萘甲酸盐类离子液体对β-双酮类抗生素配合物的强荧光增敏机理与分析应用

Beta-diketone antibiotics (DKAs) are novel "pseudo-persistent" environmental pollutants due to their wide and frequent application. However, the fluorescence intensities of DKAs can not satisfy the requirement for their trace analyses, and thus the strong fluorescence sensitizer are often used to enhance DKAs fluorescence intensity. During the previous project funded by NSFC, we found that novel naphthoate ionic liquids had strongly fluorescence-enhancing effects on Eu3+-DKA complex. So far, the reported relevant mechanisms are contradictory on their interaction between ionic liquids and Eu3+-DKA complex. This proposal aims to elucidate the mechanism on the strongly fluorescence-enhancing effects of naphthoate ionic liquids by means of the following researches: (1) A series of novel imidazolium naphthoate ionic liquids will be synthesized and characterized; (2) The ligand energy distribution effects of ionic liquids and DKAs on fluorescence behavior of complex will be probed; (3) TICT probe such as Nile Red will be used to illustrate the change of microenvironment in complex system due to the presence of ionic liquids. The special solvent effects of ionic liquids will be investigated according to the change of Stokes shift. Combined with other parameters of fluorescence theory, we infer the possible mechanisms on the strongly fluorescence-enhancing effects of naphthoate ionic liquids; (4) The highly sensitive fluorescent determining method for DKAs will be developed by introducing the novel ionic liquids into post-column reaction system of high performance liquid chromatography, and it can satisfy the requirement of DKAs, at trace levels, muti-residual analysis for ordinary laboratories. This study can lay theoretical foundation for developing novel ionic liquids possessing strongly fluorescence-enhancing effects, and can further promote wide application of ionic liquids in "green" analytical chemical fields. Therefore, this proposal possesses a good theoretical meaning and practical application value.

大量而频繁使用的β-双酮类抗生素（DKAs）成为新型"假持久性"环境污染物，利用强荧光增敏效应提高其痕量检测水平仍是亟待解决的科学问题。申请人在前一个国家基金的研究中发现：新型萘甲酸盐类离子液体对Eu3+-DKA配合物具强荧光增敏效应，但国内外有关离子液体对配合物增敏或猝灭效应的机理解释存在相悖。本项目首先进行系列咪唑萘甲酸盐类离子液体的合成；探讨离子液体和DKAs两级配体能级分布对配合物荧光性能的影响；并以尼罗红等典型TICT（分子内扭转电荷转移）探针为手段，利用TICT理论解释离子液体对配合物体系的微环境影响；以Stokes位移的大小分析离子液体的特殊溶剂效应；结合其它参数的变化，综合解析强增敏效应产生的机理；基于上述强增敏效应，建立环境中痕量DKAs的高灵敏荧光检测技术。该研究能为今后研发具强增敏效应离子液体提供一定的前期理论基础，并将进一步推进离子液体在绿色分析技术领域的广泛应用。

喹诺酮与四环素类抗生素因其分子结构均含有β-双酮功能基团，故被称为β-双酮类抗生素（DKAs），它们的荧光检测是一种较为直接和灵敏的测试手段。由于多数品种为弱荧光，常将其与稀土Eu3+反应形成荧光配合物（Eu-DKAs），利用Eu3+的灵敏特征荧光检测DKAs残留。但现有技术仍难满足痕量分析(ng/L-pg/L)的灵敏度要求，故开发荧光增敏剂已成为该技术突破的关键问题。根据国家基金（21377100）合同内容，课题组开展了系列萘甲酸盐类离子液体合成及其相关功能研究，获得的结论如下：.（1）运用三步合成法，以N-甲基咪唑、氯代烷、1-萘甲酸为原料合成了系列咪唑萘甲酸盐离子液体[CnMIM][NPA](n=4, 5, 6)，并运用核磁、红外和质谱等仪器进行了表征。通过控制变量法，改变反应体系的溶剂，反应的时间及配比，对各种合成参数进行了优化。1-萘甲酸钠与氯代3-甲基咪唑反应时，在投料比为1:1，反应温度为80℃，反应24h的条件下产率最高，反应最完全。.（2）[CnMIM][NPA]对弱荧光污染物如酚类雌激素、β-双酮类抗生素等具有较强的荧光增敏效应，故可作为弱荧光物质的荧光增敏剂，应用于行业性污染物的灵敏光谱分析。此外，该离子液体也具有强酸性和亲水性，这些性质可应用于各种微萃取体系中，作为萃取剂或分散剂使用，扩展了离子液体的深度应用。. （3）研究了[C4MIM][NPA]对Eu3+和Eu3+-NFLX配合物的荧光影响。[C4MIM][NPA]具有强分子荧光，其对Eu3+和Eu3+-NFLX配合物均具强增敏效应，并伴有Eu3 +的荧光寿命增加现象；Eu3+-NFLX配合物的最佳pH为6.5，二者的配位比为1:5。.（4） 开发了基于[C4MIM][NPA]的“无有机溶剂微萃取”技术。[C4MIM][NPA]被作为分散剂单独使用，与以往单独使用[Cnmim][BF4]作为分散剂相比具有如下优点：扩大了水溶液的非极性环境，导致了提取剂沉淀体积的增加，提高了整体实验的回收率；呈现强酸性，不同比例的混合可调节pH范围，故减少了pH调节步骤。该技术应用于分析水样、血样、尿样、牛奶、蜂蜜等基质中的三氯生、甲基三氯生和四环素等污染物均取得了较低的检出限和较高的重现性。由于整个操作过程没有使用任何有机溶剂，实现了整个全处理过程更加绿色和环保化。