Development and validation of two analytical methods for urea determination in compound feed, including pet food, and yeast using high-performance liquid chromatography coupled with fluorescence detection and tandem mass spectrometry

Urea is authorised in the European Union (EU) as feed additive for ruminants. Because of its high molecular nitrogen content, it a substance potential protein adulteration non-ruminant feed. The EU defines spectro-colorimetric method an official control determination urea feed, whereas Association Official Analytical Chemists (AOAC) United States recommends enzymatic method. Discrepancies between results obtained by these different approaches have been reported, especially at low concentrations. Therefore, we developed and validated two methods compound including pet food, yeast (Saccharomyces cerevisiae) over wide concentration range using high-performance liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) fluorescence detection (HPLC-FLD) compared performance commercial enzyme kit. Limit (LOD) limit quantification (LOQ) were found to be 3 8 mg kg−1 LC-MS/MS 2 7 HPLC-FLD, respectively. For both methods, variation coefficients ranged 1.4% 7.2% ruminant used reference material well spiked samples complete chicken, food dogs cats, yeast. Recovery rates from 86% 105%. real poultry, wet dry cats amounts < LOD 200 relative feedingstuff moisture content 12% found. In comparison kit, newly proved less time-consuming sample preparation more stable regarding matrix effects.