic nanoselector was prepared by immobilizing bovine hemoglobin on modified silica coated magnetic nanospheres. The functionalized magnetic nanospheres had a core-shell structure, with an average diameter of 65 nm. The properties of the produced nanospheres were characterized by X-ray diffraction, FT-IR and transmission electron microscopy. The prepared nanospheres were used for determination of L-tryptophan in presence of D-tryptophan. The basis of method was on enantioselectivity of immobilized hemoglobin on magnetite surface. Furthermore, the enantioselselectivity site of hemoglobin confirmed by molecular modeling method. The results showed that the optimum pH for the analyte adsorption was 7.0. The adsorbed amino acid was then desorbed with acetonitrile/HCl (1:1) and determined with spectrofluorometric method at 358.0 nm wavelength. The calibration curve was linear in the range of 0.50-33.00 ng mL(-1) of L-tryptophan with a detection limit of 0.01 ng mL(-1). Furthermore, the prepared nanospheres have been employed for the determination of L-tryptophan in urine samples. (C) 2015 Elsevier B.V. All rights reserved.