Assessment of uncertainty sources of free gossypol measurement in cottonseed by high-performance liquid chromatography

Gossypol is a polyphenolic component found in pigment glands of whole cottonseed, it is toxic in its free-form (FG) to livestock farm animals. It can be degraded through the preparation and extraction of the tested sample, leading to inaccurate quantification of FG content in animal diets. The primary size of the laboratory samples, the particle size of the analytical samples, and interval of time between grinding and solvent extraction were tested as uncertainties of the sample preparations. The efficiency of extraction, accuracy, linearity, matrix effects, limits of detection and quantification were assessed in the chemical analysis. The chemical analysis contributes as a minor source of uncertainty in analysis, despite the occurrence of matrix effects. Solvent soaking time can be considered as an effective uncertainty source; at least 16 h of soaking in acetone should be applied to extract FG from glands. Trueness and precision are the accuracy parameters most affected in the steps prior to the chemical analysis. The reduction of particle size as the increase of the interval of time between grinding and chemical analysis affected the trueness of results. On the other hand, precision was affected by the sample size of analytical and laboratory sample preparation. The best practices to reduce the uncertainty in FG analysis increase the confidence of cottonseed use as an animal feed source regarding its toxicity, improving animal health and the safety of animal products intended to human consumption.