New Fluorescent Systems With High Sensitivity And Selectivity And Their Applications

As one of the fluorescent analytical methods, fluorescent probe technology can realize the qualitative or quantitative detection of analyte through the specific recognition of recognition groups in fluorescent probe to target objects. The technology has received considerable attention and been widely used in the field of biological science, clinical medicine and analytical chemistry owning to the simplicity and sensitivity. Hence, it is of great interest to develop new fluorescent probes with high sensitivity and selectivity, and apply them to assay pharmaceutical and biological samples. In this thesis, the aim is to develop new fluorescent probe systems. Subsequently, we propose novel methods for determination of adenine and guanine, respectively. Additionally, a new fluorescent method for determination of ampicillin is established based on carbon nanodots as catalyst. The main contents studied are as follows:A novel fluorometric method for the determination of adenine was proposed, based on the fluorescence quenching of a nuclear fast red-silver complex as a small molecule optical probe. The characteristic spectra of absorption, resonance Rayleigh scattering and fluorescence of the system were analyzed. Adenine, Ag+ and nuclear fast red formed a sandwich-type complex. The composition of compound and the mechanisms of fluorescence quenching were discussed. The optimal conditions for reaction and the effects of co-existing substances were also investigated. The quenched fluorescence intensity was proportional to the concentration of adenine in the range of 0.03~0.90 μg/m L, with the limit of detection of 0.023 μg/m L. The method was applied satisfactorily to the determination of adenine in synthetic samples, DNA, human sera and vitamin B4 tablets with recoveries from 95.3 % to 105 %.A novel fluorescence method for the determination of guanine was developed based on the fluorescence enhancement of Cu2+-nuclear fast red complex in Tris-HCl buffer. The complex of Cu2+ with nuclear fast red resulted in a dramatic quenching of the fluorescence intensity. Nuclear fast red were dissociated from the complex with the addition of guanine due to the strong interaction between guanine and Cu2+, which caused the fluorescence enhancement. The enhanced fluorescence intensity was well proportional to the concentration of guanine in the range of 0.0075~0.165 μg/m L with the limit of detection 2.9×10-3 μg/m L. The method has been applied successfully to the determination of guanine in serum and DNA samples, and the recoveries were from 96.0% to 104.8%.In the weak acid buffer medium, Cu2+ could react with guanine to form a 1:1 coordination compound, which only resulted in minor change of the fluorescence intensity. Then, this compound quenches dramatically the fluorescence of eosin Y. The quenched fluorescence intensity was well proportional to the concentration of guanine in the range of 0.50~17.5 ng/m L with the limit of detection 0.23 ng/m L. The characteristics of absorption and fluorescence spectra were analyzed to investigate the interaction of the system, and the structure of the ternary complex was speculated. Meanwhile, we discussed the fluorescence quenching mechanism of eosin Y by Cu2+, guanine and Cu2+-guanine. The optimum conditions of the reaction and the effect of coexisting substances were also researched. The method has been applied satisfactorily to the determination of guanine in DNA and urine samples with the recoveries from 98.7% to 104.6%.A novel fluorescence method for the rapid determination of ampicillin was established based on the catalyze degradation of ampicillin by carbon nanodots. The optimum conditions of reaction and the effects of coexisting substances were investigated. Under the optimum experimental conditions, the enhanced fluorescence intensity was well proportional to the concentration of ampicillin in the range of 0.1~15 μg/m L with the limit of detection 8.3×10-9 g/m L. The method has been applied successfully to the determination of ampicillin in capsules and serum samples with satisfactory recovery.