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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

Versteegh, Gerard J.M., Lipp, Julius
Organic geochemistry 2019 v.133 pp. 92-102
gas chromatography-mass spectrometry, glycols, high performance liquid chromatography, marine sediments, oxidation, positional isomers
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 C32:1 keto-ol has the keto-group at the C14 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.