AbstractLaboratory refining loss, determined by the chromatographic method, is checked by a radio‐chemical procedure. Neutral triglycerides are labeled with C14‐tripalmitate and passed through an alumina column to find out if the alumina retains a percentage of them.Cottonseed oil is also labeled and, by applying the calculations of the isotope dilution analysis, the absolute neutral oil content and therefore the theoretical refining loss are determined.The theoretical and the chromatographic refining losses are compared, and a relation between them is proposed for cottonseed oils.