Abstract: The invention relates to a method for the identification and quantification of one or more biomolecules in a sample containing a mixture of substances, wherein said method comprises the steps of, a) providing a sample which contains one or more biomolecules, b) providing a reagent for the analysis of biomolecules according to Formula I (A-Y-PRG) wherein, A may be present or absent and when A is present, A is H or constitutes at least one functional group for the reversible, covalent or non-covalent binding to a support material, whereby Y is a group comprising at least one chelate function for metals, preferable low in isotopes, and whereby PRG is a reactive group for the selective binding of biomolecules to be analyzed, c) coupling the one or more biomolecules from step a) to the reagent of step b), d) selecting the one or more biomolecules labeled in step c) under the employment of a functional group for the reversible, covalent or non-covalent binding to a support material and removal of the one or more un