Pyrrolizidine alkaloids in herbal tea and honey: Report on the 2017 Proficiency testing scheme
Pyrrolizidine alkaloids (PAs) and their N-oxides (PANOs) are plant toxins which can enter the food chain through different paths. Two affected foods are herbal infusions and honey. This proficiency testing scheme was executed to assess the capabilities of laboratories to determine PAs. 29 laboratories from nine EU Member States plus Singapore registered. On 04. and 06.09.2017 test items and documentation were dispatched to all of those laboratories.
By the dead line of 24.10.2017 26 laboratories had reported back results and filled in a questionnaire. Test item HO (acacia honey) was fortified with six PAs/PANOs (Echimidine, Integerrimine, Intermedine, Senecionine, Seneciphylline-NO, and Senkirkine) and 23 laboratories reported results for this item. The same number of laboratories reported for test item HT (herbal infusion) which was naturally contaminated with four PAs after extraction under reductive conditions (Integerrimine, Retrorsine, Senecionine, and Senecivernine). Laboratories had to report the sums of PA and its respective PANO.
Satisfying outcomes could only be registered for Senecionine in test item HT and for Echimidine, Intermedine, and Senkirkine in test item HO with 74 %, 85 %, 85 %, and 91 %, respectively, of reported results having a z'-score smaller or equal to |2|. Only four laboratories reported for Integerrimine in both test items. Contrary to test item HT, Senecionine analysis in test item HO showed very unsatisfactory results. Of the 22 z'-scores calculated for Senecionine nine (41 %) were larger than 3. Senecivernine measurements in test item HT showed a similarly unsatisfying outcome with 47 % of reported results having z'-scores larger than 3.
Only three laboratories out of the 26 were able to test for all 10 measurands and only one reported all 10 values with z'-scores smaller or equal to |2|. Overall only five laboratories obtained satisfactory z'-scores (≤ |2|) for all their reported results. There are two groups of three isomeric PAs/PANOs each which apparently caused, for a number of laboratories, problems with quantification. This is an issue which deserves heightened attention.
The questionnaire contained queries regarding accreditation and experience, preparation conditions for the two test items, chromatographic separation conditions, detection conditions, calibration approach, and a comments section. The answers were evaluated and for selected questions their correlation to the z'-score of Senecionine in test item HO or Senecivernine in test item HT was analysed. For none of the tested questions a significant influence could be shown.
BREIDBACH Andreas;
TAMOSIUNAS Vytautas;
2017-12-21
Publications Office of the European Union
JRC109959
978-92-79-77167-5,
1831-9424,
EUR 28960 EN,
OP KJ-NA-28-960-EN-N,
https://publications.jrc.ec.europa.eu/repository/handle/JRC109959,
10.2760/219405,
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