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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NaClO_3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NaClO_3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NaClO_3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~(-8)mlo/L,检出限分别为1×10~(-9)和3×10~(-10)mol/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。
In the sulfur-phosphorus mixed acid medium containing EDTA and Bromobenzene-glycolic acid (Br-BHA), the molybdenum (VI) -Tungsten (VI) -Br-BHA complexes produced less sensitive polarographic currents . The addition of NaClO_3 resulted in a sensitive catalytic current [2.3 and 3 times more sensitive than that of BHA, respectively), and the peak potentials (Ep) shifted to -0.44V and -0.78V, respectively. More than 10 kinds of easily protonated organic dyes and 8 kinds of cationic surfactants were studied systematically to further sensitize the above catalytic current, of which methylene blue (MB) was the best. Without NaClO_3, adding MB, the original complex current slightly reduced, E_D no significant change. However, when NaClO_3 was added, the polarographic catalytic current was further sensitized with Ep values of -0.43V and -0.83V, respectively. The linear ranges of molybdenum (VI) and tungsten (VI) were 2 × 10 -9 ~ 4 × 10 -7 and 5 × 10 -10 ~ 2 × 10 -8, respectively. The detection limits were 1 × 10 -9 and 3 × 10 -10 mol / L, respectively. Most of the coexisting ions (44 cations, 10 anions) do not interfere with the determination, [Mo (VI)]: [W (VI)] or vice versa, 1: 25000 do not interfere with each other. The method has been applied to the direct determination of molybdenum and tungsten in the alloy, pure iron and other samples with satisfactory results. In this paper, the complex ratio, current characteristics, electrode reaction mechanism, possible rules and mechanism of sensitization were studied in detail, and a series of related constants and parameters were calculated.