High Pressure Asher (HPA-S) decomposition of biodiesel samples for elemental analysis by ICP OES

Abstract

The presence of some inorganic elements in biodiesel can compromise the fuel quality and enhance the emission of pollutants. In this context, a new procedure for biodiesel sample preparation using a high pressure asher (HPA) is presented, aiming the determination of Al, Ca, Cu, Fe, K, Mg, Mn, Na, Ni, P, Sr, and Zn, in soybean, sunflower, animal fat, cotton and castor oil, by inductively coupled plasma optical emission spectrometry (ICP OES). The digestion conditions of the HPA were optimize to digest 1.5 g of biodiesel, with HNO3 and H2O2, at a temperature of 300 °C and pressure of 435 psi, which considered the sample dilution factor, the total solids in solution and the acidity for ICP OES determinations. Analytes concentrations in these biodiesels were calculated using standard addition method. Detection limits from 0.05 to 0.7 mg kg–1 were suitable to attend biodiesel quality parameters, government policy and legislations worldwide. Therefore, the proposed procedure proved to be efficient to eliminate the major organic interferences typically present in oil based samples allowing a fast, precise, interference-free and robust analytical condition for biodiesel characterization.