间对硝基苯酚异构体的电化学测定及取代机理研究

制备了单壁碳纳米管修饰玻碳电极(SWCNT/GCE),采用伏安法研究了间、对硝基苯酚异构体在修饰电极上的电化学行为,分别观察到间硝基苯酚(m-NP)和对硝基苯酚(p-NP)的准可逆氧化还原峰,两物质氧化峰电位差为0.192V,说明间、对硝基苯酚异构体可在SWCNT修饰电极上同时测定.采用线性扫描伏安法优化了硝基苯酚同分异构体电化学响应条件.优化条件下,m-NP在浓度2.7×10~(-6)~1.0×10~(-4)mol/L范围内,其峰电流(Ip)和浓度呈线性关系;p-NP在浓度2.0×10~(-6)~1.0×10~(-4)mol/L范围内,Ip和浓度呈线性关系.两者的Ip都与扫速(v)成线性关系,这说明它们在修饰电极上的电化学过程均与吸附传质有关,电极过程是受吸附控制.基于Nicholson方法,获得m-NP和p-NP的电极反应速率常数(kS),并用Hammett方程计算出Hammett反应取代常数ρ.

Determination of Nitrophenols Isomers and Substitution Mechanism

Single walled carbon nanotubes(SWCNT) modified glassy carbon electrode(SWCNT GCE) was fabricated.The electrochemical behavior of nitrophenols isomers at SWCNT GCE was investigated by Cyclic Voltammetry(CV).Two pairs of quasi-reversible redox peaks for m-nitrophenol(m-NP) and p-nitrophenol(p-NP) were observed.The potential difference of the oxidation peaks for nitrophenols isomers was 0.19 V,indicating that the simultaneous determination of m-NP and p-NP at this SWCNT GCE was feasible.The effect factors of the electrochemical response of nitrophenols isomers were optimized by linear sweep voltammetry(LSV).Under the optimum conditions,two linear calibration plots of the peak current and their concentration for m-NP and p-NP were obtained in the range of 2.7×10~6-1.0×10~4mol/L and 2.0×10~6-1.0×10~4mol/L,respectively.Their oxidation peaks current increased direct proportionally with the scanning speed,which suggested that the electrochemical oxidation of nitrophenols isomers was adsorption-controlled process.Based on Nicholson method,the rate constant of electrode reaction could be estimated,concurrently,and the substitution constant(ρ) of Hammett reaction was calculated by using Hammett equation.