Solvent extraction-spectrophotometric determination of boron with 3,5-di-tert-butylcatechol and ethyl violet

Boric acid and 3,5-di-tert-butylcathechol formed a complex anion at pH 6.3-8.7 which was extracted into toluene as an ion pair with ethyl violet (EV); the excess EV coextracted into toluene was removed by adding 3% hydrogen peroxide. Boron was determined spectrophotometrically by measuring the absorbance of EV of the ion pair in toluene at 610 nm. The calibration curve was linear within a range of 0.043 ..mu..g of boron, and the molar absorptivity was 10.5 x 10/sup 4/ L mol/sup -1/ cm/sup -1/. This method, using the new complexing agent, was applied to the determination of boron in seawater and found to be appreciably satisfactory compared with other methods. 7 references, 3 tables, 2 figures.