β-环糊精用于L-苯丙氨酸的二次微分简易示波伏安测定

Use of β-Cyclodextrin in the 2nd Derivative Simple Oscillovoltammetric Determination of L-Phenylalanine

在0．2mol·L^-1NaOH底液中，β-环糊精在二次微分简易示波伏安图上-0．38V处产生一可逆峰，阴极支的峰高随L-苯丙氨酸与β-环糊精形成的包结物量的增加而降低。根据β-环糊精的示波特性，建立了L-苯丙氨酸含量测定的二次微分简易示波伏安法。试验结果表明：β-环糊精在二次微分简易示波伏安图上的峰高与L-苯丙氨酸浓度在2．5×10^-6～4．5×10^-5mol·L^-1范围内呈线性关系，相关系数为0．9996，检出限为1．0×10^-6mol·L^-1。对于8．0×10mol·L^-1L-苯丙氨酸5次测定的RSD为3．1％，平均回收率为100．0％。测得β-环糊精与L-苯丙氨酸形成 包结物的包结比为1：1，包结常数为1．9×10^6。

In the base solution of 0. 2 mol · L^-1 NaOH, a reversible peak produced by β-cyclodextrin （β-CD） was found in the 2nd derivative oscillovoltammogram at -0. 38 V （vs. SCE）; and the peak height of cathodic branch was found to decrease with the increase of concentration of the inclusive complex formed between β-CD and L-phenylalanine. A linear relationship between the peak height and concentration of L-phenylalanine was found in the range of 2. 5×10^-6-4. 5×10^-5mol · L^-1 （r=0. 999 6）, with a detection limit of 1.0×10^-6mol·L^-1. Based on this feature, a method of 2nd derivative oscillovoltammetric determination of L-phenylalanine was proposed. Test of precision was made with 5 determinations of L-phenylalanine at the concentration level of 8. 0 × 10^-5 mol·L^-1 , giving the value of RSD of 3. 1%. Results of recovery test were obtained with an average of 100. 0%. Molar ratio of the inclusive complex formed between β-CD and L-phenylalanine was found to be 1 to 1 and the complex formation constant was 1.9 × 10^6.