Investigations On The Fluorescence Properties Of Ionic Liquids And Its Application In Hemoglobin Quantification

Ionic liquids (ILs) have been widely uesd in various fields, e.g., analytical chemistry, environmental and material science, due to their unique physical and chemical properties. The investigations on the spectral properties of ILs can provide useful information of its structure and related molecular interactions, which offer theoretical basis for the extension for the application fields of ILs. In the present thesis, we present the preliminary results for investigating the spectral properties of imidazole ILs, and based on which a new quantitative method for hemoglobin determination is developed using IL as the fluorescent probe.In chapter 1, we discussed the classification of ionic liquids and their properties, as well as the current status of research on the spectral properties of ionic liquids. In addition, the quantitative methods used for hemoglobin determination are also briefly reviewed.In chapter 2, we investigated the spectral properties of halogenated imidazole ILs with symmetric structure. Meanwhile, we have studied the effect of molecular structure and environmental factors on the spectral properties of ionic liquid. The experimental results indicated that the reduction of electronegativity of the anionic moiety of ILs and the increase of the length of alkyl chain of imidazole cation lead to the enhancement of the absorbance of ILs. However, these changes in the structure of ILs contribute oppositely to the fluorescence of the ILs, i.e., the reduction of electronegativity of the anion leads to the decrease of the fluorescence while the increase of alkyl chain length results in a fluorescence enhancement. At the same time, the fluorescence response of ILs shows selectivity to different surfactant. Among the tested ILs,1,3-dibutyl imidazole chloride salt (BBimCl) is found to give most intense fluorescence with a quantum yield of 0.4836.In chapter 3, a new quantitative method for the determination of hemoglobin is developed based on its enhancement effect on the fluorescence of 1,3-dioctyl imidazole bromine salt (OOimBr). In aqueous medium, OOimBr gives rise to weak fluorescence, which can be significantly enhanced by the addition of Hb and a linear relationship is obtained between the fluorescence enhancement and Hb concentration within a certain concentration range. The linear range for Hb quantification is 0.03～1.0 μmol L-1. The limit of detection is derived to be 0.008 umol L-1, along with a RSD of 2.0%(0.5 μmol L-1,n=11). The developed quantitative protocol is applied successfully to the determination of Hb concent in whole blood sample with spiking recoveries between 96% and 100%.