Spectrophotometry of Boron in Steels with Curcumin by Flow Injection Analysis

The determination of boron in steels was investigated by flow injection analysis (FIA) using curcumin, which has been used for the conventional spectrophotometry of boron. The conventional curcumin method requires the evaporation of the sample solution to dryness in the procedure. Therefore, the curcumin method has been not adapted for FIA. The use of acetic anhydride could alternate the evaporation process in the conventional method. This enables us to apply curcumin to FIA to remove the coordinated aqueous molecule from boron. The flow system was composed with five channels including the concentration column (Amberlite IRA743). The 2 × 10-3M curcumin (acetic acid: acetic anhydride=1 : 4 v/v), the mixed acid (sulfuric acid: acetic acid: acetic anhydride =1 : 6 : 13) and 0.1 M sodium hydroxide were used to form boron curcumin complex as the reagent solutions. By using the concentration column, boron was separated from matrix iron (10000 ppm), and was concentrated to 13-fold in 0.42 ml of 10% sulfuric acid as eluent. The obtained calibration curve was linear over the range of 0-100 ppb in the sample solution. The limit of determination (10 Sb) was 2 ppb in the sample solution. The analytical results for boron in standard steel samples (B: 0.001-0.0106%) show good agreement with the certified values.