Method development for elemental analysis in biodiesel by inductively coupled plasma atomic emission spectrometry using emulsification technique

Abstract

Various elements are used in the biodiesel production as catalysts in transesterification process or additives to improve the quality of biodiesel. The levels of each element in biodiesel therefore were needed to be regulated for the quality control of biodiesel. Commonly, acid digestion or dilution with organic solvent were used for sample preparation prior to the determination of elements by inductively coupled plasma atomic emission spectrometry (ICP-AES). Although this method is satisfactory, it has many disadvantages such as difficult handling of high viscosity of biodiesel sample, requirement of skilled operator, risk of using acid solution and organic solvent, and the needs for expensive and unstable organometallic standards for calibration. Therefore in this work, a simple and rapid sample preparation technique for ICP-AES analysis of biodiesel was developed and then the simultaneous determination of Mg, Ca, K, Cu, Mn, and Zn in biodiesel was investigated. The oil sample was emulsified with Triton X-100 as surfactant, butanol added as co-solvent and made up with deionized water in order to reduce the viscosity and become more aqueous-like in nature which would possibly allow the calibration from inorganic aqueous standard solutions. Under the optimal condition, the limits of detection (LOD) were in the range of 2.6 µg/L for Mn up to 9.6 µg/L for Cu with the relative standard deviation (RSD) of lower than 3% The proposed method has been successfully applied to determine the biodiesel samples with spike recoveries for all the studied elements within the range of 82.93-.41 102.41%