Flow injection spectrophotometric determination of boron with D-sorbitol using Methyl Orange as an indicator

A spectrophotometric method for the determination of boron by flow injection, based on the complexation reaction between D-sorbitol and boric acid followed by the acid–base reaction of Methyl Orange, is described. Under the optimum conditions, the calibration graph was essentially linear up to 1.2 mg l–1 of boron (120 µl injections) and the detection limit was 0.02 mg l–1(signal to noise ratio = 3). Twenty samples can be analysed per hour with a relative standard deviation of 0.28–0.54%. The method was applied to the determination of boron in commercial eye lotions. By using a 0.6% m/v sodium chloride solution as the carrier stream, boron in sea-water samples was also determined.