Determination of organochlorine pesticides (OCPs) in breast milk from Rio Grande do Sul, Brazil, using a modified QuEChERS method and gas chromatography-negative chemical ionisation-mass spectrometry

The food chain is the main source of exposure to humans by organochlorine pesticides (OCPs) due to the bioaccumulation. Breast milk can accumulate OCPs, so this matrix is often used as an environmental bioindicator. The currently available methods for the determination of several OCPs and metabolites in breast milk involve, in general, multi-step sample preparation and quantification techniques with low selectivity, high cost and much time and labour. Thus, a fast and efficient method based on sample preparation using the quick, easy, cheap, effective, rugged and safe (QuEChERS) method combined with gas chromatography coupled to mass spectrometry with negative chemical ionisation (GC-NCI-MS) was developed, validated and applied for determination of 16 OCPs and metabolites in breast milk samples. The extract was cleaned by dispersive solid-phase extraction (d-SPE) using MgSO4 and C18, evaporated in a Turbovap (R) system, redissolved and analysed by GC-NCI-MS. The method was validated showing acceptable recoveries (72-118%) and precision (RSD <19%). Method limits of detection (LODs) and quantification (LOQs) ranged from 0.75 to 7.5ngg(-1) and from 2.5 to 25ngg(-1) lipid, respectively. The method was successfully applied to 20 samples of breast milk from different regions of the Rio Grande do Sul state, Brazil, of which 75% contained residues below the LOQs.