Direct determination of boron in iron and steel by ion-pair reversed-phase HPLC with a laboratory-packed column

Abstract

The direct determination of trace amounts of boron in iron and steel by ion-pair reversed-phase HPLC with a laboratory-packed ODS column was studied. The laboratory-packed ODS column was prepared by packing a slurry in which ODS silica gel (particle size, 5 μm) was suspended. The iron and steel were decomposed by a mixture of hydrochloric acid and nitric acid. The decomposition solution was fumed with sulfuric acid and phosphoric acid, and then evaporated to dryness. The residue was dissolved in an appropriate volume of dilute hydrochloric acid. After an aliquot of this solution was taken into 25 cm3 of a polypropylene volumetric flask, 2.5 cm3 of 7.5 × 10-3 mol dm-3 1,8-dihydroxy-3,6-naphtalenedisulfonic acid (chromotropic acid), 2.5 cm3 of 0.275 mol dm-3 EDTA, and 2.5 cm3 of 1.0 mol dm-3 acetate buffer (pH 8.0) containing 0.5 mol dm-3 of octyltrimethylammonium bromide were added. The solution was then diluted to 25 cm3 with water. After the solution was allowed to stand for over 10 min, a 200 mm3 portion was injected into the liquid chromatograph. The eluent used was aqueous-methanol (45 55 w/w) containing 5.0 × 10-2 mol kg-1 of octyltrimethylammonium bromide and 5.0 × 10-3 mol kg-1 of phosphate buffer (pH 8.0). The eluant was monitored at 350 nm. The calibration graphs were linear over the range from 1 × 10-8 mol dm-3 to 1 × 10-6 mol dm-3. The detection limit, defined as 3σ {3-times the standard deviation of the blank value(n = 5)}, was 1.3 × 10-9 mol dm-3. The HPLC method with a laboratory-packed ODS column was applied to iron and certified steel reference materials. The boron contents in the CRMs determined by the proposed method agreed with the guaranteed ones. © 2001 The Japan Society for Analytical Chemistry.