PAHs in baby food: assessment of three different processing techniques for the preparation of reference materials

A feasibility study for producing a matrix reference material for selected polycyclic aromatic hydrocarbons (PAHs) in baby food is reported. A commercially available baby food, containing carrots, potatoes, tomato, white beans and meat, was spiked with the so-called 15 + 1 PAHs included in the PAHs priority list for food of the EU, at a mass fraction level of 1 μg/kg. The contaminated baby food was further processed by autoclaving, freezing or freeze drying. The homogeneity of the three materials (bottle-to-bottle variation) and their short-term (4 weeks) and long-term (18 months) stability at different temperatures were assessed. To this end, an analytical method based on a solid-liquid extraction followed by cleaning up with gel permeation chromatography (GPC) and solid phase extraction (SPE) and GC-IDMS determination, was validated in-house. It could be demonstrated that the procedure fulfilled the demands for application to the homogeneity and isochronous stability studies for the candidate reference materials targeted here. All three materials proved to be sufficiently homogeneous for the intended use. Measurements on the autoclaved material provided the most promising results in terms of envisaged shelf life, although freeze drying was also found to be a suitable processing technique for most of the investigated PAHs. These results are an important step towards the development of a matrix reference material for PAHs in a processed food matrix in a presentation very similar to routine samples.