FIELD: physics.SUBSTANCE: group of inventions relates to the marking of goods. Method of marking a material includes adding a blend of components, having different fluorescent characteristics, to said material, the blend of components not already associated with this material, and where at least one of the components of the blend is characterised by fluorescence, varying in spectral position and / or intensity according to variation of pH, the blend of components being included in the material in an amount sufficient for its qualitative and / or quantitative determination. Method for determining the authenticity of a material by determining the presence of the blend of components, which vary the spectral position and / or intensity according to variation of pH, wherein said blend of components is added to the material as a marker, the components of the blend not being already associated with said material. Method for confirming whether a material has been altered or tampered with by determining the concentrat
