Studies On The Electrochemical Sensor For Methyl Parathion

Chemically modified electrode is an active research area in electroanalytical chemistry. The attractive characteristic of the modified electrode is that its function can be achieved by modified the electrode surface at molecular level.The modification makes the electrode possess many functions such as enrichment, separation and selectivity for the determination. Thus, chemically modified electrode attracted much attention and possesses attractive prospects in analytical chemistry. In this work, we developed several electrochemical sensors for parathion-methyl. The main contents of this work were proposed as following:1. Mesoporous silica (Meso-SiO2) was synthesized using cetyltrimethylammonium bromide (CTAB) as the template under alkaline atmosphere. After that, a mesoporous SiO2-modified carbon paste electrode was fabricated, the electrochemical properties of the modified electrode were characterized using K3[Fe(CN)6] as electrochemical probes. Compared to the unmodified electrode, it was found that the redox peak current of K3[Fe(CN)6] was significantly enhanced at the modified electrode. Electrochemical behaviors of methyl-parathion at the modified electrodes were investigated by cyclic voltammetry and square wave voltammetry. The results indicate that the modified electrode can improve the current response of methyl parathion. The effects of the electrolyte, preconcentration time, accumulation potential, pH value, mesoporous silica dosage, scanning rate and other conditions on the oxidation peak current was investigated. Under the optimal conditions, a good linear relationship between the current response and methyl-parathion concentration was obtained from1.0×10-5mol·L-1to1.0×10-7mol·L-1with the equation of Ip (μA)=1.885c(μmol·L-1)+0.1247(R=0.991) and a detection limit of6.0×10-8mol·L-1(S/N=3).2. A novel electrochemical sensor was fabricated with electrochemical polymerization of L-lysine onto the glassy carbon electrode (GCE) surface. The electrochemical properties of poly-L-lysine modified electrode was investigated using K3[Fe(CN)6] as probes. The results indicates that the redox peak current at the L-lysine modified glassy carbon electrode was significantly enhanced. Electrochemical behaviors of methyl-parathion on the modified electrodes were investigated thoroughly. The results indicated that poly-L-lysine film modified glass carbon electrodes can improve the current response of methyl-parathion. The effects of electrolyte, accumulation time, accumulation potential, pH value and scan rate were optimized. Under the optimal conditions, the oxidation peak current of methyl-parathion is linearly releated to its concentration in the range from1.0×10-6mol·L-1to1.0×10-4mol·L-1, the linear equation is Ip(μA)=0.4796c(μmol·L-1)+39.313(R=0.993) and the detection limit is4.0×10-7mol·L-1(S/N=3). Finally, the modified film electrode was successfully applied to determine methyl parathion in real samples.3. A poly-2-Mercapto-5-methyl-1,3,4-thiadiazde film modified glassy carbon electrode (p-AMT/GCE) was fabricated by using cyclic voltammetric scanning in the potential range from-0.2V to+1.7V. Electrochemical behaviors of methyl-parathion at the modified electrodes were investigated with cyclic voltammetry and square wave voltammetry, the results indicate that the modified electrode shows catalytic effect on the electrochemical reaction of methyl parathion. Compared to the unmodified glassy carbon electrode, the oxidation peak potential of methyl-parathion shifted negatively about40mV and the oxidation peak current significantly increased. Under the optimal conditions, the oxidation peak current is proportional to methyl-parathion concentration in the range from7.0×10-8mol·L-1tol.0×10-5mol·L-1with a equation of Ip (μA)=3.918c(μmol·L-1)+4.4550(R=0.994) and a detection limit of4.8×10-8mol·L-1.