Pyrolysis-compound specific isotopic analysis (P-CSIA: Py-GC- (FID)-C-IRMS) of carbohydrate derived structures

The pyrolytic behavior of two commercial sugar samples arising from a C3 plant (cane sugar) and a C4 plant (beet sugar) were studied using both conventional analytical pyrolysis (Py-GC/MS) and ¿13C pyrolysis compound specific isotope analysis (P-CSIA: Py-GC- (FID)-C-IRMS). Major pyrolysis compounds identified by Py-GC/MS were Furfural-5-methyl (MF), Furfural-5-hydroxymethyl (HMF) and Levoglucosane (LV). Expected differences in bulk ¿13C (¿) were found between the sugar from C3 and C4 plants but also for the main specific compounds released after pyrolysis with ¿13C values for cane sugar: MF -14.35±0.89 ¿, HMF -11.22±0.54 ¿ and LV -11.44±1.26 ¿; and for beet sugar: FM -24.65±0.89 ¿, HMF -22.07±0.41 ¿ and LV -21.74±0.17 ¿. Outstanding significant linear regressions were observed when analyzing the ¿13C isotopic signature for the main specific sugar pyrolysis compounds in mixtures of beet sugar in cane sugar (20%, 40%, 60%, 80% and 100%): MF ¿13C (¿)= -0.093sugar (%) - 14.66 (R² = 0.94); HMF ¿13C (¿)= -0.11sugar(%) - 11.51 (R² = 0.99) and LV ¿13C (¿)= -0.10sugar(%) - 12.31 (R² = 0.97). The MF, HMF and LV are structures commonly found in pyrolysates from a wide range of organic materials sharing a common carbohydrate precursor (saccharides). Our results indicate that pyrolysis compound specific isotopic analysis (P-CSIA) of such structures can be used as markers surrogated to the estimation of organic matter turn-over times -mainly for ¿fast C pools¿- in complex matrices like soils and sediments.

Peer Reviewed