Analytical Sciences

Abstract − Analytical Sciences, 15(3), 277 (1999).

Flow Injection-Spectrophotometric Determination ofTrace Amounts of Bromide by Its Catalytic Effect on the4,4'-Bis(dimethylamino)diphenylmethane-Chloramine T Reaction
Norinobu YONEHARA, Shin-ichi CHAEN, Takashi TOMIYASU* and Hayao SAKAMOTO
Department of Earth andEnvironmental Sciences, Faculty of Science, Kagoshima University, Korimoto,Kagoshima 890-0065, Japan
A flow injection analysis method is proposed forthe spectrophotometric determination of trace amounts of bromide based onits catalytic effect on the oxidation of4,4'-bis(dimethylamino)diphenylmethane (tetrabase) by Chloramine T in aweakly acidic solution. The effects of the reagent concentrations arestudied at two pH values: 3.2 adjusted with sulfuric acid and 3.8 withacetate buffer. Although the sensitivity is slightly lower and thebackground noise is larger at pH 3.8, several ions show less interferenceat pH 3.8 than at pH 3.2. The detection limit is 1 mg l-1 andthe calibration graph for bromide is linear up to 40 mg l-1,showing a slightly negative deviation in the higher concentration range.The relative standard deviations for 1.0, 10.0 and 40.0 mg l-1of bromide are 6.4, 0.79 and 0.45%, respectively, at pH 3.2 and 8.7, 1.2and 0.38%, respectively, at pH 3.8. Bromide in water samples can bedetermined at a sampling rate of 100 h-1 with 300 ml sampleinjections. The procedure is applied successfully to the determination ofbromide in natural waters. (Keywords: Catalytic method, spectrophotometry, flow system, bromide)