A novel and eco-friendly analytical method for phosphorus and sulfur determination in animal feed

An eco-friendly method for indirect determining phosphorus and sulfur in animal feed by ion chromatography was proposed. Using this method, it was possible to digest 500 mg of animal feed in a microwave system under oxygen pressure (20 bar) using only a diluted acid solution (2 mol L−1 HNO3). The accuracy of the proposed method was evaluated by recovery tests, by analysis of reference material (RM) and by comparison of the results with those obtained using conventional microwave-assisted digestion. Moreover, P results were compared with those obtained from the method recommended by AOAC International for animal feed (Method nr. 965.17) and no significant differences were found between the results. Recoveries for P and S were between 94 and 97%, and agreements with the reference values of RM were better than 94%. Phosphorus and S concentrations in animal feeds ranged from 10,026 to 28,357 mg kg−1 and 2259 to 4601 mg kg−1, respectively.