Total and inorganic mercury determination in biodiesel by emulsion sample introduction and FI-CV-AFS after multivariate optimization

Abstract

An automated procedure for total and inorganic mercury determination in biodiesel by CV-AFS was studied. The samples were introduced directly as oil-in-water emulsions in a flow injection manifold followed by cold vapor generation coupled to atomic fluorescence spectrometry (FI-CV-AFS). After irradiation with an UV source, organic mercury (e.g. MeHg+ and PhHg+ among others) was decomposed. Mercury vapors were generated using an acidic SnCl2 solution in a continuous flow system and were then determined. This strategy reduced sample handling, avoiding sample contamination and analyte losses. The limit of detection was calculated as 0.2 g Kg-1 (0.03 g L-1 for the emulsions) and the relative standard deviation was better than 8% at levels of 3.0 g L-1 in the emulsion, calculated from the peaks obtained. The accuracy was verified by comparing the results with a total microwave-assisted digestion.