[Presence of residues and pollutants in human milk]. / Presencia de residuos y contaminantes en leche humana.

The contamination of human milk by xenobiotics is a common problem worldwide which is affected by the geographical, climate-related, cultural and socioeconomic variations in each individual location. Public health policies have dealt with this situation by means of ongoing monitoring and restrictive legislation in order to reduce the damaging effects on the populations and the environment, objectivatable data however being recorded particularly in the developing countries. Overall and individual aspects of waste and contaminating oganochlorines, organophosphorates, antibiotics, polychlorate biphenyls, dioxins and furans, their content values, toxic effects studies and the maximum limits permitted under international legislation are highlighted.

Development and characterisation of a molecularly imprinted polymer prepared by precipitation polymerisation for the determination of phenylurea herbicides.

New materials based on molecularly imprinted polymers (MIPs) have been developed for use as sorbents in solid phase extraction to preconcentrate some urea herbicides. In the preconcentration step, different molecularly imprinted polymers were tested using methacrylic acid (MAA) and 2-(trifluoromethyl)acrylic acid (TFMAA) as functional monomers, and linuron and isoproturon as templates. The best results were obtained when the polymer was synthesised using MAA with isoproturon as template. Another parameter evaluated was the way in which the polymer was obtained. We observed that the imprinted polymers obtained by precipitation displayed a greater capacity to retain the phenylureas. Studies conducted using scanning electron microscopy (SEM) revealed that the bulk polymerisation method is far from ideal owing to the random shape and size distribution of the particles obtained, whereas when polymerisation was carried out in precipitation microspheres were obtained. In order to confirm the interaction between the functional monomer and the template, 1H NMR (CD2Cl2) analyses were conducted. The results obtained suggest that the hydrogen and/or nitrogen of the amino group of the template would be involved in the formation of hydrogen bonds with the functional monomer. The imprinted polymer obtained by precipitation polymerisation with MAA as functional monomer and isoproturon as template can be applied to preconcentrate phenylureas when the sample is dissolved in toluene. The proposed methodology was employed to evaluate polymer selectivity towards humic acids and towards other herbicides.