Desenvolvimento de métodos de preparo de amostras para a subsequente determinação de metais em macroalgas.

Abstract

In this work was proposed the use of two methods for sample preparation: oxygen pressurized microwave radiation assisted digestion (MW-O2-AD) and microwave radiation assisted UV-digestion (MW-UV-AD) for macroalgae from the Antarctic for further determination of As, Cd, Cr, Cu, Mn, Mo, Ni, Pb, V and Zn by inductively coupled plasma mass spectrometry (ICP-MS) and inductively coupled plasma optical emission spectrometry (ICP OES). For MW-O2-AD method were evaluated 0.5, 1, 2, 3 and 7 mol l-1 HNO3 solutions at pressures of 1, 5 and 10 bar of O2. These same solutions were used in the MW-UV-AD and for 0.5 and 1 mol l-1 HNO3 was evaluated the use of H2O2. To compare the performance of proposed methods, the samples were also digested with concentrated HNO3 by microwave radiation assisted digestion (MWAD). Using MW-O2-AD (3 mol l-1 HNO3 and 5 bar of O2) and MW-UVAD (2 mol l-1 HNO3) methods the metals concentration was in agreement (above 91%) with the results obtained for digesteds using concentrated HNO3 for almost analytes. The accuracy of the proposed methods was evaluated using certified reference materials BCR 060 (Aquatic plant) and NIST 1515 (Apple leaves) and the agreements with certified values were above 92% for all analytes. Using the proposed methods the residual carbon content was always lower than 10% and the limit of detection was between 0.001 and 1.45 μg g-1 for all analyts. Additionally, the use of dilute HNO3 in both methods reduced the blank values and improved the LODs.