The present invention relates to a method to determine the chemical composition of the hair, with special reference to possible analytes of interest like metals, vitamins, drugs, etc. The method for the determination of analytes in a hair, comprising the step of providing an hair sample and a plurality of pure analytes. The method is characterized in that it is based on processing light patterns, obtained from a spectrometer, in refracted polarized monochromatic light of said hair sample and said plurality of pure analytes, and in that the amount of each analyte present in the hair sample is calculated via unmixing.
