FLAME SPECTROPHOTOMETRIC DETERMINATION OF BORATE BASED ON DIBORANE GENERATION

Hydride (diborane) generation from borate ion and detection of the generated diborane by emission in a hydrogen diffusion flame are discussed. Borate can be converted to diborane by heating a mixture of borate (obtained by evaporating an aqueous solution of borate to dryness at 80-degrees-C) and LiAlH4 power at 160-degrees-C. Other reducing agents, such as LiH, NaH, KH and CaH2, did not produce diborane from borate on heating their mixtures up to 800-degrees-C. Also, addition of magnesium powder did not have any effect on diborane generation. When diborane was introduced into the flame, the emission spectra showed the presence of BO and BO2. To obtain this emission, diborane must be introduced from the outside fringe of the flame. The detection limit of the method was 10-mu-g B as boric acid.