Determination of essential and toxic elements in maternal milk collected in Taubaté, São Paulo State, Brazil

Abstract

This work is concerned with the investigation of oligoelements and heavy metals in the maternal milk (colostrum and mature milk). The specific objectives are: (i) to verify the performance of the analytical procedures; (ii) to compare the composition of the colostrum and the mature breast milk and (iii) to verify if the maternal milk is contaminated by toxic elements. Throughout the year of 2004, 79 samples of colostrum and 16 samples of breast milk were analysed (Ca, Cr, Cd, Cu, Fe, Mg, Mn, Ni, Se, Pb and Zn). The samples were submitted to an acid digestion in a closed system, and flame atomic absorption (FAAS) and/or electro thermal atomic absorption spectrometry (GFAAS) were used for the determination. Tests were performed on standard NIST-certified milk-powder to validate the reliability of subsequently collected analytical data. The reproducibility varied from 1.9 to 12.2% (FAAS) and from 2.8 to 9.2% (GFAAS). It was found significant difference at 5% level between the concentrations in colostrum and mature milk only for calcium (129.33 and 208.85 mg L-1, respectively) and for iron (1.414 and 2.561 mg L-1, respectively). The lead concentrations in colostrum (0.209 mg L-1) and mature milk (0.136 mg L-1) were very high compared to the ANVISA (a Brazilian regulatory agency), that establishes a maximum of 0.05 mg kg-1. Analytical methodologies developed here show excellent performance using both FAAS and GFAAS. The maternal milk contains all essential oligo-elements. The lead high level suggests necessity of a strong control of food and regions contamination to avoid its presence in maternal milk.