铂、钯、钴合金中钴的选择性测定

建立了EDTA络合锌盐滴定选择性测定Co的方法,考察了不同类型的酸及酸浓度对EDTA络合Co(Ⅲ)及滴定终点的影响,研究了提高方法选择性的条件.结果表明:于0.1～1.0 mol/L HNO_3、0.1～1.0 mol/L HCl、0.024～0.24 mol/L H_2SO_4和0.001～0.078 mol/L HClO_4酸浓度内,EDTA-Co络合物稳定,且滴定终点敏锐;测定5.00～20.00 mg Co(Ⅲ),相对误差-0.20%～+0.24%,样品加标回收率99.40%～100.40%;采用联合掩蔽剂能消除30余种共存元素的影响;方法准确度高,选择性好,操作简便,适用性强,已用于Pt、Pd、Co合金中质量分数为5%～75%Co的测定,结果满意.

Selective Determination of Cobalt in Platinum,Palladium and Cobalt Alloys

A method for selective determination of cobalt using EDTA complex and zinc salt titration was proposed. The effects of the kinds of acid and their acidity on EDTA complex of cobalt (Ⅲ) and titration end-point were studied. The conditions for improving selectivity of the method were also discussed emphatically. The results indicated that the EDTA-Co complex is stable and the titration end-point is sensitive in the acidity range of 0.1～1.0 mol/L HNO_3,0.1～1.0 mol/L HCl,0.024～0.24 mol/L H_2SO_4 and 0.001～0.078 mol/L HClO_4. The relative error is -0.20%～+0.24% for the determination of 5.00～20.00 mg cobalt(Ⅲ) and the recovery of Co in samples with the addition of standard cobalt is 99.40%～100.40%. More than 30 elements are noninterference using combined masking reagent. The proposed method has high accuracy,good selectivity,convenient operation,better applicability and was applied to determine cobalt in platinum,palladium and cobalt alloys containing 5wt%～75wt% cobalt with satisfactory results.