This document specifies a method for the determination of the chelated micronutrient content and the chelated fraction of a micronutrient, in organo-mineral fertilizers, having an organic matrix based on vegetal residues (cocoa shells, grape residue, soybean residue, etc), algae extract, and animal meal (feather, bones, blood, etc) and containing UVCB, EDDHA, EDDHMA, HBED, EDDHSA micronutrients by the treatment with a cation exchange resin. The limit of determination of the chelated micronutrient content highly depends on the specific electrical conductivity of the sample, on the amount of nutrient present, and varies between 0,005 % in simple matrices with high amounts of micronutrient, and 0,5 % in more complex cases (see 9.1).