Combination of saponification with in-tube liquid–liquid extraction and dispersive liquid–liquid microextraction for determination of polybrominated diphenyl ethers in whole milk by gas chromatography-mass spectrometry

Abstract

A simple, inexpensive and reliable analytical method was developed for the determination of polybrominated diphenyl ethers (PBDEs) in whole milk by gas chromatography-mass spectrometry (GC-MS). Matrix components such as proteins and fats in the whole milk were removed by saponification procedure and the combined PBDEs were released. Then, a simple one-step liquid–liquid extraction procedure in the centrifuge tube (in-tube LLE) was performed and PBDEs were extracted into petroleum ether. After centrifugation, dehydration and nitrogen drying of petroleum ether phase, the extract was dissolved in acetonitrile. The acetonitrile solution was directly used as dispersant for the subsequent dispersive liquid–liquid microextraction (DLLME). Under the optimal conditions, the enrichment factors (EFs) of PBDEs ranged from 270 to 307. The calibration was performed by use of matrix-matched calibration standards, the correlation coefficients were better than 0.99 and the limits of detection (LODs) ranged from 0.012 to 0.29 μg L⁻¹. The recoveries for the whole milk samples analysis spiked at 1 μg L⁻¹ were between 78% and 120% with relative standard deviations (RSDs) ranging from 1.7% to 11% (n = 5). In this study, a simple, valid and combined sample preparation method was applied in the analysis of PBDEs in whole milk sample and the satisfactory recoveries for PBDEs were obtained.