以5’-硝基水杨基荧光酮（5’-NSAF）为显色剂，建立了分光光度法测定钴的新方法。研究表明：在pH为9.2 的NH₃.H₂O-NH₄Cl 缓冲介质中，在表面活性剂TritonX-100 作用下，钴（Ⅱ）与5’-硝基水杨基荧光酮能生成一种红色配合物，配合物在546 nm处有最大吸收，表观摩尔吸光系数为3.7*10⁴ L.mol^-1.cm^-1，检出限（3s/k）为5.64*10^-3 mg/L，钴（Ⅱ）的质量浓度在0~0.5 μg/mL范围内与吸光度A有良好的线性关系。方法应用于维生素B₁₂注射液中钴含量的测定，结果满意。

A new method for the determination of cobalt was established by spectrophotometry with 5’-nitro-salicylfluorone(5’-N-SAF)as coloring agent. In the buffer solution of NH₃.H₂O-NH₄Cl at pH 9.2, cobalt(Ⅱ) reacted with 5’-N-SAF and formed a red complex in the presence of TritonX-100. The apparent molar absorptivity was 3.7 *10⁴ L.mol^-1.cm^-1 at 546 nm; the detection limit(3s/k)was 5.64 *10^-3 mg/L; Beer's law was obeyed for the mass concentration of cobalt(Ⅱ)in range of 0~0.5 μg/mL. The method was applied to the determination of cobalt content in Vitamin B₁₂ injections, and the results were satisfactory.