1—（2—吡啶偶氮）—2—氨基萘的合成及钴的分光光度测定

合成了新偶氮化合物1-(2-吡啶偶氮)-2-氨基萘(PAAN),并研究了它与钴的显色反应,在pH4.0～5.0的醋酸-醋酸钠缓冲溶液中,Co~(2+)与PAAN形成红色螯合物,λ_(max)=550nm.ε达1.0×10~5L·mol~(-1)·cm~(-1)(乙醇-水溶液)和5.16×10~4 L·mol~(-1)·cm~(-1)(OP-水溶液),钴与显色剂的组成比为1:2.钴量在0～11μg/25ml范围内遵守比耳定律.该显色反应选择性好.仅Ni~(3+).Fe~(3+).Cu~(2+).Pd~(2+)干扰,可通过加入盐酸酸化至1mol/L,破坏上述离子的配合物而消除,在不加任何掩剂的情况下.测定了土壤、茶叶和维生素B_(12)中的钴,结果满意.

SYNTHESIS OF PAAN AND SPECTROPHOTOMETRIC DETERMINATION OF COBALT

A new azo compound 1- (2-pyridylazo)-2-amino naphthalene (PAAN) had been synthesized. The color rection of this azo compound with cobalt was studied. It indicated: PAAN reacts with cobalt to form a red complex at pH 4. 0-5. 0 in buffer medium of acetic acid-sodium acetate. The maxium absorbance wavelength of the complex is 550 nm and its apparent molar absorptivity is 5. 16X 104 L-mol-1 cm-1. The composition ratio of the complex is Co ( I ) : PAAN= 1: 2, Beer's law is obeyed for the amount of cobalt within the range of 0-11 ng/25ml. This reaction has good selectivity. Only Nickle ( II ), Iron (III) and Copper (II) etc interfere the determination, but it can be eliminated by acidifiation to 1 mol/L with 6 mol/L hydrochloric acid and heating to destroy the complexes which have been fromed by interferntial metal ions mentioned above. Without any masking agent, This method was used to determintion of cobalt in soil, tea and vitamin Bi2, all the results were satifactory.