Four preparations of hormonal polypeptides related to the secretin-glucagon family (secretin, glucagon, vasoactive intestinal polypeptide, gastric inhibitory polypeptide) and a preparation of pancreatic polypeptide are analyzed by reverse-phase HPLC on a #x3BC;-Bondapack column in triethylammonium phosphate buffers. The chromatographic results reveal the presence of impurities in natural peptides (VIP, GIP) and in synthetic secretin. Moreover, an important relative difference in apparent hydrophobic interactions is showed between VIP and the others peptides investigated. When a mixture of these five polypeptides is chromatographed in a 7 minute concave gradient buffer of 26 to 31 acetonitrile, VIP, GIP, S, G and PP are successively eluted in a total time of less than 20 minutes. This elution sequence does not fit with predicted retention times calculated according to the method proposed by Meek (1).
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