This document specifies a method for the determination of free gossypol, extractable by acidified acetonitrile/water, in cottonseed, cottonseed products and compound feeds by liquid chromatography with tandem mass spectrometry (LC-MS/MS). The method described in this document has been successfully validated in the range of 69 mg/kg to 5 950 mg/kg by collaborative trial in the following matrices: cottonseed, cottonseed products (cake/meal, hulls) and compound feeds for bovine, porcine and poultry. NOTE It is possible to reach quantification limits of approximatively 5 mg/kg in compound feeds. The method might be applicable at lower and at higher concentrations than the concentration range validated in the collaborative trial. However, this needs to be assessed by in-house validation.