Aliphatics in Soil Organic Matter in Fine‐Clay Fractions

Fine‐clay fractions were separated from three agricultural soils and extracted sequentially with n‐hexane, chloroform and supercritical n‐pentane. The resulting extracts were analyzed by field ionization (FI) and field desorption (FD) mass spectrometry (MS). The major components indentified included C 11 to C 94 n‐alkanes, C 13 to C 34 n‐fatty acids, n‐C 16 and n‐C 24 diols, and C 38 to C 67 n‐alkyl monoesters. Minor components were C 22 , C 32 , and C 34 n‐alcohols, C 27 and C 29 sterols, C 56 to C 91 n‐alkyl diesters, C 83 to C 99 n‐alkyl triesters, and C 17 to C 21 unsaturated monocarboxylic acids in extracts of one clay only. The highest molecular weight compound identified was the C 99 n‐alkyl triester (m/z 1478). Especially noteworthy was that: (i) similar aliphatics were extracted from the three clays, (ii) the compounds identified were typical of components of natural waxes, which appear to be present in the organic matter in fine‐clay fractions, and (iii) the soft ionization mass spectrometric methods employed were found to be eminently suitable for the identification of medium to high molecular weight aliphatics in the organic matter in fine‐clay fractions.