Abstract
Extraction and esterification conditions were examined for the analysis of dipeptides in sediments by gas chromatography (GC) coupled with mass spectrometry (MS). It was found that extraction by shaking with water at 60℃ for 1h and esterification in 1.5M HCl-methanol at room temperature for 3h were satisfactory conditions under which a small portion (<0.2%) of L-valylglycine (L-Val-Gly) decomposed as well as only a trace amount of hexaglycine (<0.04%) and polyglycine (<0.02%) decomposed to glycylglycine. We applied the method to the surface sediment sample (0-2.5cm) from Tokyo Bay. Stereoisomers of alanylalanine, Val-Gly and glycylvaline were separated by an optically active GC column and their identifications were made by GC-MS, showing apparent dominances of the L-isomers. The four dipeptide concentrations ranged from 1.6 to 5.3nmol g-1. The dipeptides detected from the sediment sample are very likely those extant in the sediment mainly derived from proteins during the early stage of diagenesis but not those produced by the degradation of polypeptides in the course of the analytical procedure employed.
