Spectrophotometric determination of boron by solvent extraction with 2-hydroxy-2-methylbutyric acid and malachite green.

A very simple and sensitive method for the spectrophotometric determination of boron was developed. Boron was found to react with 2-hydroxy-2-methylbutyric acid in weak acidic aqueous solution at room temperature to form a complex anion which can be extracted into chlorobenzene with malachite green in a single extraction; boron is determined indirectly by measuring the absorbance of malachite green in the extract at 629 nm. The calibration graph is linear over the range (7.50 × 10-7 - 2.00 × 10-5) mol dm-3 boron; the apparent molar absorptivity is 6.50 × 104 dm3 mol-1 cm-1. The method is applied to the determination of micro amounts of boron in natural waters with satisfactory results.