Spectrophotometric determination of boron by flow injection analysis

Abstract

Spectrophotometric determination of boron existing as boric acid in water was examined with H-resorcinol {1-(2, 4-dihydroxy-1-phenylazo)-8-hydroxynaphthalene-3, 6-disulfonic acid} by flow injection analysis. Carrier solution (deionized water) and reagent solution were propelled by double plunger pump (flow rate : 0.6 ml/min), and sample solution (320 μl) was injected into a carrier stream. The reagent solution was prepared by dissolving 0.096 g of H-resorcinol in 1 1 of ammonium acetate buffer solution (50 g/l, pH 5.5) containing 3.72 g of EDTA. The two streams were mixed in 16 m long Teflon tubing (0.5 mm i.d.), and the mixture was flowed through a flow cell (36 μl; 1.5 mm i.d. × 20 mm), at which the absorbance of boron-H-resorcinol complex was detected (λ=510 nm). The linear relationship between the peak height and concentration of boron was obtained in the range of 0 to 1 ppm. The detection limit was 5 ppb (S/N=2). The sampling rate was 30 samples per hour. Generally ions co-existing in river and sea waters did not interfere with the determination of boron by adding EDTA solution.