# Commission Regulation (EC) No 152/2009 of 27 January 2009 laying down the methods of sampling and analysis for the official control of feed (Text with EEA relevance), Division 2: Principle

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

For the determination of the total tryptophan, the sample is hydrolysed under alkaline conditions with saturated barium hydroxide solution and heated to 110 oC for 20 hours. After hydrolysis internal standard is added.
For the determination of free tryptophan, the sample is extracted under mild acidic conditions in the presence of internal standard.
The tryptophan and the internal standard in the hydrolysate or in the extract are determined by HPLC with fluorescence detection.

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Source: https://www.legislation.gov.uk/eur/2009/152/annex/III/division/G/division/2 (the official version)
Page: https://openlegislation.uk/eu-regulation-2009-152/annex-III/division-G/division-2
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.