Fig. 3

Multidimensional gas chromatogram showing 18O-labeled phosphorus oxoacids extracted from the residues. The atomic mass units 214 (×100) and 304 (×150) were selected for this multidimensional chromatographic representation. Partial GC×GC chromatogram of the separation of the two minor phosphorus oxoacids is shown top left. The unassigned peaks result from the silylation agent (BSTFA: TMCS 1%) that was injected in excess compared to the blank analysis (Supplementary Fig. 3) to avoid sample loss