Full Description ADOPTED_FROM:EN 17270:2019 This document method is applicable for the determination of theobromine in compound feed by liquid chromatography with UV detection in the tested range of 27 to 307 mg/kg. This method has been validated using complementary compound feed for adult dogs and complementary compound feedstuff for horses. The actual working range may extend beyond the tested range. Alternative chromatography conditions using liquid chromatography tandem mass spectrometry (LC-MS/MS) are also provided for the validated range of 49 to 307 mg/kg. This method has also been shown to be fit for purpose for the determination of theobromine in baking chocolate by both HPLC-UV and LC-MS/MS.