Activating effect of ligands in the catalyzed reactions and its application to the catalytic determination of trace amounts of elements

建立了流动注射分光光度法连续测定铜和铁的方法。它是基于铜(II)和铁(III)对双氧水氧化N，N‘-双(2-羟基-3-磺丙基)邻甲苯(HTS)生成深色染料(λ_&lt；max&gt；=670 nm)的催化作用。在铜(II)催化的反应中，2，2‘-联喹啉、2，9-二甲基-4，7-二苯基、1，10-邻菲咯啉二磺酸和2，9-二甲基-邻菲罗啉(NECOUP)是有效的活化剂。另一方面，2，2‘-联吡啶、1，10-菲咯啉(Phen)和8-羟基喹啉-5-磺酸在铁(III)催化的反应中起到了活化剂的作用。在磷酸和三乙醇胺掩蔽剂存在下，将含有新钴或邻菲咯啉的样品溶液引入流水线，无需任何分离步骤，即可选择性地测定铜(II)(1-30 ng m l；-1)和铁(III)(2-50 ngm l；-1&gt；)，无需任何分离步骤。1，2-二羟基苯-3，5-二磺酸的存在提高了钒(IV，V)催化反应的速度，显著提高了方法的灵敏度。钒(IV)和钒(V)的测定范围为0.01~3.0 ng·ml~(-1)·g~(-1)，进样速率为30h~(-1)·g~(-1)。方法的检出限(S/N=3)为0.01ngmlt；-1，10次测定的相对标准偏差分别为1.4%和1.6%；钒(IV)和钒(V)的10次测定的相对标准偏差分别为1.4%和1.6%。用乙二胺-N，N，N‘，N’-四(亚甲基膦酸)作掩蔽剂可抑制金属离子的干扰。该方法用于水样中钒的测定，结果满意。

A spectrophotomeric flow-injection method has been developed for the successive determination of copper(II) and iron(III). It is based on the catalytic effect of copper(II) and iron(III) on the hydrogen peroxide oxidation of N,N'-bis(2-hydroxy-3-sulfopropyl)-o-tolidine (HTS) to produce an intensely colored dye (λ_<max> = 670 nm). In the copper(II)-catalyzed reaction, 2,2'-biquinoline, 2,9-dimethyl-4,7-diphenyl^1, 10-phenanthroline disulfonic acid and 2,9-dimethyl-phenanthroine (neocup) were found to be effective activators. On the other hand, 2,2'-bipyridine, 1,10-phenanthroine (phen) and 8-hydroxquinoline-5-sulfonic acid acted as activators in the iron(III)-catalyzed reaction. By introducing the sample solution containing neocup or phen into flow line in the presence of phosphoric acid and triethanolamine as masking agents, copper(II) (1-30 ng ml^<-1>) and iron(III) (2-50 ng ml^<-1>) can be selectively determined with sampling frequency of 20 h^<-1> without any separation procedures.A sensitive flow-injection photometric method has been also proposed for the catalytic determination of vanadium(IV, V), based on the catalytic effect of vanadium(IV, V) on the oxidation of HTS by bromate. The presence of 1,2-dihydroxybenzene-3,5-disulfonate increased the rate of vanadium(IV, V)-catalyzed reaction and significantly enhanced the sensitivity the method. Vanadium(IV) and vanadium(V) in the range 0.01-3.0 ng ml^<-1> were easily determined with sampling rate of about 30 h^<-1>. The limit of detection (S/N = 3) was 0.01 ng ml^<-1> and the relative standard deviations were 1.4 % and 1.6 % for ten determinations of 0.2 ng ml^<-1> vanadium(IV) and vanadium(V), respectively. Interferences from metal ions could be suppressed by the use of ethylenediamine-N,N,N',N'-tetrakis(methylenephosphonic acid) as a masking agent. The proposed method was successfully applied to the determination of vanadium in water samples.