Determinação de poluentes orgânicos persistentes (pops) em leite materno: desenvolvimento e aplicação de método analítico empregando GC-NCI-MS

Abstract

Persistent Organic Pollutants (POPs) receive this designation because of the time that remain unchanged in the environment. From the 1960s there was already evidence of the presence of these compounds in sediment, breast milk, fish and eggs. The food chain can be considered a source of contamination of humans by these compounds due to bioaccumulation. The fat contained in milk can accumulate POPs, so this matrix has been used as environmental bioindicator. The currently available methods for the determination of these compounds in breast milk involve, in general, multi-step sample preparation and quantification techniques with low selectivity, have high cost and are time consuming. Thus, this study aimed to develop a fast and efficient method based on sample preparation using the QuEChERS method combined Gas Chromatography coupled to Mass Spectrometry with negative chemical ionization (GC-NCI-MS). In this work we optimized the sample preparation step for the determination of 15 POPs in breast milk (Alpha HCH, beta HCH, gamma HCH, hexachlorobenzene, heptachlor, andrin, dieldrin, endrin, 2,4 DDE, DDT, endosulfan alpha, beta endosulfan, endosulfan sulfate and mirex) using 6 mL of sample extracted with 6 mL of acetonitrile. In the partition step was used 2.6 g MgSO4 and 0.6 g of NaCl. The extract clean-up was performed by dispersive solid-phase extraction of 4 mL of extract and 600 mg of MgSO4 and 200 mg of C18. The extract was evaporated in a Turbovap system and redissolved in 200 μL acetonitrile for the determination by GC-NCI-MS. The method was validated showing linearity for the 15 evaluated compounds. Recoveries of the analytes ranged between 62 and 120% with precision within the acceptable range (RSD <19%). The limits of detection for breast milk, in terms of fat percentage, ranged from 0.75 to 7.5 ng g-1 and the method limits of quantification ranged from 2.5 to 25 ng g-1. The method was applied to 20 samples of breast milk from different regions of the Rio Grande do Sul state, of which only 25% were not contaminated by the studied POPs and the others showed values below the LQ. It is important to emphasize that this is an unpublished work in the area of POPs determination in breast milk by GC-NCI-MS, and could be a basis for future works in this area.