Determination Of Mercury Ions Online With Rhodamine6G By Fluorescence Quenching Method

In recent years, heavy metal and other toxic substances pollution cause a lot of waterpollution accidents, especially mercury, chromium, cadmium, arsenic, lead contaminationhas become increasingly prominent. Heavy metal has hidden, long-term and cumulativeproperties, even a very small amount may result in serious consequences, harm people’shealth. Therefore, heavy metal pollution has attracted wide attention. The traditional heavymetal ions detection methods which due to large equipment, long measurement period andhigh cost, the need for complex pre-processing and generally stay in the laboratory stage,increasingly unable to meet the need of environment monitoring department. Therefore,the study of fluorescent reagent to detect heavy metal ions, to build a simple and fast, highsensitivity, high selectivity detection method, and to achieve real-time detection, on-line,in situ, and automation has a very important scientific significance and application valueundoubtedly.The main work of this paper is based on the basic principles of fluorescencespectroscopy, and to establish a basic experimental program of detecting Hg2+ions withRhodamine6G by fluorescence quenching method, and use the basic principles of theprogram for detecting of other heavy metal ions. On this basis, we investigate the effect ofthe combined two or more heavy metal ions to the fluorescence intensity of Rhodamine6G.Finally, the study attempts to apply the results of this research to develop heavy metal ionson-line monitoring instrument for achieving rapid, automated and real-time continuouson-line monitoring of single or multiple heavy metal ions in water environment. In thispaper, as part of the research, has obtained the following conclusions:1) Determining the good fluorescent chromophore of the fluorescence quenchingmethod detecting heavy metal ions is Rhodamine6G, the maximum excitation wavelengthand emission wavelength is526nm/554nm respectively. There is a good linear relationshipbetween the fluorescence intensity and Hg2+ions concentration in the range of5×10-7mol/L~6×10-6mol/L. With further increasing in concentration, the fluorescenceintensity did not increase, on the contrary, appears decline phenomenon.2) In different solvents and pH, the fluorescence intensity of rhodamine6G solutionis different. Experimental study results show that the fluorescence intensity of rhodamine6G in ethanol, water, sodium hydroxide(0.5mol/L), nitrate(0.75mol/L) four solventsfluorescence intensity from strong to weak as follows: ethanol> water> nitrate> sodium hydroxide. Rhodamine6G fluorescence intensity decrease with increasing ofOH-concentration and also has weak with increasing of H+concentration in different pHsolution.3) Establishing the optimal experimental conditions for determination of mercury ionswith rhodamine6G by fluorescence quenching method. Of which reagents are added inthe order as Hg2+, KI-VC, PVA-124and Rh6G; The reaction time is measured out10minto1hour after all the reagents are added; The concentration of Rh6G is5×10-5mol/L,with amount of5mL; KI-VC was added with amount of4mL; PVA-124was added withamount of8mL.4) Drawing the regression curve of determination of Hg2+with Rhodamine6G byfluorescence quenching method. Get Hg2+concentration and fluorescence quenching valuesystem showed a good linear correlation in the range of8~100ug/L. The regressionequation is△F=1.8267C+2.6,the correlation coefficient is R2=0.9963. Precision andrecovery tests performed on the test solution with different concentrations of Hg2+,obtaining the relative standard deviations between2.3%to3.8%and the recoveriesbetween97.5%and102%. It shows the method has good precision and accuracy. Themeasurement results coincide with the actual amount for the determination of watersamples in laboratory, quite satisfactory.