Evaluating Matrix Effects in the Analysis of Polycyclic Aromatic Hydrocarbons from Food: Can These Interferences Be Neglected for Isotope Dilution?

A procedure to evaluate matrix effects was systematized and applied to the analysis of polycyclic aromatic hydrocarbons in roasted coffee and cocoa beans. The analytical method relied on gas chromatography coupled to mass spectrometry with isotope dilution (GC-IDMS). Once the regression assumptions were confirmed, the slopes and intercepts obtained for traditional and matrix-matched calibration curves were compared by the t test, with or without combined variances, depending on the profile of the residual variances. Matrix effects were considered when the slopes and/or intercepts differed significantly. The occurrence of matrix effects diverged for the studied matrices. No matrix effects were detected for roasted coffee using GC-IDMS, whereas significant effects were observed for cocoa beans. An original discussion related to these findings was presented, based on the differences in the chemical compositions of the matrices and the instrumental conditions. These results serve as a warning to current practices in validation of methods that involve IDMS and highlight the importance of the matrix effects evaluation, even when using an isotope dilution approach.