LC-MS identification of derivatized free fatty acids from adipocere in soil samples

Abstract

Free fatty acids were derivatized as amides (DFFA) by reaction with (R)-(+)-1-phenyl-ethylamine, using a simple, fast and robust reaction scheme. A HPLC method with diode array and ESI MS detection was developed for the analysis of the derivatized substances. Six fatty acids were used in the method development: myristic, linoleic, palmitic, oleic, margaric and stearic acids. Under these conditions the elution of the DFFA are well resolved with retention times raging from 6.9 to 16.0 min. Fatty acids were extracted from cemetery soil and from adipocere formation experimental soils using a Soxhlet extraction, using as solvent ether/dichloromethane (1:1). Each DFFA is characterized by three m/z peaks: molecular weight of the substance; molecular weight of a dimer of the substance; the molecular weight of the dimer plus the atomic mass of sodium. The analysis of soil samples detected the six fatty acids used in the method developed plus palmitoleic and pentadecanoic. Beside this set of eight fatty acids other 13 fatty acids were detected in trace quantities or only in some soils and some were tentatively assigned as: 10-hydroxystearic, myristoleic, heptadecenoic and arachidic acids.