[en] programmable temperature vaporization injector ; large volume injection ; tandem mass spectrometry ; polychlorinated dibenzo-p-dioxin ; dibenzofuran ; food ; feed
[en] Recent developments in trapping efficiency inside ion trap mass spectrometer permitted to lower instrument detection limit (IDL). An IDL of 200 fg mul(-1) injected with a signal-to-noise ratio of 5:1 for tetrachlorodibenzo-p-dioxin (TCDD) was obtained by gas chromatography coupled to a quadrupole ion storage mass spectrometer in tandem mode (GC/MS/MS). Coupling large volume programmable temperature vaporizer (PTV-LV) injection to GC/MS/MS provides an alternative and complementary method to classical splitless-GC injection connected to high-resolution mass spectrometry (splitless-GC/HRMS) method for dioxin monitoring in food and feed. An injection volume of 10 mul was found to be the best compromise between the sensitivity requirements and the robustness required for a high throughput method. PTV-LV-GC/MS/MS and Splitless-GC/HRMS were compared by performing analysis on five different matrices such as beef fat, yolk eggs, milk powder, animal feed and serum samples covering a concentration range of two orders of magnitude (i.e. 0.2-25 ng WHO-TEQ kg(-1)). An analysis of variance (ANOVA) was carried out. Fisher tests pointed out that the method effect for all the 2,3,7,8 congeners was not significant, indicating that the null hypothesis (H-0: mu(1) = mu(2) = ... = mu(n)) was not rejected. Moreover, the interaction effects between methods and matrices were not significant for most of the 2,3,7,8 congeners. However, three congeners (2,3,7,8-TCDF; 1,2,3,4,7,8-HxCDD and I,2,3,4,6,7,8-HpCDD) were characterized by P-values lower than the significance level (alpha = 0.05). In toxic equivalence (TEQ), the study showed that no significant bias was observed between the two methods. Consequently, PTV-LV-GC/MS/MS is an attractive technique and can be used as a cost effective complementary method to HRMS for dioxin levels monitoring in food and feed. (C) 2004 Elsevier B.V. All rights reserved.