Fig. 3. Isolation of pre-ecdysis-triggering hormone (PETH), ecdysis-triggering hormone (ETH) and ETH-associated peptide (ETH-AP) from epitracheal-gland extracts of pharate pupae. All three active peptides were isolated by a single reverse-phase liquid chromatography (RPLC) fractionation step using a Microsorb C₄ column (4.6x250 mm, 5 µm) and a linear gradient of acetonitrile and 0.1% trifluoroacetic acid. Molecular mass values indicated above each peak were determined by electrospray mass spectrometry.