在亚硝酸盐存在下钴(Ⅱ)-中性红络合物的极谱催化波的性质

Behavior of the Polarographic-Catalytic Wave of the Complex Between Cobalt(Ⅱ) and Neutral Red in the Presence of Nitrite

在0.2 mol·L^-1的氨水-NH4Cl（pH 9.5）缓冲溶液中,1.0 mol·L^-1NaNO2存在下,钴（Ⅱ）-中性红（NR）络合物于-1.19 V（νs.SCE）处产生灵敏的极谱波,二阶导数波峰电流与钴浓度在2.0×10^-8～5.0×10^-5molL-1范围内呈线性关系,检出限为1.0×10^-8mol·L^-1.研究了钴（Ⅱ）-中性红（NR）络合物的电极反应机理,证明了该波为不可逆极谱催化波,测得电活性络合物组成为钴（Ⅱ）：（NR）=1：1.电活性络合物的中心离子钴（Ⅱ）还原,电子转移数n=2.该方法用于维生素B12注射液和天然水中痕量钴的测定,测得分析结果的RSD（n=6）值均小于0.7%,回收率在98%至101%之间.

In an ammoniacal buffer solution of pH 9. 5, and in the presence of 1.0 mol · L^-1 NaNO2 solution, a sensitive catalytic polarographic wave of the complex formed by Co（ Ⅱ ） and neutral red （Co-NR） was observed at -1. 19 V （vs. SCE）. Linear relationship between the 2nd derivative of peak current and the concentration of Co（ Ⅱ ） was obtained in the range of 2. 0× 10^-8 -5. 0× 10^-5mol · L^-1 of Co（ Ⅱ ）, with a detection limit of 1.0× 10^-5mol · L^-1. Results of test for the composition of the complex Co-NR showed that the mole ratio between Co ion and NR was 1 to 1. As shown by the results of cyclic voltarnmetric study and studies by some other electrochemical methods, on the property of the polarographic wave and the mechanism of the electrode reaction, the polarographic wave was proved to be of catalytic and adsorptive behavior and was an irreversible process. The peak current was produced by reduction of cobalt ion in the Co-NR complex, and the number of electron transfer of 2 was involved in the electrode reaction. In its application to the determination of cobalt in samples of VB12 injection and natural water, RSD＇s （n=6） less than 0. 7% were obtained, and recoveries found were in the range of 98%-101%.