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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.

European legislation has recently established a list of 15 priority polycyclic aromatic hydrocarbons (PAHs) to be monitored in foodstuff. Thus, the accurate determination of these compounds has become a highly relevant issue. The fact that some of these European Union (EU) PAHs differ from those typically analysed, requires the re-evaluation of the instrumental conditions for the proper determination of the new target compounds. In this study, the influence of the stationary phase and dimensions of the GC capillary column on the chromatographic resolution of the 15 EU PAHs has been investigated. Apolar (DB-5 type) and medium polar (DB-17 type) stationary phases with different lengths and film thickness have been evaluated for the separation of the target compounds, with special emphasis on those coelutions involving isomers such as the three benzofluoranthenes included in the EU PAHs. In addition, the influence of the injection technique and the column dimensions on the recovery of the high molecular mass PAHs has been studied. A programmable temperature vaporising (PTV) injector has been used in three different operational modes and the results were compared to those obtained using on-column injection. The experimental parameters involved in the injection step were optimised by using experimental design.

A method based on gas chromatography (GC) separation followed by ion trap tandem mass spectrometry detection in EI mode (ITD-MS/MS), using isotope dilution, was developed for the determination of ten native polybrominated diphenyl ethers (PBDEs) and four (13)C(12)-labeled congeners in biological (fat tissue and human serum) and food samples. The highest-mass fragment ions were used as precursor ions for those congeners with molecular ions with m/z values higher than the maximum of the instrument. In these cases (hepta-BDEs and (13)C(12)-hexa-BDEs) no fragmentation was achieved under the experimental conditions employed. Repeatability (lower than 9%) and reproducibility (lower than 13%), expressed as relative standard deviation (RSD, n = 3 and 4, respectively), were satisfactory. Similarly, the coefficient of variation (n = 4) of the isotopic ratio between the two most abundant product ions was lower than 10 and 6% for native and labeled congeners, respectively. To evaluate the feasibility of the method, the optimized isotope dilution GC/ITD-MS/MS method was used for the quantitation of selected PBDE congeners in different samples including adipose tissue, human serum and foodstuff samples, from three inter-laboratory comparative exercises, covering a wide range of concentrations. A solid-phase extraction procedure, previously developed for PCB determination in small-size bird serum samples, was successfully applied to quantification of PBDEs in 1 mL samples of human serum.