A collaborative study for the performance evaluation of analytical methods for própolis. An IHC trial
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abstract
Project PDR2020-1.0.1-FEADER-031734: “Diversification and Innovation on Beekeeping Production”
Propolis is well known for its potential applications but also for its chemical
complexity, making it very hard to define quality standards for its commercialization. Every
day it is possible to find new publications on this bee product describing a new singularity,
a particular substance with high bioactivity never described or a new application. This
systematic increment in scientific information, although relevant, do not always enable a
clear comparison between samples due to the different methods and procedures used to
assess its quality parameters. To strength the scientific studies on propolis and establish
a background for future definition of standards for industry, producers and laboratories,
the Propolis Working group of the International Honey Commission, performed an interlaboratory
study to harmonize basic analytical methods and evaluate their accuracy and
robustness.
The collaborative study was accomplished by 12 laboratories from 9 countries
and a company experienced in propolis trade. The samples under analysis, representing
fifteen different origins around the globe, where fractionated and distributed to each
laboratory, and so all participants analysed the same material. Overall, six parameters
were evaluated: ashes, wax and balsamic extract on raw propolis, and total-phenolics,
flavones and flavanones on propolis extract. The results were analysed following the
international guidelines ISO 57251. Outliers were removed using Cochran’s test, to check
the homogeneity of variances at certain levels, and Grubb test’s, to check the consistency
of the laboratories average. The results revealed good reproducibility for ash, wax,
balsamic content and flavones, while for flavanones the method is clearly unsuitable.
