| Heavy metal ions (such as mereury, cadmium, lead, arsenie, chromium, etc.) are teratogenic and carcinogenic pollutants. Their nonbiodegradable nature and ability to persist for long periods in the river, soil and biome make them bio-accumulative and toxic. Through the food chain, they can affect human and animal health. Therefore, it is necessary to develop sensitive, rapid and simple methods for the determination of heavy metals.Ionic liquids (ILs) are liquid electrolytes composed entirely of ions. Low toxicity, high chemical and thermal stability, almost negligible vapor pressure, high conductivity and wide electrochemical potential windows make ionic liquids suitable for many applications in the elctrochemical area. In this paper, several electrochemical sensors based on ILs composites have been developed, and have been successfully applied to the determination of heavy metal ions such as Cd(II) and Pb(II). These results extended the applications of ILs in electroanalytical chemistry and the main content of this thesis includes:(1) Titanium silicalite-1 (TS-1), combinating with ionic liquids (ILs), was used to construct the TS-1/ILs composite film modified glassy carbon electrode (GCE). Then an enhanced electrochemical sensing platform to determine Cd (II) was fabricated by using linear sweep voltammetry (LSV). The electrochemical properties of the composite film modified glassy carbon electrode were investigated. It is found that the prepared TS-1/ILs composite film exhibited improved sensitivity for the Cd (II) detections. Following the optimization of the experimental parameters, the linear calibration curves ranged from 6.80×10-8 to 1.63×10-5 mol/L (R = 0.998) and the detection limit (at S/N = 3) was estimated to be around 1.0×10-9 mol/L. Finally the method was successfully applied to determine Cd (II) in water samples.(2) A composite film of thiol-functionalized mesoporous molecule sieve (P123-SH) and ionic liquids is introduced for fabricating a voltammetric electrochemical sensor for Cd (II). The chemically modified electrode exhibits excellent sensitivity towards Cd (II) in presenting a markedly increased stripping peak current. Under the optimized experimental parameters, a linear response is obtained in the concentration range from 2.9×10-8 to 8.7×10-4 mol/L of Cd (II). The detection limit is as low as 1.0×10-9 mol/L (at S/N = 3) after an accumulation at -1.1 V for 4 min. The method was successfully applied to determine Cd(II) in water samples. Features such as large electroactive area, fast electron transfer and low background current make this composite film modified electrode a promising platform for fabricating reliable electrochemical sensors for various species, such as heavy metal and environmental pollutants.(3) A novel and sensitive electrochemical method was developed for the determination of Cd (II) based on a acetylene black (AB) and ionic liquids composite film modified electrode by using linear sweep stripping voltammetry. Experimental results showed that the AB/ILs composite film coated GCE could greatly improve the sensitivity of determining cadmium. Under the optimized conditions, the linear range is found to be 1.5×10-8 to 7.7×10-5 mol/L, with the detection limit of 1.0×10-8 mol/L. Finally the method was successfully applied to determine Cd(II) in water samples.(4) Acetylene blackand ionic liquids composite film modified electrode was prepared for the determination of Pb(II) by linear sweep stripping voltammetry. Experimental results showed that the sensitivity of determining cadmium was greatly improved at the AB/ILs composite film coated GCE . Under the optimized conditions, the linear range is found to be 2.8×10-8 to 2.5×10-5 mol/L, with the detection limit of 1.0×10-9 mol/L. Finally, this sensor was successfully used to detect Pb(II) in water sample. |
PDF Full Text Request