Quantification of non-persistent pesticides in small volumes of human breast milk with ultra-high performance liquid chromatography coupled to tandem mass-spectrometry

Existing methods for the analysis of pesticides in breast milk involves multiple extraction steps requiring large sample and solvent volumes, which can be a major obstacle in large epidemiologic studies. Here, we developed a simple, low-volume method for extracting organophosphates, pyrethroids, carbamates, atrazine and imidacloprid from 100-200 microliters of human breast milk. We tested microwave-assisted acid/base digestion and double solvent extraction with 2 or 20 mL of 2:1 (v/v) dichloromethane/hexane, with or without subsequent solid phase extraction (SPE) clean-up. Samples were analyzed by liquid chromatography tandem mass-spectrometry. Analyte recoveries and reproducibility were highest when 100-200 microliters milk were extracted with 2 mL of dichloromethane/hexane without subsequent SPE steps. Analysis of 79 breast milk samples using this method revealed the presence of carbamates, organophsphates, pyrethroids and imidacloprid at detection frequencies of 79-96%, 53-90%, 1-7% and 61%, respectively. This study provides a simple, low-volume method for measuring pesticides in human breast milk.