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本文研究2-[2′-(6′-甲基-苯并噻唑)偶氮]-5-二甲氨基苯甲酸(MBTAMB)与钻显色反应.实验发现,在SDS存在下,pH 4.8~6.0范围内,钴(Ⅱ)与MBTAMB形成1:2络合物,其λ_(max)=654nm,表观摩尔吸光系数为1.28×10~5L·mol~(-1)·cm~(-1).该显色反应在瞬间完成,并可稳定24h.本文所拟定的方法操作简便、灵敏度高,可直接用于V_(B12)中微量钻的测定,结果满意.2 实验方法于25mL比色管中,依次加入钴(＜9μg)标准溶液,pH5.2缓冲溶液3mL,2%SDS溶液5mL及0,02%MBTAMB乙醇溶液2mL,以水定容,摇匀.在654nm处,以试剂空白为参比,用1cm比色皿测定其吸光度.3 结果与讨论3.1 吸收光谱 实验表明,在pH5.2缓冲介质中,无SDS存在时,试剂λ_(max)=530nm,Co(Ⅱ)-MBTAMB络合物λ(max)=630~650nm;有SDS存在时,试剂λ_(max)=542nm,Co(Ⅱ)-MBTAMB-SDS络合物λ_(max)-654nm,且吸光度提高约4倍,说明SDS参与了络合物组成.
In this paper, the color reaction of 2- [2 ’- (6’-methyl-benzothiazolyl) azo] -5-dimethylaminobenzoic acid (MBTAMB) 6.0, the complex of cobalt (Ⅱ) and MBTAMB forms a 1: 2 complex with λ max = 654 nm and an apparent molar absorptivity of 1.28 × 10 -5 L · mol -1 cm -1 ) .The color reaction is completed in an instant, and can be stable 24h.The method proposed in this paper is simple, high sensitivity, can be directly used for V_ (B12) trace drilling determination, the results are satisfactory.2 Experimental Method In 25mL colorimetric Tube, followed by adding cobalt (<9μg) standard solution, pH5.2 buffer solution 3mL, 2% SDS solution 5mL and 0,02% MBTAMB ethanol solution 2mL water to shake, shake at 654nm at reagent blank As a reference, the absorbance was measured with a 1cm cuvette.3 Results and discussion 3.1 Absorption spectra Experiments showed that λ max = 530nm, Co (Ⅱ) -MBTAMB (Λ) = 542nm, λ (max) -654nm of Co (Ⅱ) -MBTAMB-SDS complex and the absorbance increased about 4 times, SDS is involved in the complex composition.