The determination of microgram and sub-microgram amounts of boron : II. The separation of boron by distillation and the evaporation of distillates

Methyl alcohol distillates containing μg amounts of boron may be evaporated without loss of boron by first adding water, sodium hydroxide and glycerol. The resulting residues can be used directly in the curcumin absorptiometric methods previously described. The distillation techniques developed over the last decade by the United Kingdom Atomic Energy authority are briefly described, as these can be used for the separation of boron from practically all types of sample, including organic matter after it has been ashed with lime. In all cases aqueous solutions of the samples are made slightly acid (pH 1.5–5) and evaporated nearly to dryness Residues are then treated with methyl alcohol in one of three ways according to their properties. It is essential to use all-silica distillation apparatus and platinum dishes for collecting distillates. Notes are given of other precautions necessary to minimize contamination from reagents and other sources. The methods are rapid and suitable for routine analysis on up to 10 g of sample. Under favourable conditions, the limit of detection is of the order of 0.01 p.p.m. of boron. A precision of better than 5% can be obtained with amounts exceeding about 0.2 p.p m.