【摘要】 在含EDTA、溴代苯羟乙酸（Br-BHA）的硫-磷混酸介质中,变价元素,钼（VI）-钨（VI）-Br-BHA络合物分别产生不太灵敏的极谱电流。加入NaClO₃后,产生灵敏催化电流[比在苯羟乙酸（BHA）体系分别增敏2.3倍和3倍],峰电位（Ep）分别移至-0.44V和-0.78V。系统研究了10余种易质子化有机染料和8种阳离子表面活性剂对上述催化电流进一步增敏效应,其中以亚甲蓝（MB）为最佳。无NaClO₃时,加入MB,原络合电流略有所降低,E_D无明显变化。但当加入NaClO₃后,极谱催化电流得到进一步增敏,Ep分别为-0.43V和-0.83V。钼（VI）、钨（VI）测定的线性范围分别为2×10^-9～4×10^-7和5×10^-10～2×10^-8mlo/L,检出限分别为1×10^-9和3×10^-10mol/L。大多共存离子（阳离子44种,阴离子10种）不干扰测定,[Mo（VI）]:[W（VI）]或反之,为1:25000互不干扰。方法已用于合金、纯铁等样品中钼、钨的同时直接测定,结果满意。文中对络合物组分比、电流特性、电极反应机理、增敏可能的规律和机理等进行了详细的研究,并计算了一系列有关常数和参、函数。更多还原

【Abstract】 Some variable valence elements ,such as molybdenum and tungsten ,in the medium of sur- furic acid and phosphoric acid (S-P) mixtured in 1 + 1,containing p-bromo benzene hydroxyacetic acid (Br-BHA ),EDTA, appeared the polarographic currents which were not so sensitive .But in the presence of NaClO3,the very sensitive catalytic current observed at -0. 44V[for Mo(Ⅵ)]and -0. 78V [for W(Ⅵ)]respectively. A possibility of these catalytic currents mentioned above further enhanced by protonated organic dyes or by cationic surfactants has been investigated. Among them the methy-lene blue (MB) was the best one , which has the lowest detection limit both for Mo(Ⅵ) (1× 10-9 mol/ Dand W(Ⅵ)(3× 10-10 mol/L). After adding an appropriate amount of MB,the catalytic currents for Mo(Ⅵ) and W(Ⅵ)were further increased significantly,and Ep was shifted to -0. 43V for Mo(Ⅵ) and to -0. 83 V for W(VI)respectively . The response for Mo (Ⅵ) and for W(Ⅵ) was linear over the range of 2×10-9to 4×10~7 mol/L and 5×10-10to 2×10-8mol/L respectively. Most coexisting ions (44 cations ,10 anions )studied did not interfere with the determination of Mo(Ⅵ) and W(Ⅵ),and the allowable proportion of Mo (Ⅵ) to W(Ⅵ)or in the reverse both was 1 ?25000. The proposed method has been applied to determine the molybdenum and tungsten in alloys simultaneously and directly with satisfactory results, the formation and molar ratio of the complexes,the current character, and the adsorption type ,the mechanism of electrode reaction ,and the possibilities,regularity and mechanism of the enhancement have been studied in detail and a series of constants .parameters and functions has been calculated.更多还原