Multi-proxy biomarker determination in peat: Optimized extraction and cleanup method for paleoenvironmental application

Organic compounds stored in sedimentary archives, such as peat bogs, can provide information on numerous processes related to paleoenvironmental changes. The application of multi-proxy methods permits to overcome the limits imposed by reduced sample size, although complex matrices need particular attention to some analytical aspects. Here, we developed and validated a method for the simultaneous determination of 27 n-alkanes, 18 polycyclic aromatic hydrocarbons and 6 sterols in peat by optimizing the extraction and cleanup procedures. The method was evaluated in terms of accuracy, recovery, detection limits and according to green chemistry assessments. In the view of future application in high-resolution multi-proxy geochemical paleoenvironmental studies, it was applied to a test batch of eight samples from the Coltrondo ombrotrophic peatland, located in northern Italy. The multi-proxy approach allowed extracting less than 1 g of dry sample. The stability of proxies over time was assessed by analyzing samples in a wide time and depth range. Results were in agreement with existing historical records and represent the first peat biomarker data for the area.