Consumers are increasingly interested in health food, dietary supplements and natural compounds, which command a higher price and are therefore subjected to adulteration. Methods for testing authenticity of these products are therefore required. Focus of the study is on the development of H, C and O stable isotope ratios analysis methods for this purpose. Analysis of the isotopic ratio of C, O and H in the bulk samples was performed using an isotope ratio mass spectrometer interfaced with an elemental analyser and a pyroliser. Moreover, compound specific analysis of the 2 H/1 H, and 13C/12C was done using gas chromatographycombustion\pyrolisis-isotope ratio mass spectrometry (GC-C\Py-IRMS). Stable isotope ratio of C can distinguis...