# Commission Regulation (EU) 2017/644 of 5 April 2017 laying down methods of sampling and analysis for the control of levels of dioxins, dioxin-like PCBs and non-dioxin-like PCBs in certain foodstuffs and repealing Regulation (EU) No 589/2014 (Text with EEA relevance), Division 6: Control of recoveries:

Extent: E+W+S+N.I.

Use of suitable internal standards with physico-chemical properties comparable to analytes of interest.
Addition of internal standards:
Addition to products (before extraction and clean-up process),
Addition also possible to extracted fat (before clean-up process), if maximum level is expressed on fat basis.
Requirements for methods using all six isotope-labelled non-dioxin-like PCB congeners:
Correction of results for recoveries of internal standards,
Generally acceptable recoveries of isotope-labelled internal standards are between 60 and 120 %,
Lower or higher recoveries for individual congeners with a contribution to the sum of non-dioxin-like PCBs below 10 % are acceptable.
Requirements for methods using not all six isotope-labelled internal standards or other internal standards:
Control of recovery of internal standard(s) for every sample,
Acceptable recoveries of internal standard(s) between 60 and 120 %,
Correction of results for recoveries of internal standards.
The recoveries of unlabelled congeners shall be checked by spiked samples or quality control samples with concentrations in the range of the maximum level. Acceptable recoveries for these congeners are between 60 and 120 %.

---
Source: https://www.legislation.gov.uk/eur/2017/644/annex/IV/division/6 (the official version)
Page: https://openlegislation.uk/eu-regulation-2017-644/annex-IV/division-6
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.