High-performance liquid chromatographic resolution of synthetic opiate and "anti-opiate" peptides from human plasma

An assay system using reversed-phase high-performance liquid chromatographic (HPLC) resolution of synthetic anti-opioid peptides (AOPs) and opioid peptides (OPs) was developed. Samples were diluted with trifluoroacetic acid, loaded onto Sep-Pak C18 cartridges, eluted, dried, and redissolved in ethanol-acetic acid-water. Retention-time consistency was established, and high levels of synthetic AOP and OP recovery, generally higher than 80%, were achieved. In a single HPLC run synthetic enkephalins, dynorphins, and beta-endorphins were separated even when extracted from human plasma using a volatile mobile phase which yielded fractions totally compatible with quantitation by radioimmunoassay. Combining the resolution of HPLC with the sensitivity of radioimmunoassay (RIA) may facilitate simultaneous measurement of numerous neuropeptides in body fluids such as plasma and cerebrospinal fluid.