COMPARISON OF DIGESTION METHODS FOR DETERMINATION OF As, Cd, Se, Fe and Pb IN DIFFERENT SAMPLE MATRIX

Sample preparation is one of the most important step of an analysis procedure. Usually it takes almost 61% of analysis time and it is responsible for 30% of the total analysis error. In this study, three instruments for digestions were tested by using the same amount of sample and nitric acid. For this purpose, 3 certified reference materials (CRM) constituted by different matrices were evaluated: protein, carbohydrate and fat matrix. To evaluate the matrix effects (residual carbon), the calibrations curves (CC) was prepared by using digested L-cysteine (Sigma, USA) or HNO3 5 % v/v as diluent. After analysis by ICP-MS (Agilent 7900, Hachioji, Japan), similar slopes for both CC demonstrated minimal matrix effects except for Pb where there were an increase of recovery from 65% to 97%.