Measurement of Amorphous Ferric Phosphate as an Assessment of Iron Bioavailability

A method for measuring amorphous ferric phosphate in complex salt mixtures and animal diets is described. The procedure uses citrate solutions for extraction of salt mixtures and tartrate solution for extraction of prepared diets. Iron in the solution is then determined colorimetrically. Crystalline ferric phosphate, which has no iron bioavailability, is not extracted by either solution. Thus, the procedure can determine if the amorphous form, which has a high iron bioavailability, is present. The procedure was tested on gypsy moth artificial diet and Wesson salt mixture, which is a salt supplement of the diet.