Solvates are a common occurrence in the pharmaceutical industry.  Their identification is important in process development, the final performance of the drug substance and for patenting purposes.  Slurrying anhydrous or hydrate crystals in solvents can result in solvates.  Alternatively, some materials are found to crystallize only as solvates with their non-solvated counterparts being either meta-stable or amorphous. 13C SSNMR can be used to distinguish a solvate from surface solvent.  Cross polarization (CP) in conjunction with magic angle spinning (MAS) is a routine technique in solid state to get high resolution 13C spectra in the solid state.  The CP/MAS spectra typically discriminate against the more mobile regions in the sample.  This is because in rigid regions of the sample the cross polarization efficiency is better owing to the good contact between 1H and 13C reservoirs.  On the other hand, direct polarization (DP) spectra acquired with short recycle delays (~1s) tend to discriminate against the more rigid regions in the sample.  Crystal Pharmatech researchers have designed experiments based on CP and DP dynamics that will unambiguously determine whether a solvate exists in your system.