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|What is the differnce between CALUX® and HRGCMS?|
Data for dioxins analyzed by a
screenings method, like DR CALUX® are expressed in CALUX-TEQs, while
data for dioxins analyzed by HRGC-HRMS are expressed in WHO-TEQs. Is there a
difference? Are these different expressions comparable?
This question is raised frequently, and rightly so, because these different expressions may suggest apparent differences, which creates some level of confusion. These different expressions of data originate from the scientific discussions on an international level. Momentarily the consensus opinion is that WHO-TEQ should only be used for data that are generated by making use of the WHO-consensus list of TEF values for calculating the WHO-TEQ of a sample. This is the case for all analytical-chemical methods, like HRGC-HRMS, which actually measure concentrations of individual congeners on a, e.g. pg/g lipid basis. These concentrations are consecutively converted into calculated total toxic potencies (WHO-TEQ). In fact, in this calculation step concentration data are converted into total toxic potencies, using the WHO-list of TEF values. Since WHO has reassessed the WHO-TEF numbers for individual congeners several times, it is also required to indicate which list is used (i.e., 1989 (I-TEQ); 1998, or 2006 WHO-TEQ).
The EU accepted screenings methods for dioxins, like DR CALUX®, directly measure the total toxic potency of dioxins and therefore do not require a conversion step of the data, using a WHO-TEF list. Therefore, CALUX derived data should not be expressed as WHO-TEQ but rather as CALUX-TEQ which is equivalent to WHO-TEQ. The equivalency of CALUX-TEQ to WHO-TEQ is based on the following arguments and observations:
1) The consensus values by WHO for toxic equivalent potencies (TEF values) for the various congeners is mostly based on their equivalent liver toxicity data, which also forms the basis for the DR CALUX®, since this screenings method uses enzyme induction as a measure of liver toxicity using the H4IIe cell line, which has also been used by Safe et al., 1989 for the development of the whole TEF concept.
2) The TEF values for individual dioxin congeners measured by DR CALUX® are highly comparable to the consensus TEF values determined by the WHO for the same congeners;
3) The CALUX-TEQ values for samples are comparable to WHO-TEQ values determined and calculated by HRGC-HRMS for the same samples
In conclusion, the only real difference between CALUX-TEQ and WHO-TEQ concerns a difference in the method of determination and/or calculation. CALUX directly measures the total toxic potency, while HRGC-HRMS firstly determines the concentration for each individual congener (pg/g) which are consecutively converted into toxic potencies which are added up to a total toxic potency, expressed as WHO-TEQ, using the WHO-TEF list for the calculations. Therefore the numbers generated by both methods are not equal, but are equivalent to each other. In addition, EU guidelines demand a reconfirmation by HRGC-HRMS of each analysis result by DR CALUX that exceeds the EU maximum limit value. Therefore, in the end, all final product evaluations are based on WHO-TEQ regarding the question whether, or not the maximum limit values are exceeded.