Determinação de POPs e agrotóxicos em leite materno empregando cromatografia a gás acoplada à espectrometria de massas com ionização química negativa (GC-NCI-MS)

Abstract

The Stockholm Convention was the first global attitude trying to preserve human health and the environment of the indiscriminate use of persistent organic pollutants (POPs), especially pesticides, which are characterized by being lipophilic and can bioaccumulate in fatty tissues including breast milk. However, POPs represent only a part of the chemicals with the potential for environmental pollution and human as new substances are constantly being developed and released into the environment. In this work, the sample preparation step was optimized based on the results of the factorial design 32 varying solvents and sorbents. The method was validated for 54 compound using a mixture of hexane:acetone for extraction, clean-up by dispersible solid phase extraction (d-SPE) using activated Florisil® and determination by gas chromatography coupled to mass spectrometry using negative chemical ionization (GC-NCI-MS). The matrix effect was compensated by the use of extracted analytical curve. The validation of the method showed satisfactory results for linearity, accuracy (recovery between 71.9 and 119.8%) and precision (RSD <29%). An evaporation step of the extract concentrated the analytes enabling low detection (3 to 26 ng g-1 of fat) and quantitation (9 to 86 ng g-1 of fat) limits. The method was applied to 20 samples of breast milk collected in different regions of Rio Grande do Sul state, Brazil, all of which contained at least one of the studied compounds. With principal component analysis of the results, it was possible to relate the pesticides detected in relation to the city of origin of the samples and the number of nursing mother's pregnancies. Considering that breast milk is a complex matrix, the analytical method was effective for the determination of trace levels of POPs and pesticides in breast milk and can be applied in monitoring analysis of human exposure to these contaminants.