Spectrophotometric determination of boron in food products by ester borate distillation into curcumin was studied. The sensitivity and selectivity of curcumin method were overcome by generating ester borate at proper temperature, time and pH. Boron was separated as triethyl borate by distillation in a vessel using ethanol solvent and reacted with curcumin. Distillation system reached optimum condition at temperature of 75oC and pH 5-6. Boron-curcumin complex was measured at 555 nm after 10 minutes of reaction. Separation of boron by distillation method complied with validation parameters. The standard curve was linier at concentration range of 1.2-4.8 ppm (R2=0.9995) and had molar extinction value (?) 4.7 x 105 L mol-1 cm-1 for high sensitivity level which is higher than the previous study. Percent recovery was found to be 96.09-104.92 %. Boron content in meatball and tofu products was in the range of 1.406-3.589 and 0.010-1.085 mg/kg. Ester borate distillation into curcumin has been successfully applied to the determination of boron in food products because of its high selectivity and sensitivity.

The formation of borate ester catalyzed by acid for spectrophotometric analysis of boron was investigated.  It was conducted to improve the sensitivity of the boron analysis method by optimizing the type and concentration of acid catalyst that can increase the quantity of esterified boric acid. Boron was separated from the sample matrices by dissolving the boric acid in alcohols, then dehydrated into curcumin followed by spectrophotometric determination at ? 555 nm. The influence of the type and concentration of acid catalyst against the esterification rate was observed by using acetic acid, formic acid, phosphoric acid, sulfuric acid, and hydrochloric acid with a concentration of 2.5; 4.5; 6.5; 8.5, and 10.5%. Method validation was carried out under the optimal conditions and used to measure boron and its derivatives in the crackers sample. Maximum absorbance of the boron-curcumin complex was obtained by using an H2SO4 catalyst at the concentration of 2.5%. Spectrophotometric analysis of boron through borate ester distillation gave a good recovery in the range of 99.98-104.62% and acceptable repeatability of ? 2%. The limit of detection and limit of quantification was found to be 0.316 and 1.056 mg L-1, respectively. This method has a high sensitivity level with a molar absorptivity value of 4.7x105 Lmol-1cm-1. Boron content in the cracker sample ranged from 2.936 to 4.912 mgkg-1. Keywords: acid catalyst, boron, borate ester, distillation, spectrophotometry.