Analysis Chemistry 1 Optimization for Determination of Esters in Biodiesel Oil by Spectrophotometric Method Mangkorn Kitiphatmontree, Kesanee Yindeechat, Watchara Youlamyai and Arekaradate Retvereeyasakul

The simple spectrophotometric method for the determination of esters has been developed. The procedure is based on the quantitative determination of ferric hydroxamate generated from the reaction of esters, hydroxylamine hydrochloride in basic solution at 120 °C, and ferric chloride. The formed complex was monitored through absorbance at 517 nm. The parameters affecting the absorbance value were explored for optimum analytical performance. The optimum conditions were 1.50 mL of 0.5 M hydroxylamine hydrochloride, 0.40 mL of 6 M sodium hydroxide, 1.00 mL of 3 M hydrochloric acid and 0.50 mL of 5 % ferric chloride. The method exhibits linear response up to 7.50% wt. and a detection limit of 0.23% wt. The linear range and working range were used at the same range 1.25 to 7.50% wt. The proposed method can be applied to biodiesel (B100) for measuring the esters quantity in the percentage unit of biodiesel oil.