Marking of material, marked material and process of authentication or dilution determination

A method for determining whether a material is genuine by determining presence of a blend of components which vary in spectral position and/or intensity according to variation of pH, the blend of components having been added to the material as a marker, the components in the blend of components not being already associated with the material prior to being added as a marker, comprising:

• a) preparing an aliquot of a solvent containing a sample of the material at a first pH;
• b) measuring spectral position of the fluorescence of the aliquot of a) at one or more excitation wavelengths;
• c) adjusting the pH of the aliquot of b) to a second pH wherein at least one component of the blend of components has at least one of a different spectral position and/or intensity at the second pH than the first pH;
• d) measuring spectral position of the fluorescence of the aliquot formed in c) at one or more excitation wavelengths;
• and
• e) comparing a spectral position of the fluorescence between the fluorescence measured in b) and the fluorescence measured in d) with known spectral positions of at least two components of the blend of components at the pH's used in a) and c) to thereby determine whether the at least two components of the blend of components is present in determining whether the material is genuine.

A method for authenticating if a material has been subject to diversion or adulteration by determining the concentration of two or more components of a blend of components that has been added to the material as a marker, the components in the blend of components not being already associated with the material prior to being added as a marker, at least one of the two or more components of a blend of components having a fluorescence which varies in intensity according to variation of pH, comprising:

• a) measuring fluorescence intensity of an aliquot of a solvent in the absence of the components at an excitation wavelength as a noise base measure (NBM).
• b) preparing an aliquot of the solvent containing a sample including a known amount of the material at a first pH;
• c) measuring fluorescence intensity of the aliquot of b) at one or more excitation wavelengths;
• d) adjusting the pH of the aliquot of b) to a second pH wherein at least one component of the blend of components has a different intensity than at the first pH;
• e) measuring fluorescence intensity of the aliquot formed in d) at one or more excitation wavelengths;
• f) comparing a difference in fluorescence intensity between the fluorescence measured in c) and the fluorescence measured in e) for at least two components of the blend of components with a known difference in fluorescence intensity of the components at the pH's used in a) and c) to thereby determine the presence or concentration of at least two components of the blend of components to permit a determination of diversion or adulteration of the material.