研究了含氟显色剂4-硝基-4′-氟苯基重氮氨基偶氮苯(NFDAAB)与铊(Ⅲ)的显色反应.在Triton X-100及0.4~2.0 mol·L-1的氨水介质中,铊(Ⅲ)与试剂形成1∶5的稳定的棕色配合物.其最大正吸收及最大负吸收波长分别位于464,563 nm.分别在两波长处采用单波长法测定及两者吸光度叠加的双波长法测定,表观摩尔吸光率分别为1.03×105,1.66×105,2.65×105L·mol-1·cm-1,双波长法具有更高的灵敏度.铊(Ⅲ)质量浓度分别在15,15,13 μg/25 mL以内符合比耳定律.加入混合掩蔽剂,用于钢厂废液、岩矿中痕量铊(Ⅲ)的测定,回收率在91.0%~99.0%之间,相对标准偏差(n=5)为1.2%~2.4%.

4-Nitro-4′-fluorophenyl-diazo-amino-azobenzene (NFDAAB) was used as a new colour reagent for thallium(Ⅲ),and conditions for the colour reaction were studied.In an ammoniacal solution of 0.4-2.0 mol·L-1,and in the presence of Triton X-100,a stable,brown-coloured coordination complex with the mole ratio [Tl(Ⅲ)∶R] of 1 to 5 was formed,with its max,positive absorption and max.negative absorption at 464 nm and 563 nm respectively.Values of apparent molar absorptivity measured at the respective wavelengths,by the conventional spectrophotometry and by the DW-spectrophotometry were found to be 1.03×105 ,1.66×105 and 2.65×105L·mol-1·cm-1.It was evident that higher sensitivity was achieved by the DW measurement.Beer′s law was held respectively in the ranges within 15 μg,15 μg and 13 μg per 25 mL of solution.The proposed method has been used in the determination of traces of Tl(Ⅲ) in samples of waste from steel plant,ores and rocks,using a mixed masking solution containing oxalic acid,sodium potassium tartrate,trihydroxyethylamine and ethylenediamine,giving values of recovery in the range of 91.0%-99.0% and RSD′s (n=5) in the range of 1.2%-2.4%.