Simultaneous determination of phenolic pollutants in dairy products held in various types of packaging by gas chromatography−mass spectrometry

Abstract

The U.S. Environmental Protection Agency (EPA) has deemed phenolic compounds priority organic pollutants. These compounds can reach milk and dairy products at different production stages from farm to packaging. In this work, we developed a procedure involving ultrasound-assisted extraction from milk and dairy products, and subsequent clean-up of the extract and preconcentration of the analytes by continuous solid-phase extraction (SPE) for their quantification by gas chromatography−mass spectrometry. The proposed method was used to detect and quantify a total of 21 phenolics including phenols, alkylphenols, bisphenols and chlorophenols in milk and dairy products. The method was validated in terms of recovery (85–108%), linearity, matrix effects (slight, <20%), precision (relative standard deviation < 11%), and limits of detection (6–63 ng/kg). Then, it was used to analyze nineteen milk samples and as many dairy product samples. The most detected analytes were bisphenol Z, bisphenol A and 4-t-butylphenol, which were found in the samples at concentrations spanning the ranges 96–1100, 30–1400 and 310–2100 ng/kg, respectively. The contaminants were present mainly in milk and dairy products packed in polystyrene terephthalate (PET), multilayer packaging (carboard/polyethylene/‌aluminum) or polystyrene (PS) packaging. By contrast, the samples packed in glass containers contained very low levels of the phenolics.