Determination of 16 phthalate acid esters in infant formula by gas chromatography-tandem mass spectrometry

Abstract

A method was established for the determination of 16 phthalate acid esters (PAEs) in infant formula by gas chromatography-tandem mass spectrometry (GC-MS/MS). PAEs in infant formula samples were homogenized by deionized water, extracted with acetonitrile, and purified by a solid-phase extraction (SPE) method using primary secondary amine (PSA) sorbents. The separation was performed on a DB-5 MS UI (30 m×0.25 mm×0.25 μm) capillary column. Effects of different elution solvents on alumina/PSA and PSA SPE columns were investigated. Fair recoveries of 16 PAEs were achieved on the PSA column upon elution by mixed n-hexane-acetone (60:40, v/v). All the 16 PAEs were quantified by matrix-matched isotopic-dilution mass spectrometry (IDMS); the 16 PAEs showed linear relationships in the concentration range of 0.01-2.0 mg/kg with linear coefficients (R2) greater than 0.9996. The limits of detection (LODs) and quantification (LOQs) were in the range of 0.15-2.5 μg/kg and 0.50-8.33 μg/kg, respectively. The recoveries of the 16 PAEs, obtained using the IDMS method, were 96.1%-104.0% with relative standard deviations (RSDs) lower than 3.3% (n=5). These results established the method described here as sensitive and precise for the simultaneous determination of 16 PAEs in infant formula, even at trace concentrations.