We report here the development of an analytical protocol for the specific isolation of isoprenoid and branched glycerol dialkyl glycerol tetraethers (i-and br-GDGTs, respectively) of microbial origin from soil samples for radiocarbon dating. This protocol comprises an extraction step followed by several chromatographic steps combining different techniques (silica gel column chromatography, high performance liquid chromatography and thin layer chromatography). Radiocarbon dating of these two series of compounds, isolated from a surface sample and a deep horizon sample (40-50 cm) from a soil profile, shows that i-and br-GDGTs in the deep sample have a comparable mean residence time (MRT), despite their different biological origin. These MRT are, however, lower than those measured for the soil organic matter (SOM) and for the different compartments of SOM. This result suggests that i-and br-GDGTs originate from microorganisms using the same carbon source, made of a combination of ancient and recent organic matter. It can also be envisaged that these compounds originate from both recent and ancient microbial populations. These preliminary results suggest that the use of (palaeo) proxies based on the distributions of GDGTs might be questionable in the case of soils or, at least, that caution is needed when interpreting soil GDGT signals in terms of (palaeo) environmental reconstructions.