Detection of new long-chain mid-chain keto-ol isomers from marine sediments by means of HPLC-APCI-MS and comparison with long-chain mid-chain diols from the same samples

摘要

Long-chain mid-chain-keto-1-ol positional isomers in sediments provide important information on past environments. Unfortunately, we are unable to assess their full potential since conventional GC-MS analysis of sediment extracts is unable to reliably qualify and quantify long-chain mid-chain-keto-1-ol positional isomers, especially if these are of minor abundance. Here, we use NP-HPLC-APCI-MS to separate these isomers at baseline resolution for a given chain-length, providing a reliable alternative method to detect and quantify these molecules. We detected unknown saturated and unsaturated long-chain mid-chain-keto-1-ols and suggest that the C-32:1 keto-ol has the keto-group at the C-14 position on the basis of the patterns of abundance and retention times. Based on dissimilarities in isomer composition with that of the long-chain mid-chain diols, obtained from the same analysis, we reject the hypothesis that diagenetic oxidation of the mid-chain diol functionality is the major source of the long-chain mid-chain-keto-1-ols. We rather favor the hypothesis that the keto-ols are predominantly produced by currently uncharacterized source organisms. (C) 2019 Elsevier Ltd. All rights reserved.