Electrophoretic Mobilities of the Isotopes of Chloride and Bromide Ions in Aqueous Solution at 25 °C and Infinite Dilution

Abstract

The electrophoretic mobilities of a few halide isotopes in aqueous solution have been evaluated at 25 °C and infinite dilution by analyzing a combination of data obtained by capillary electrophoresis (CE) and conductance data extracted from the literature. The effect of the temperature on the electrophoretic mobility has been thoroughly re-investigated to give the following temperature dependence for the chloride ion at 25 °C: 1.565%/ °C in 5×10−3 mol⋅L−1 sodium chromate + 3×10−3 mol⋅L−1 sodium borate buffer. The precise determination of the electrophoretic mobility of chloride and bromide ions, including the evaluation of their associated uncertainties, has been performed from conductance data spanning over 75 years. The electrophoretic mobilities are found to be −(79.124±0.020)×10−9 m2⋅V−1⋅s−1 for Cl− and −(80.99±0.04)×10−9 m2⋅V−1⋅s−1 for Br−. Thanks to the precise determination of the temperature contribution and the re-evaluation of conductance data, the following values have been found for 35Cl−, 37Cl−, 79Br−, and 81Br− (in 10−9 m2⋅V−1⋅s−1): −(79.18±0.02), −(78.95±0.06), −(81.04±0.04), and −(80.94±0.04).