Study Of New Method For Rapid Detention Of Thiol Compounds

Thiol compounds play an indispensable role in medical health and scientific research, thus the detection of those compounds become more and more important in analytical chemistry. Many methods have been developed to detect thiol compounds. Among those methods, the fluorescence methods have become one of the best choices for the detection of thiol compounds because of its low cost, high selectivity, high sensitivity and various kinds of fluorescent probes. While, the detection of thiol compounds using fluorescence methods is time-consuming because the synthesis and separation of organic fluorescent probes requiring many steps and the reactions between these probes and thiol compounds are relatively slow. So, new methods for rapid detection of thiol compounds should be developed. In this thesis, two methods have been developed to detect thiol compounds rapidly.The first idea is to search for a commercial fluorescent probe which can directly and rapidly respond to thiol compounds. In the experiment, the fluorescence of fluorescein isothiocyanate (FITC) could quenched by thiol compounds rapidly. Thus, a novel method for rapid detection of thiol compounds was established using FITC as fluorescence probe. Thiol compounds could be detected in 5 minutes at the optimized conditions including pH and reaction time. The method was used to detect glutathione (GSH) in real samples and showed good selectivity and recovery. The limits of detection (LOD) were 3.08μM for glutathione (GSH),2.66μM for homocysteine (Hcy),1.28μM for cysteine (Cys), and 1.92μM for dithiothreitol (DTT).The second idea is to select a fluorescent probe that can be rapidly synthesized and respond to thiol compounds rapidly. Based on the previous work of our group and literature research, copper nano cluster (Cu-NCs) is a kind of excellent fluorescent probe which can be rapidly synthesized and respond to thiol compounds quickly. It also has the advantages of low cost compared with gold nanoparticles and silver clusters. Cu-NCs were successfully synthesized in 10 minutes using single stranded DNA as template. The conditions for Cu-NCs synthesis such as the base number of poly thymine, solution pH, reaction time, molar ratio of sodium ascorbate and Cu2+, and molar ratio of poly thymine and Cu2+ were optimized. The detection of thiol compounds was based on the fluorescence quenching of copper nanoclusters by thiol compounds. Thiol compounds could form non-fluorescent coordination complex with copper nanoclusters. Under the optimized conditions, the linear range of detection for dithiothreitol, cysteine, homocysteine and glutathione are 0.50uM to 25.00 uM, 0.50uM to 30.00 uM,1.50uM to 32.50 uM and 0.50uM to 30.00 uM respectively. Using this method, glutathione in glutathione capsules was determined with good selectivity and recovery.