In recent years, several high-profile contamination crises have raised concerns over dioxin levels in a variety of food products. In December 2008, the Irish government recalled all pork products made in the Republic of Ireland after the discovery of dioxins in slaughtered pigs. Tests on some of the Irish pork products showed dioxin levels up to 200 times the recognized safety limit. This was followed by the Chinese government’s December 9th announcement banning all imports of pork from Ireland after some of the meat was found to be contaminated with elevated dioxin levels. These crises dealt a massive blow to consumer confidence in these regions; government agencies and food processors needed to source instrumentation that could accurately identify and contain the spread of dioxins in the global food supply.
Polychlorinated biphenyls (PCBs) and dioxins are suspected carcinogens. They are fat soluble, and more than 90% of human exposure to them comes though our daily food intake, specifically through the consumption of meat, fish, and dairy products.1 Because dioxins, which build up primarily in fatty tissues over time, are neither readily metabolized nor excreted, even low levels of dioxin exposure can mean accumulation to dangerous levels over time.
Dioxin’s effects on human health have been difficult to determine, due to a lack of controlled dose experiment data; however, tests on animals have demonstrated strong links between dioxins and birth defects, cancer, liver toxicity, immunosuppression, and endocrine disruption. The chemical is also believed to have a dramatic impact on the nervous, immune, and reproductive systems.
Regulations and Food Testing
The findings on the adverse health affects of dioxins led regulatory bodies such as the U.S. Food and Drug Administration (FDA), the U.S. Environmental Protection Agency (EPA), and the Association of Official Analytical Chemists to produce detailed reviews and testing guidelines on dioxins and dioxin-like substances, while the World Heath Organization charted tolerable daily, weekly, and annual dioxin intake levels. The EPA set maximum levels for dioxins in food; its directives require limits of quantitation 80% lower than the lowest reported level in EPA Method 1613 Rev. B. These new guidelines mean that much more demanding detection, selectivity, and sensitivity levels are required during the testing process in order to confirm the presence of dioxins.
The FDA developed its own dioxin strategy, aimed at obtaining data on base levels of dioxin in food and animal feed, identifying dioxin contamination sources that can be eliminated or significantly reduced, and estimating dietary dioxin exposure.3
The high-resolution gas chromatography and high-resolution mass spectrometry (HRGC/HRMS) method, which is capable of increased levels of sensitivity, selectivity, and detection, has been cited as the most effective analytical technique for this application. The EPA and many European regulatory bodies require HRGC/HRMS dioxin testing methods as standard. To demonstrate the effectiveness of HRGC/HRMS in low-level analysis of the polychlorinated dioxins, the following experiment was performed utilizing the Thermo Scientific DFS High Resolution GC/MS system.
An experiment was devised to test the capabilities of HRGC/HRMS instruments in the analysis of dirty matrix samples. Measurements were carried out on the Thermo Fisher Scientific DFS High Resolution GC/MS system coupled to a Thermo Fisher Scientific TRACE GC Ultra gas chromatograph equipped with a split/split-less injector.
Samples were injected using the company’s TriPlus Autosampler. The injection volume was 2mL of each sample measured. A TRACE TR-5MS GC column with dimensions 60m length, 0.25mm ID, and 0.1mm film thickness was used for the analysis.
Injection was performed using the “hot needle technique,” in which the empty needle is heated up in the injector for two to three seconds before injecting the sample, thus eliminating any discrimination of higher boiling congeners. The mass spectrometer was set up in the multiple ion detection (MID) mode at a resolution of 10,000 (10% valley definition).