Abstract: A multiple-vial, rotating, sample container assembly for Raman spectroscopy comprises a container with two or more receptacles formed therein, which are suitable for positioning two or more vials inside the sample measurement area of a spectrometer. The openings are located such that when the container is rotated, the vials inside the holder are alternately positioned in the laser beam path, and the Raman scattering from each sample material is co-collected during the same measurement period. The rotation of the container (RPM) is sufficiently fast so that the material in each vial is measured many times during a sampling period, thereby ensuring a high degree of reproducibility in measuring the combination of vials. For a quantitative or peak comparison method, one vial contains a reference material. This material may be pure (100% of a compound), a dilution of the material in a solvent (such as water), or a combination of materials. Another vial contains the sample, or material to be evaluated.