▎ 摘　　要

NOVELTY - Reagent comprises a solution of the dopamine functionalized nitrogen-doped graphene quantum dot with off-open function, where the dopamine-functionalized nitrogen-doped graphene quantum dots with off-on function are prepared by adding catalyst N-hydroxysuccinimide and 1-(3-dimethylaminopropyl)-3-ethyl carbon diacetate to the nitrogen-doped graphene quantum dot aqueous solution with a concentration of 0.05-10mg/mL. The mixture of imine hydrochloride, after activation for 5 minutes-1 hour, added the aqueous solution of dopamine dropwise, heated in a water bath at 35-60℃ for 1-8 hours, and stirred in the dark for 5-48 hours. The obtained product is dialyzed for 3-72 hours with a dialysis bag with a molecular weight of 1000 Dalton to obtain a product. USE - Reagent used for trivalent chromium ion or valine detection which is used in food, medicine, feed and cosmetic. ADVANTAGE - The reagent has selectivity of chromium ion and valine, high sensitivity, simple technique, convenient operation, strong practicability and wide application prospect. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following: 1. a method for detecting trivalent chromium ions, which involves: adding the substance to be tested of 5.0*10-3 M, adopting the fluorescence photometry to test, test solution is in EM 315 nm and EM 440nm Fluorescence Spectroscopy; and 2. a method for detecting valine, which involves: using complex solution that the reagent that for detecting trivalent chromium ion or valine, adding 5.0*10-3 M of the substance to be tested, and using fluorescence photometry to test the fluorescence spectrum of the test solution at EM 315 nm and EM 440 nm.