5-Br-PADN光度法连续测定铸铁中铜和镍

PHOTOMETRIC DETERMINATION OF COPPER AND NICKEL IN CAST IRON WITH 5-Br-PADN AS COLOR REAGENT

研究了以溴代十六烷基吡啶和TritonX 100为增溶剂,以5 Br PADN为显色剂,在pH为9.7的氨 氯化铵介质下连续测定铜和镍的方法。铜、镍与5 Br PADN的配合物在547nm处均有较大的吸收,其表观摩尔吸光系数为εCu=3.94×104L·mol-1·cm-1,εNi=3.64×104L·mol-1·cm-1,配合物至少可稳定12h,铜、镍分别在0～10μg/10ml和0～8μg/10ml范围内服从比耳定律,方法用于铸铁中铜和镍的连续测定,结果满意。

In an ammoniacal buffer of pH 9.7, and in the presence of Triton X-100, and CPB, both of nickel(Ⅱ) and copper(Ⅱ) react with 1-(5-bromo-2-pyridylazo)-2,7-naphthalenediol (abbreviated as 5-Br-PADN) to form complexes (M∶R=1∶2) having their absorption maxima at 572nm and 532nm respectively. Summation of absorbances of the Ni(Ⅱ) and Cu(Ⅱ) complex was taken at 547nm which is the co-absorption point of both complexes. It was found that upon the addition of ethylenediamine, Cu(Ⅱ) ion is displaced from its 5-Br-PADN complex. Based on this fact, a successive determinations of summation of Ni(Ⅱ) and Cu(Ⅱ) and of Ni(Ⅱ) only after the addition of ethylenediamine. The apparant molar absorptivities (ε) of Ni(Ⅱ) and Cu(Ⅱ) complexes at 547nm were found to be 3.64×10~4L·mol^(-1)·cm^(-1) and 3.94×10~4L·mol^(-1)·cm^(-1) respectively. Beer′s law was kept in the concentration ranges of 0～8μg of Ni(Ⅱ) per 10ml of solution, and 0～10μg of Cu(Ⅱ) per 10ml of solution. The color solutions of these two complexes were stable for at least 12h. The results obtained in the analysis of some cast iron CRM′s were in good conformity with the certified values.