Opioid peptides and other neuropeptides are expensive and purity is not always sufficiently established. These peptides can be prepared either by conventional methods or by the Merrifield's method. Peptides synthesized by conventional methods can be more easily purified and are generally crystalline compounds. The main disadvantages of the conventional methods is, they are very labor intensive, slow and costly. Solid phase methods provide a much faster way of synthesizing a number of analogs and the drawback of this method is that only small quantities of peptides can be easily synthesized. The peptides are generally not as pure and extensive purification of the products may be required. By whatever the method these peptides are obtained, their purity should be thoroughly established and their purity analyzed prior to their use. However, the chemical complexity of peptides makes the analysis of peptides very difficult and demands utilization of innovative, extremely specific and sensitive methods. In order to provide pure and crystalline opioid peptides to researchers NIDA has awarded two contracts to synthesize (one contract by solid phase synthesis and the other by solution methods) and maintain an inventory of about 20-30 peptides. Through these contract NIDA plans to supply chemically pure, racemization-free peptides and at the same time maintain capability to rapidly synthesize, on demand, new ligands to support research and development efforts. The present contract seeks to establish the purity of the peptides synthesized through the two NIDA contracts, and also peptides obtained by NIDA for Medications Development. The contractor will characterize the peptides, monitor stability and batch to batch variation, determine the peptide content, and develop sensitive analytical methods such as liquid chromatography/mass spectrometry (LC/MS) for a selected number of peptides.