The resulting signal at the detector is a spectrum that represents a molecular fingerprint of the sample. The usefulness of infrared spectroscopy stems from the fact that chemical structures leave unique spectral fingerprints that allow easy identification. However, these fingerprints are not always unique, especially if the sample contains too many functional groups. In summary, NMR and FTIR may not be sufficiently informative compared to XRD. Thus, each technique has its advantages and disadvantages.