Determination of pesticides in milk-based infant formulas by pressurized liquid extraction followed by gas chromatography tandem mass spectrometry

An efficient and selective automated analytical method for the determination and quantification of a selected group of 12 organochlorine and organophosphorous pesticides in milk-based infant formulas has been developed. The samples were extracted by pressurized liquid extraction (PLE) and analysed using GC-MS/MS. The use of alumina as the fat retainer in the PLE extraction cell, together with the application of an injector temperature program during the GC injection process, avoided typical matrix interferences without the application of additional cleanup steps. Mean recoveries of between 70 and 110% were achieved for most of the compounds, except for chlorpyrifos methyl (50%), vinclozoline (48%), fenitrothion (56%) and procymidone (53%), with relative standard deviations ranging from 9 to 17%. Low limits of quantification were obtained for the studied compounds, from 0.01 to 2.6 μg kg⁻¹, thus guaranteeing their accurate determination within the rigorous requirements established for baby food. The validated method was applied to a pilot monitoring study in Spain. Twenty five samples of different brands of powdered infant formulas were obtained from supermarkets. Positive findings of endosulfan I, endosulfan II, fenitrothion, chlorpyrifos ethyl and bifenthrin were detected at concentrations ranging from 0.03 to 5.03 μg kg⁻¹.