Ion-exchange separation and spectrophotometric determination of boron in geological materials

Abstract

Various dissolution techniques were investigated for total rocks and minerals and the best approach found was alkaline fusion. Boron in silicates was rendered chemically reactive by fusion with potassium carbonate, the fusion cake was extracted with water and borate was isolated by Amberlite XE-243 boron-selective resin. The Amberlite XE-243 resin was utilized to separate microgram amounts of boron from natural waters (fresh to hypersaline) and salt cores. Borate was eluted with 2 M hydrochloric acid and determined by spectrophotometry of the carminic acid complex at 620 nm in either 94% sulphuric acid or sulphuric/acetic acid (20:80) medium, or preferably, as the azomethine-H ion-association complex at pH 5.2 (415 nm), depending on the sensitivity required. Good precision and accuracy were obtained on several international standard rocks with an average relative standard deviation of 1.37%. © 1988.