儿茶酚胺铽敏化发光性质的研究及分析应用

Study on Terbium Sensitized Luminescence Properties of Catecholamine and Its Application

儿茶酚胺(Cas)作为神经递质和激素对人体的生理功能发挥着重要作用。它是一类分子中包含一个胺基和一个邻苯二酚基团的有机化合物,其中邻苯二酚基团由苯环和3,4位两个羟基组成。生理条件下,儿茶酚胺主要指多巴胺(DA)、去甲肾上腺素(NE)和肾上腺素(E)三种物质。儿茶酚胺性质不稳定,遇光或空气易氧化分解。镧系敏化发光是一种很有前途的临床和药物分析工具,在镧系敏化发光中,镧离子与有机化合物形成络合物,这些络合物具有良好的发光特性,主要用于有机分析物的测定。因此,利用镧系金属离子铽敏化发光法测定儿茶酚胺的关键是待测物与中心离子易形成稳定的络合物。儿茶酚胺与金属离子的络合作用主要依赖于分子中酚羟基解离后的氧作为成键原子,溶液的碱性越强,儿茶酚胺与金属离子的络合能力越强。在碱性介质中,为防止金属离子水解加入乙二胺四乙酸作为协同配体,金属离子铽和协同配体以及儿茶酚胺形成易溶于水的三元络合物,络合物具有良好的稳定性,并表现出较强的铽的特征荧光。加入阳离子表面活性剂十六烷基三甲基氯化铵为增敏剂,可使儿茶酚胺三元络合物体系的荧光强度增加约4~6倍。利用紫外吸收和荧光光谱研究了铽三元络合物的光物理性质以及能量转移机理,结果表明,儿茶酚胺能有效吸收紫外辐射,三元络合物荧光增强机理是配体儿茶酚胺吸收辐射能后通过分子内能量转移将能量转移给铽离子,进而产生铽的特征发射。对影响三元络合物荧光强度的主要因素如溶液酸度、试剂浓度和加入顺序、表面活性剂种类以及干扰物质等进行了讨论。在一定条件下,体系的发光强度与儿茶酚胺的浓度成线性关系。多巴胺、去甲肾上腺素和肾上腺素的线性范围分别为0.080~50.0×10^-6,0.070~50.0×10-6和0.070~50.0×10^-6 mol·L^-1;相应检出限分别为2.4×10^-8,2.2×10^-8和2.1×10^-8 mol·L^-1。建立的方法用于药物制剂中三种儿茶酚胺的定量测定,结果满意;由于反应体系所得铽络合物具有发射带窄,斯托克斯位移大,以及较长的荧光寿命等优点,该方法有望用于儿茶酚胺的自动分析、临床药代动力学研究以及相关病理的实际诊断,也可用于高效液相色谱和毛细管电泳检测器。

Catecholamines(Cas)plays an important role in physiological function of human body as neurotransmitter and hormone. They are organic compounds that contain an amine group and a catechol group that is constituted by a benzene ring with two hydroxyl groups at 3-and 4-positions.In physiological conditions,catecholamine mainly refers to dopamine(DA),norepinephrine( NE)and adrenaline(E).Catecholamines are chemically unstable,prone to spontaneous oxidation and decompose easily when exposed to light or air.Lanthanide sensitized luminescence is a promising tool for clinical analysis and drug analysis.In lanthanide sensitized luminescence,lanthanide ions form complexes with organic compounds,these chelates display a well-defined luminescence characterized,mainly for the determination of organic analytes.Therefore,the key to determining catecholamine by the terbium sensitization luminescence is that the analyte forms an effective and stable complex with the central ion. It is a general understanding that catecholamines form rather stable chelate complexes with metal ions,the two oxygen of the phenolic groups acting as donor atoms.Therefore,the more alkaline the solution,the stronger the complex ability of catecholamine and metal ions.In order to prevent hydroxide formation ethylenediaminetetracetic acid(EDTA)is added into the alkaline solutions,EDTA as synergistic ligand serves to chelate Tb3+ with high affinity and keeps it soluble in water,terbium ion and synergistic ligands and catecholamines form stable ternary complex soluble in water and exhibit strong characteristic fluorescence of terbium.The system with cationic surfactant cetyltrimethylammonium chloride(CTAC)as sensitizer,can make the luminescence for catecholamine chelates increased by a factor of 4to 6.UV absorption and fluorescent spectra were used to investigate the photophysical properties of the ternary complex and energy transfer mechanism.The study shows that the catecholamine is an effective absorber of ultraviolet radiation,and the possible mechanism of the ligand sensitized fluorescence may be explained based on intramolecular energy transfer.In the energy transfer process,the ligand catecholamine absorbs the radiation energy and transfers the energy to terbium ion through intramolecular energy transfer,thus generating characteristic emission of terbium.The main factors affecting the fluorescence intensity of ternary complex,such as solution acidity,reagent adding concentration and sequence,types of surfactants and interfering substances,etc.,were discussed.Under the optimized condition, the luminescence intensity of the system is linearly related to the concentration of the catecholamines.Linearity is observed in the concentration ranges of 0.080~50.0×10^-6 mol·L^-1 for dopamine,0.070~50.0×10^-6 mol·L^-1 for norepinephrine,and 0.070~50.0×10^-6 mol·L^-1 for epinephrine,with limits of detection as low as 2.4×10^-8,2.2×10^-8 and 2.1×10^-8 mol· L^-1,respectively.The proposed method has been successfully applied to the quantitative determination of the three catecholamines in a pharmaceutical preparation.Due to the advantages of narrow emission bands,large stokes shift and long excitedstate lifetimes,it will be possible to investigate this method further for automated analysis,clinical pharmacokinetics study, practical diagnostic for catecholamine-related pathologies,and it can be used in HPLC and CE detectors.