In this work the feasibility of sequential multi-element determination of Zn, Fe, Mg, Cu, Na, K, Cr, Al and Ca in biodiesel samples by high-resolution continuum source flame atomic absorption spectrometry (HR-CS FAAS) was investigated. Biodiesel samples obtained from different sources and different chemical processes were analysed. The samples were diluted with n-propanol and water (1.4 mol L-1 HNO3) to form a microemulsion (ME) before its introduction in the HR-CS FAAS using a flow injection mode. The sample B-01 (obtained from soybean oil) was used for optimisation of the instrumental parameters. The accuracy of the proposed method was checked by analysis of certified reference material (CRM) Conostan BDM2A (for K and Na) and BDM2B (for Ca and Mg) and by comparison with acid digestion and recovery tests (for Zn, Fe, Cu, Cr and Al). The obtained results for CRM analysis showed good agreement with certified values within 95% of confidence (Student’s t-test). Recovery tests values ranged from 87-114%. The method developed for the analysis of biodiesel samples is accurate, simple, fast, and suitable for routine application.

Silica gel was chemically modified with the aromatic amines p-anisidine, p-phenytidine and p-phenylenediamine, using grafting reactions. The resulting modified silicas were characterized by infrared spectroscopy and N2 adsorption/desorption isotherms. The organic groups were covalently immobilized in a monolayer form. These modified silicas were investigated as adsorbents for Pb2+, Cu2+, Cd2+ and Ni2+ in aqueous and ethanol solutions. In a general way, the adsorption capacity values for all adsorbents presented the following sequence: Pb2+ >> Cu2+ <FONT FACE=Symbol>@</FONT>Cd2+ <FONT FACE=Symbol>@</FONT> Ni2+. Adsorption studies for all adsorbents, in competitive medium, showed better selectivity for Cu2+ and Pb2+ in aqueous medium and for Pb2+ in ethanol solution. Desorption studies were carried out using HCl and HNO3 as eluents.