1982 Volume 31 Issue 9 Pages 479-483
A highly sensitive and simple method for the spectrophotometric determination of boron was developed. Boron was found to react with hydrobenzoin in weak alkaline medium to form a complex anion extractable into benzene with crystal violet, and the measurement of the absorbance of crystal violet in the extract at 600 nm enabled the determination of boron indirectly.The recommended procedure is as follows: Take an aliquot of the boron solution (2.0 × 10-4 mol 1-1) into a 10-ml test tube. Add 1 ml of carbonate buffer solution (pH 9.4) and 0.25 ml of crystal violet solution (1.0 × 10-2 mol 1-1), and dilute the mixed solution to 4 ml with deionized water. Shake the solution with 4 ml of benzene solution containing hydrobenzoin (2.0 × 10-2 mol 1-1) for 2 min. Measure the absorbance of the organic phase at 600 nm using a 10-mm glass cell against benzene. The calibration curve obeyed Beer's law on the concentration range from 2.5 × 10 -6 mol l-1 to 2.5 × 10 -5 mol l-1 of boron, and the apparent molar absorptivity was 3.0 × 104 l mol-1 cm-1 at 20°C. It was found that many kinds of co-existing ions interfered with the determination. However, this method was applicable to the determination of boron in sea water when chloride ion and cations such as Ca (II) and Mg (II) were previously eliminated by treating the sample solution with Ag2O and cation exchanger resin. The proposed method is a very simple and rapid one, because this method does not require apparatus other than common laboratories and the evaporation to dryness of sample or removal of the excess of reagent.
