beef carcasses resized 600One of the largest source of human dioxin exposure comes though dietary intake of food of animal origin, http://www.efsa.europa.eu/. Consequently, there are extensive monitoring programs in place to identify potential contamination entering into the food chain. Current European Union regulations permit the use of GC-MS/MS and bioassay techniques for screening dioxins and dioxin-like PCBs at the level of interest in feed and food samples. The GC-MS/MS triple quadrupole is particularly suitable screening technique as isotope dilution is retained as well as the high selectivity of the MS/MS experiment. If results show samples contain high enough levels of dioxins then confirmatory analysis by a high resolution technique must be used. A good screening technique allows the same calculations of TEQ as the “Gold Standard”, provided by GC-HRMS. The TEQ result from the GC-HRMS is what is reported and the TEQ result cannot be calculated from the bioassay in the same way.

When contamination is discovered at non-compliant levels (above maximum levels allowed) the consequences can be serious and widespread. Apart from the risk to human health, contamination events can have a huge economic and political impact and receive a very high level of media attention. As this is the case, there is a strong need for organizations that interact with the food chain, from food ingredient and feed manufacturers, through to consumer suppliers and regulatory bodies to more closely monitor their own interest. The result is that the testing requirement is growing, as is the burden on confirmatory analysis capacity using high resolution (GC-HRMS) techniques.

In order for a screening technique to be truly efficient the Thermo Scientific TSQ Quantum XLS Ultra GC-MS/MS needs to be able to perform at a level that closely correlates with high resolution confirmatory techniques. The prerequisites are sensitivity, selectivity and precision. Five injections of mixed animal fat samples with 0.13 pg 2,3,7,8-TCDD/g fat gave a 12% correlation of variance. Similar results are seen in grass meal, used in animal feed.

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A direct comparison of calculated WHO-PCDD/F-TEQ in pg/g fat (or wet weight for fish) was made by analyzing the same sample extracts on both the TSQ Quantum XLS Ultra and the DFS HRMS. The data obtained are shown in the application note. You will see good correlation with HRMS data was observed in the real calculated values down to 0.5 pg/g level indicating that a highly efficient screening method is possible with TSQ Quantum XLS Ultra. The sensitivity and selectivity obtained with the technique made this possible. This means, in addition to a very low false negative rate, very few compliant samples are likely to be directed to subsequent confirmatory analysis.

The application note can be downloaded from Dioxin Screening.