关键词: 电化学检测, 循环伏安, 方波伏安, 荧光光谱, 氨, 荧光胺

Abstract: Fluorescamine is a non-fluorescent reagent widely used for the quantitative determination of primary amines by fluorescence spectroscopy as it reacts readily with primary amines to form a fluorescent product. In this work, a new sensitive voltammetric method for the detection of ammonia in aqueous solution by the reaction with fluorescamine has been developed. First, the electrochemical behaviour of fluorescamine in the absence and presence of ammonia was investigated in 0.1 mol L^-1 borate buffer solution (pH 9.0) by cyclic voltammetry using a glassy carbon (GC) electrode. As for fluorescamine itself, a well-defined irreversible oxidation peak could be observed at ca. 0.70 V vs. SCE. When ammonia was added to the fluorescamine solution, another irreversible oxditaion peak corresponding to the oxidation of the reaction product formed between fluorescamine and ammonia could be observed at ca. 0.46 V vs. SCE. Upon the addition of ammonia, the oxidation peak of fluorescamine became smaller while the oxidation peak of the reaction product formed increased in height, due to the stoichiometric chemical consumption of fluorescamine by ammonia and the formation of the product during the reaction, respectively. These two anodic peaks corresponding to the oxidation of fluorescamine and its fluorescent product formed were then used for the quantitative detection of ammonia, explored by square wave voltammetry and by fluorescence spectroscopy. The square wave voltammetric response of the reaction product formed showed a linear response over ammonia concentration range of 0 to 60 μmol L^-1. The limits of detection (LOD) was found to be 0.71 μmol L^-1 and 3.17 μmol L^-1 determined based upon Signal/Noise (S/N) = 3 and 3σ, respectively. These limits of detection are similar to those obtained with the fluorometric method.

Key words: electrochemical detection, cyclic voltammetry, square wave voltammetry, fluorescence spectroscopy, ammonia, fluorescamine