Separation of boron from fumarolic condensates by the methyl borate distillation method for the isotopic analysis

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  • 同位体比測定のための火山ガス凝縮水中のホウ素の蒸留分離
  • ドウイタイヒ ソクテイ ノ タメ ノ カザン ガス ギョウシュク スイチュウ

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Abstract

A new simple extraction method of boron from volcanic emission products, especially gaseous ones, without changing their isotopic ratio, was investigated. The procedure was as follows. To the fumarolic condensate (10 ml) in a teflon beaker, 13 ml of 1.0 M sodium hydroxide and 1 ml of 30% hydrogen peroxide were added. The mixture was diluted with 6 ml of water (the sodium hydroxide concentration was about 0.1 M), and evaporated on a hot plate of 94°C. The residual cake was dissolved into water and the volume was made to 4 ml. By this process, sulfite ion was oxidized to sulfate and the boron was concentrated by a factor of 2.5. In a separate flask, 50 ml of methyl alcohol together with 12 ml of concentrated sulfuric acid and 0.4 g of aluminum sulfate (to convert fluorides in the sample solution to a non-volatile form), was predistilled to remove any dissolved boron. The concentrated boron sample solution (3 ml) was then transferred into this flask which was heated in a mantle heater at (95100)°C. Methyl alcohol vapor generated from a separate flask was introduced into the flask and methyl borate was distilled out from this solution. The distillate (40 ml) was absorbed into 10 ml of 0.1 M sodium hydroxide. This solution was transferred into a Teflon beaker, and evaproated to dryness on a hot plate. The cake thus obtained was dissolved into about 100 ml of water, and was passed through a polyethylene column packed with Bio Rad 50W-X12 ion-exchange resin in the hydrogen form into a teflon beaker. The column was washed with about 20 ml of water. Sodium hydroxide solution (0.01 M) was added until the atomic ratio of sodium to boron was 1.5, and it was evaporate to (0.20.3) ml. The boron isotopic ratio in this sample was determined by the surface ionization method. The recovery of boron from samples containing 100 μg of boron was found to be higher than 97%. Fractionation of boron isotopes was negligible. The precision for the determination of the boron isotopic ratio was found to be ±0.2% as the coefficient of variation.

Journal

  • BUNSEKI KAGAKU

    BUNSEKI KAGAKU 27 (8), 481-485, 1978

    The Japan Society for Analytical Chemistry

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